Showing 1–50 of 94 results for author: Bose, S

Technical Proposal for the Atom Interferometer CERN Experiment (AICE) Facility

Authors: Gianluigi Arduini, Nadja Augst, Mark G. Bason, Charles Baynham, Andrea Bertoldi, Gianfranco Bertone, Diego Blas, Daniela Bortoletto, Sougato Bose, Roberto Ales Bozzi, Oliver Buchmueller, Tamara Alice Bud, Clare Burrage, Sergio Calatroni, John Carlton, Vassilis Charmandaris, Maria Luisa Chiofalo, Pierre Cladé, Jonathon Coleman, Fabio Corsanego, Albert De Roeck, Arnaud Devienne, Fabio Di Pumpo, John Ellis, Pierre Fayet , et al. (57 additional authors not shown)

Abstract: We present the technical proposal for the Atom Interferometer CERN Experiment (AICE), a $\mathcal{O}(100)$ m vertical atom interferometer to be installed against the wall of the PX46 access shaft to the LHC. AICE is conceived as a versatile and flexible long-baseline atom-interferometry facility whose primary scientific goal is probing for bosonic ultralight dark matter (ULDM) in a mass range inac… ▽ More We present the technical proposal for the Atom Interferometer CERN Experiment (AICE), a $\mathcal{O}(100)$ m vertical atom interferometer to be installed against the wall of the PX46 access shaft to the LHC. AICE is conceived as a versatile and flexible long-baseline atom-interferometry facility whose primary scientific goal is probing for bosonic ultralight dark matter (ULDM) in a mass range inaccessible to other experiments, with a secondary goal of pioneering the exploration of gravitational waves (GWs) with frequencies in the range ${\sim}$0.03-3 Hz as a pathfinder for future longer-baseline detectors. The initial configuration employs ultracold $^{87}$Sr atoms in a single-photon 698-nm interferometer with three shaft-based atom sources in a multi-source gradiometer geometry, supported by one surface reference source for laser stabilisation and diagnostics, to target scalar ULDM. Operation with $^{88}$Sr will give sensitivity to axion-like particles (ALPs), vector ULDM with $B-L$ couplings and violation of the principle of equivalence, while a $^{171}$Yb upgrade will improve the sensitivity to $B-L$ couplings and equivalence violations. Probing the Einstein equivalence principle (EP) and measuring $α$ will proceed in parallel with the ULDM searches. A conceptual feasibility study and a detailed technical implementation study have established that PX46 is a uniquely mature and implementation-ready site, with no technical showstoppers. Completing site preparation works during LS3 would enable the subsequent installation and operation of AICE without impacting HL-LHC operations. The detector design builds on the VLBAI and MAGIS experiments and the AION-10 Technical Design Report, scaling the strontium gradiometer architecture to the $\sim$100 m baseline. AICE is endorsed by the TVLBAI Proto-Collaboration, comprising 57 institutions in 22 countries. △ Less

Submitted 19 August, 2026; originally announced August 2026.

Comments: 170 pages, 64 figures, 24 tables. Technical Proposal for CERN review process of AICE

Report number: CERN-PBC-REPORT-2026-001

The FLARE Facility

Authors: Hantao Ji, Jongsoo Yoo, Peiyun Shi, Euichan Jung, Kush Maheshwari, Adam Robbins, Sunghyun Son, Adam Stanier, Yang Ren, Sayak Bose, Dylan Corl, Keith Corrigan, Robert Cutler, William Daughton, Robert Ellis, Geoffrey Gettelfinger, Ronald Hatcher, Philip Heitzenroeder, Frank Hoffmann, Jonathan Jara-Almonte, Michael Kalish, Thomas Kozub, Enrique Merino, Weiguo Que, Benjamin Smith , et al. (31 additional authors not shown)

Abstract: The Facility for Laboratory Reconnection Experiments (FLARE) has been constructed to study magnetic reconnection in multiple X-line regimes relevant to space, astrophysical, and fusion plasmas. Building upon the successful design of the Magnetic Reconnection Experiment (MRX), FLARE features a larger physical volume, stronger magnetic fields, and an independent ohmic heating drive to significantly… ▽ More The Facility for Laboratory Reconnection Experiments (FLARE) has been constructed to study magnetic reconnection in multiple X-line regimes relevant to space, astrophysical, and fusion plasmas. Building upon the successful design of the Magnetic Reconnection Experiment (MRX), FLARE features a larger physical volume, stronger magnetic fields, and an independent ohmic heating drive to significantly extend the accessible parameter space, targeting Lundquist numbers up to S ~ 10^5 and normalized system sizes up to λ~ 10^3. This paper details the facility's core engineering components, including the primary vacuum vessel, internal flux cores, highly segmented external coil systems, modular capacitor banks, and the safety interlock and control architecture. An initial diagnostic suite is presented, comprising high-resolution 2D magnetic probe arrays, triple Langmuir probes, a fully fiber-coupled interferometer, ion Doppler spectroscopy, and fast camera imaging. Initial operations demonstrate the device's experimental flexibility and reliability, successfully executing symmetric push-pull reconnection, spheromak merging, and asymmetric downstream configurations. Currently operating within "Stage 2.5" with S ~ 2,500 and λ~ 60 for anti-parallel reconnection, FLARE provides immediate access to the multiple X-line regimes. Planned hardware upgrades, advanced diagnostic additions, and integration with fully kinetic simulations will further expand its capabilities as it transitions into a collaborative user facility for the broader plasma science community. △ Less

Submitted 17 August, 2026; originally announced August 2026.

Comments: 47 pages, 25 figures, 7 tables

EFT-Ramses: a code to simulate the effective field theory of dark energy

Authors: Nathaniel Ota Woodcock, Sownak Bose, Yunhao Gao, Baojiu Li

Abstract: While the standard $Λ$CDM paradigm is in excellent agreement with most current cosmological observations, theoretical challenges surrounding the cosmological constant ($Λ$) have strongly motivated the exploration of dynamical dark energy (DE) and modified gravity (MG) models. Investigating the physical nature of the cosmic acceleration requires N-body simulations to probe the non-linear growth of… ▽ More While the standard $Λ$CDM paradigm is in excellent agreement with most current cosmological observations, theoretical challenges surrounding the cosmological constant ($Λ$) have strongly motivated the exploration of dynamical dark energy (DE) and modified gravity (MG) models. Investigating the physical nature of the cosmic acceleration requires N-body simulations to probe the non-linear growth of cosmic structure and prepare for the high-precision data from Stage-IV surveys. In this paper, we present EFT-RAMSES, a comprehensive extension of the ECOSMOG cosmological simulation code designed to explore non-linear structure formation in DE and MG scenarios. We embed the effective field theory of dark energy (EFTofDE) framework into this new numerical pipeline, utilising the $α$-basis parameterisation to provide a versatile, model-agnostic, computational engine. By consolidating diverse scalar and vector-tensor theories---including the normal and self-accelerating Dvali-Gabadadze-Porrati (DGP) models, cubic Galileons (cubic scalar Galileon (csG), cubic vector Galileon (cvG) and generalised cubic covariant Galileon (GCCG)), and generic effective field theory (EFT) parameterisation---into a single "master" Vainshtein equation, this pipeline bypasses the need for model-specific solvers and easily specialises to any particular model. As validations, we perform high-resolution N-body simulations for the normal-branch DGP (nDGP), csG, GCCG, and EFT models, comparing the resulting matter power spectra against dependent and independent codes such as legacy ECOSMOG and HiCOLA, as well as linear theory, and find excellent agreement. EFT-RAMSES provides a robust and versatile computational tool for precision cosmological tests of DE and MG using upcoming cosmological surveys. The code is available for download from the GitHub EFT-RAMSES repository. △ Less

Submitted 27 July, 2026; originally announced July 2026.

Comments: 18 pages, 5 figures (2 more in an Appendix), submitted to MNRAS; comments welcome

HiLiftAeroML: High-Fidelity Computational Fluid Dynamics Dataset for High-Lift Aircraft Aerodynamics

Authors: Neil Ashton, Adam Clark, Liam Heidt, Christopher Ivey, Sanjeeb Bose, Rahul Agrawal, Konrad Goc, Rishi Ranade, Corey Adams, Peter Sharpe, Sheel Nidhan, Semit Akkurt, Daniel Leibovici, Jean Kossaifi

Abstract: This paper describes the first-ever open-source high-fidelity CFD dataset of a high-lift aircraft for the purpose of AI surrogate model development. The dataset is composed of 1800 samples, arising from 180 geometry variants and 10 angles of attack for the high-lift NASA Common Research Model (CRM) geometry, used within the AIAA High-Lift Prediction Workshop series. One of the novelties of this da… ▽ More This paper describes the first-ever open-source high-fidelity CFD dataset of a high-lift aircraft for the purpose of AI surrogate model development. The dataset is composed of 1800 samples, arising from 180 geometry variants and 10 angles of attack for the high-lift NASA Common Research Model (CRM) geometry, used within the AIAA High-Lift Prediction Workshop series. One of the novelties of this dataset is the use of a GPU-accelerated high-fidelity explicit, wall-modeled LES approach for each simulation, using solution-adapted grids between 300M and 500M cells. This ensures the greatest possible accuracy given known challenges in steady-state RANS approaches for these portions of the flight envelope. The entire dataset (geometries, time-averaged volume and surface variables and integral forces) are available, free of charge with a permissive open-source license (CC-BY-4.0). By making this data publicly available, we aim to accelerate the research and development of AI surrogate modeling within the aerospace industry. △ Less

Submitted 19 May, 2026; originally announced May 2026.

Role of Magnetic Field in the Redistribution of Turbulence from Large-Scale Structures to Small-Scale Fluctuations

Authors: Tanmay Karmakar, Rosh Roy, Lavkesh Lachhvani, Raju Daniel, Bhoomi Khodiyar, Prabal K. Chattopadhyay, Abhijit Sen, Sayak Bose

Abstract: Magnetized plasmas with equilibrium density gradients support drift-wave turbulence, which is often regulated by self-generated zonal flows. In this work, we experimentally examine the effect of increasing the magnetic field on turbulence characteristics in a linear plasma device. As the magnetic field is increased from 600 to 1000 G, zonal flow is suppressed while the mean flow increases. Spectra… ▽ More Magnetized plasmas with equilibrium density gradients support drift-wave turbulence, which is often regulated by self-generated zonal flows. In this work, we experimentally examine the effect of increasing the magnetic field on turbulence characteristics in a linear plasma device. As the magnetic field is increased from 600 to 1000 G, zonal flow is suppressed while the mean flow increases. Spectral analysis of density and potential fluctuations shows a redistribution of power from low-frequency (0.1-1 kHz) to high-frequency (1-300 kHz) components, along with an increase in the spectral slope and the ratio PHF/PLF. This change is linked to a reduction in Reynolds stress due to the loss of correlation between radial and poloidal velocity fluctuations, which possibly weakens the drive for zonal flow generation. Similar behavior is observed near the peak gradient region, also indicating its global nature. The present results suggest a transition from a zonal-flow-dominated regime to a state dominated by smaller-scale fluctuations, possibly influenced by mean flow shear. These findings highlight how the magnetic field redistributes spectral energy across frequency scales in drift-wave turbulent plasmas △ Less

Submitted 17 May, 2026; originally announced May 2026.

LES of Droplet Impingement: Application to Clean and Laser-Scanned Ice Shapes

Authors: Federico Zabaleta, Brett Bornhoft, Suhas S. Jain, Sanjeeb T. Bose, Parviz Moin

Abstract: The prediction of aircraft icing is conventionally performed using multishot simulation frameworks that fail to predict the progressive roughening of the ice surface. To understand roughness formation, we investigate droplet impingement on clean and laser-scanned rough ice shapes using a high-fidelity computational framework based on wall-modeled large-eddy simulations and Lagrangian particle trac… ▽ More The prediction of aircraft icing is conventionally performed using multishot simulation frameworks that fail to predict the progressive roughening of the ice surface. To understand roughness formation, we investigate droplet impingement on clean and laser-scanned rough ice shapes using a high-fidelity computational framework based on wall-modeled large-eddy simulations and Lagrangian particle tracking. This methodology is validated against experimental data for a NACA 23012 airfoil and a NACA 64A008 swept tail, accurately predicting collection efficiency and supercooled large droplet splashing. The framework is subsequently applied to laser-scanned rime ice geometries to quantify the impact of surface roughness on local impingement distributions. The results reveal that physical roughness induces a highly nonuniform collection efficiency, with droplet impingement intensely concentrated on upstream-faces of roughness elements, creating sheltered shadow zones immediately downstream. While the spanwise-averaged collection efficiency remains remarkably similar to that of an equivalent smooth body, idealized smooth surfaces completely suppress these localized impingement peaks. Ice accretion simulations demonstrate that this localized impingement creates a self-reinforcing feedback loop, actively amplifying existing roughness features over time. These findings provide a direct physical explanation for the formation of characteristic rime ice structures and highlight the critical role of local surface topology in the accretion process. △ Less

Submitted 6 May, 2026; originally announced May 2026.

Transition from Zonal Flows to Streamer like structures and associated edge Fluctuations

Authors: Tanmay Karmakar, Rosh Roy, Lavkesh Lachhvani, Raju Daniel, Bhoomi Khodiyar, Prabal K. Chattopadhyay, Abhijit Sen, Sayak Bose

Abstract: We report experimental observations of a controlled transition from a zonal-flow (ZF) dominated regime to a coexistence regime of ZFs and streamers, and finally to a streamer-dominated state in a linear magnetized plasma column. The controlling parameter is the ion-neutral collision frequency. At low collisionality (2 x 10^-5 mbar), the plasma turbulence is dominated by coherent ZFs (600-700 Hz) t… ▽ More We report experimental observations of a controlled transition from a zonal-flow (ZF) dominated regime to a coexistence regime of ZFs and streamers, and finally to a streamer-dominated state in a linear magnetized plasma column. The controlling parameter is the ion-neutral collision frequency. At low collisionality (2 x 10^-5 mbar), the plasma turbulence is dominated by coherent ZFs (600-700 Hz) that are nonlinearly driven by drift-wave fluctuations. With increasing collisionality (5 x 10^-4 mbar), the ZF growth is reduced and streamers emerge through nonlinear coupling of neighboring drift modes mediated by a mediator mode. At high collisionality (2 x 10^-3 mbar), ZFs are strongly damped and the turbulence becomes streamer-dominated. For each of these turbulent states, the corresponding edge fluctuations transition from coherent, symmetric to intermittent, asymmetric fluctuations with enhanced low-frequency content and larger spatial scales that can result in convective transport. Our results demonstrate the possibility of selective excitation of ZFs and streamers by regulating their collisional damping and establish the ion-neutral collision frequency as an effective control knob for regulating turbulent structures and edge transport in magnetized plasmas. △ Less

Submitted 5 May, 2026; originally announced May 2026.

Experimental observation of drift acoustic cnoidal waves in a magnetized plasma

Authors: Tanmay Karmakar, Rosh Roy, Lavkesh Lachhvani, Raju Daniel, Bhoomi Khodiyar, Prabal K. Chattopadhyay, Abhijit Sen, Sayak Bose

Abstract: We report the experimental observation of highly nonlinear coherent structures in a linear magnettized plasma characterized by a strong background density gradient and significant ExB velocity shear under high ion-neutral collisionality. These structures, identified as drift acoustic waves, exhibit large normalized density fluctuations reaching amplitudes of up to ~10% and show periodic sawtooth-l… ▽ More We report the experimental observation of highly nonlinear coherent structures in a linear magnettized plasma characterized by a strong background density gradient and significant ExB velocity shear under high ion-neutral collisionality. These structures, identified as drift acoustic waves, exhibit large normalized density fluctuations reaching amplitudes of up to ~10% and show periodic sawtooth-like waveforms. These observed waveforms are well described by cnoidal functions, corresponding to stationary nonlinear wave trains. Cnoidal waves are exact solutions of the Korteweg-de Vries (KdV)-type equations, alongside the more commonly studied soliton solutions. To the best of our knowledge, this work presents the first controlled experimental observation of cnoidal wave trains in a highly collisional magnetized plasma through systematic variation of profile gradients. These findings provide important new insights into the nonlinear evolution and saturation of drift acoustic waves in inhomogeneous, sheared, and collisional magnetized plasmas. △ Less

Submitted 21 April, 2026; originally announced April 2026.

Shock wave bending around a dusty plasma void

Authors: Sachin Sharma, Rauoof Wani, Prabhakar Srivastav, Meenakshee Sharma, Sayak Bose, Sanat Tiwari, Abhijit Sen

Abstract: We report on experimental observations of the bending of a dust acoustic shock wave around a dust void region. This phenomenon occurs as a planar shock wavefront encounters a compressible obstacle in the form of a void whose size is larger than the wavelength of the wave. As they collide, the central portion of the wavefront, that is the first to touch the void, is blocked while the rest of the fr… ▽ More We report on experimental observations of the bending of a dust acoustic shock wave around a dust void region. This phenomenon occurs as a planar shock wavefront encounters a compressible obstacle in the form of a void whose size is larger than the wavelength of the wave. As they collide, the central portion of the wavefront, that is the first to touch the void, is blocked while the rest of the front continues to propagate, resulting in an inward bending of the shock wave. The bent shock wave eventually collapses, leading to the transient trapping of dust particles in the void. Subsequently, a Coulomb explosion of the trapped particles generates a bow shock. The experiments have been carried out in a DC glow discharge plasma, where the shock wave and the void are simultaneously created as self-excited modes of a three-dimensional dust cloud. The salient features of this phenomenon are reproduced in molecular dynamics simulations, which provide valuable insights into the underlying dynamics of this interaction. △ Less

Submitted 15 September, 2025; originally announced September 2025.

Comments: 10 pages, 8 figures, 2 tables

A Spin-Based Pathway to Testing the Quantum Nature of Gravity

Authors: Sougato Bose, Anupam Mazumdar, Roger Penrose, Ivette Fuentes, Marko Toroš, Ron Folman, Gerard J. Milburn, Myungshik Kim, Adrian Kent, A. T. M. Anishur Rahman, Cyril Laplane, Aaron Markowitz, Debarshi Das, Ethan Campos-Méndez, Eva Kilian, David Groswasser, Menachem Givon, Or Dobkowski, Peter Skakunenko, Maria Muretova, Yonathan Japha, Naor Levi, Omer Feldman, Damián Pitalúa-García, Jonathan M. H. Gosling , et al. (30 additional authors not shown)

Abstract: A key open problem in physics is the correct way to combine gravity (described by general relativity) with everything else (described by quantum mechanics). This problem suggests that general relativity and possibly also quantum mechanics need fundamental corrections. Most physicists expect that gravity should be quantum in character, but gravity is fundamentally different to the other forces beca… ▽ More A key open problem in physics is the correct way to combine gravity (described by general relativity) with everything else (described by quantum mechanics). This problem suggests that general relativity and possibly also quantum mechanics need fundamental corrections. Most physicists expect that gravity should be quantum in character, but gravity is fundamentally different to the other forces because it alone is described by spacetime geometry. Experiments are needed to test whether gravity, and hence space-time, is quantum or classical. We propose an experiment to test the quantum nature of gravity by checking whether gravity can entangle two micron-sized crystals. A pathway to this is to create macroscopic quantum superpositions of each crystal first using embedded spins and Stern-Gerlach forces. These crystals could be nanodiamonds containing nitrogen-vacancy (NV) centres. The spins can subsequently be measured to witness the gravitationally generated entanglement. This is based on extensive theoretical feasibility studies and experimental progress in quantum technology. The eventual experiment will require a medium-sized consortium with excellent suppression of decoherence including vibrations and gravitational noise. In this white paper, we review the progress and plans towards realizing this. While implementing these plans, we will further explore the most macroscopic superpositions that are possible, which will test theories that predict a limit to this. △ Less

Submitted 1 September, 2025; originally announced September 2025.

Comments: 18 pages, 2 figures, Submission to 2025 European Strategy for Particle Physics: see https://indico.cern.ch/event/1439855/contributions/6461673/

PRISM: A MATLAB-Based Application for Structured Probe Data Management and Visualization in Tokamak Diagnostics

Authors: Priyanka Verma, Subhojit Bose, Harshita Raj, Joydeep Ghosh

Abstract: The successful operation of tokamak experiments requires accurate documentation, tracking, and visualization of diagnostic instruments, particularly electrical probes. Traditionally, this metadata is maintained manually through handwritten logbooks or semi-digital spreadsheets, leading to inefficiencies and human errors. In response to these challenges, we present PRISM (Probe Registration and Inf… ▽ More The successful operation of tokamak experiments requires accurate documentation, tracking, and visualization of diagnostic instruments, particularly electrical probes. Traditionally, this metadata is maintained manually through handwritten logbooks or semi-digital spreadsheets, leading to inefficiencies and human errors. In response to these challenges, we present PRISM (Probe Registration and Information System for Monitoring)-a MATLAB-based application developed using App Designer. PRISM provides a graphical user interface (GUI) that facilitates structured probe registration, metadata storage, and both 2D and 3D spatial visualization in tokamak geometries. Tested with data from the ADITYA-U tokamak, PRISM helps users enter information accurately, retrieve metadata easily, and visualize probe setups. The tool is built in a flexible way, is not limited to a specific setup, and could potentially support future developments such as digital twins and real-time control systems. △ Less

Submitted 30 August, 2025; originally announced September 2025.

Report number: IPR/TR-891/2025

Radial asymmetry in quadrupole mass filters: stability, multipole fields and resolution enhancement

Authors: Sukanya Jana, Snigdha Bose, Sayel Chakraborty, Pintu Mandal, Nabanita Deb

Abstract: This study examines the effects of radial asymmetry in a linear quadrupole mass filter with circular rods, introduced either by a change in electrode radii or by displacement of a diametrically opposite pair. A radial potential model is developed to account for the resulting geometric deviations, enabling analysis of the first stability region specific to the quadrupole component. The transmission… ▽ More This study examines the effects of radial asymmetry in a linear quadrupole mass filter with circular rods, introduced either by a change in electrode radii or by displacement of a diametrically opposite pair. A radial potential model is developed to account for the resulting geometric deviations, enabling analysis of the first stability region specific to the quadrupole component. The transmission characteristics of such asymmetric configurations are systematically examined, revealing a linear shift in the transmission peak along the q-axis as a function of the asymmetry parameter. This behavior is interpreted through modifications observed in the stability diagram. Furthermore, increased asymmetry is shown to broaden the transmission contours and generally reduce resolution. Notably, a `magic' asymmetry parameter of -0.02 corresponding to electrode displacement, yields enhanced resolution compared to the symmetric case for a fixed rod-to-field radius ratio. An empirical relationship is established between the resolution and the combined contribution of the coefficients of octupole and dodecapole potential components, highlighting the critical role of higher-order field effects in performance optimization. △ Less

Submitted 28 August, 2025; originally announced August 2025.

Identification and Characterization of a New Disruption Regime in ADITYA-U Tokamak

Authors: Soumitra Banerjee, Harshita Raj, Sk Injamul Hoque, Komal Yadav, Sharvil Patel, Ankit Kumar, Kaushlender Singh, Ashok Kumawat, Bharat Hegde, Subhojit Bose, Priyanka Verma, Kumudini Tahiliani, Asha Adhiya, Manoj Kumar, Rohit Kumar, Malay Bikash Chowdhuri, Nilam Ramaiya, Ananya Kundu, Suman Aich, Suman Dolui, K. A. Jadeja, K. M. Patel, Ankit Patel, Rakesh L. Tanna, Joydeep Ghosh

Abstract: Disruptions continue to pose a significant challenge to the stable operation and future design of tokamak reactors. A comprehensive statistical investigation carried out on the ADITYA-U tokamak has led to the observation and characterization of a novel disruption regime. In contrast to the conventional Locked Mode Disruption (LMD), the newly identified disruption exhibits a distinctive two-phase e… ▽ More Disruptions continue to pose a significant challenge to the stable operation and future design of tokamak reactors. A comprehensive statistical investigation carried out on the ADITYA-U tokamak has led to the observation and characterization of a novel disruption regime. In contrast to the conventional Locked Mode Disruption (LMD), the newly identified disruption exhibits a distinctive two-phase evolution: an initial phase characterized by a steady rise in mode frequency with a nonlinearly saturated amplitude, followed by a sudden frequency collapse accompanied by a pronounced increase in amplitude. This behaviour signifies the onset of the precursor phase on a significantly shorter timescale. Clear empirical thresholds have been identified to distinguish this disruption type from conventional LMD events, including edge safety factor, current decay coefficient, current quench (CQ) time, and CQ rate. The newly identified disruption regime is predominantly governed by the (m/n = 2/1) drift-tearing mode (DTM), which, in contrast to typical disruptions in the ADITYA-U tokamak that involve both m/n = 2/1 and 3/1 modes, consistently manifests as the sole dominant instability. Initiated by core temperature hollowing, the growth of this mode is significantly enhanced by a synergistic interplay between a strongly localized pressure gradient and the pronounced steepening of the current density profile in the vicinity of the mode rational surface. △ Less

Submitted 23 July, 2025; originally announced July 2025.

Predictions of flow distortions inside a serpentine diffuser from large-eddy simulations

Authors: Rahul Agrawal, Chad Winkler, Sanjeeb Bose, Parviz Moin

Abstract: This work examines the flow separation and the resulting pressure distortions at the exit plane of a serpentine diffuser operating at both subsonic and transonic conditions. Wallmodeled large-eddy simulations (WMLES) using the charLES flow solver are performed at three exit-plane Mach numbers, Ma_AIP ~ {0.36, 0.46, 0.54}. First, it is shown that the onset of flow separation inside a serpentine dif… ▽ More This work examines the flow separation and the resulting pressure distortions at the exit plane of a serpentine diffuser operating at both subsonic and transonic conditions. Wallmodeled large-eddy simulations (WMLES) using the charLES flow solver are performed at three exit-plane Mach numbers, Ma_AIP ~ {0.36, 0.46, 0.54}. First, it is shown that the onset of flow separation inside a serpentine diffuser may likely experience strong, non-local history effects. A grid refinement study consisting of five grids (from 30 million to 3 billion cells) is conducted for all Mach numbers. The recently proposed dynamic tensor-coefficient Smagorinsky subgrid-scale and sensor-aided non-equilibrium wall models compare favorably with experimental measurements for the pressure recovery and azimuthal flow distortion at all Mach numbers. The pressure recovery and azimuthal flow distortion are predicted to within 0.3% and 7%, respectively, which are both within the experimental error bounds. However, the simulations underpredict the maximum azimuthal distortion in comparison to the experiments for all conditions. Statistical comparisons of the dynamic azimuthal flow distortions suggest that the present LES reasonably captures the ring-averaged mean distortions, and the statistical distributions of the distortion around the mean. Extreme events are underestimated by the present simulations, potentially highlighting that significantly longer integration times may be necessary. △ Less

Submitted 18 June, 2025; originally announced June 2025.

Comments: Under submission for publication consideration in AIAA-J. 29 pages, 29 figures

Large eddy simulations of conjugate heat transfer in boundary layers over laser-scanned ice roughness

Authors: Federico Zabaleta, Brett Bornhoft, Suhas S. Jain, Sanjeeb T. Bose, Parviz Moin

Abstract: Accurate modeling of ice accretion is important for safe and efficient design of aircraft and wind turbine systems. Heat transfer predictions obtained from fluid flow solvers are used as input in ice accretion codes. In glaze ice conditions, freezing rates and resulting ice shapes are highly sensitive to input values of the heat transfer coefficient. Hence, accurate prediction of heat transfer on… ▽ More Accurate modeling of ice accretion is important for safe and efficient design of aircraft and wind turbine systems. Heat transfer predictions obtained from fluid flow solvers are used as input in ice accretion codes. In glaze ice conditions, freezing rates and resulting ice shapes are highly sensitive to input values of the heat transfer coefficient. Hence, accurate prediction of heat transfer on iced airfoils is crucial for correctly predicting the ice accretion process. In this study, we perform conjugate heat transfer (CHT) simulations using wall-modeled large-eddy simulation (WMLES) over surfaces characterized by ice roughness. The results show that WMLES with CHT accurately captures surface temperature distributions and heat fluxes across a range of roughness geometries. For cases considered, large roughness-to-boundary-layer thickness ratios disrupt outer-layer similarity, leading to substantial errors in estimating equivalent sandgrain roughness when applying traditional empirical models based on surface statistics. The simulations further show that local heat fluxes vary significantly across roughness elements due to low thermal conductivity of the solid; in particular, roughness crests exhibit reduced fluxes in contrast to slopes and valleys. Notably, as roughness height increases, wall heat flux at the crest diminishes, even leading to heat flux reversal in some cases, where thermal energy is transferred from fluid to solid. These effects are not captured in isothermal wall simulations, which overestimate the Stanton number, especially at roughness peaks. By enabling calculation of Stanton number using heat flux distributions, not directly available in experiments, the present simulations augment experimental results and highlight the importance of including solid conduction effects for accurately modeling heat transfer over rough, low-conductivity surfaces such as ice. △ Less

Submitted 23 September, 2025; v1 submitted 9 June, 2025; originally announced June 2025.

Effects of lower floating-point precision on scale-resolving numerical simulations of turbulence

Authors: Martin Karp, Ronith Stanly, Timofey Mukha, Luca Galimberti, Siavash Toosi, Hang Song, Lissandro Dalcin, Saleh Rezaeiravesh, Niclas Jansson, Stefano Markidis, Matteo Parsani, Sanjeeb Bose, Sanjiva Lele, Philipp Schlatter

Abstract: Modern computing clusters offer specialized hardware for reduced-precision arithmetic that can speed up the time to solution significantly. This is possible due to a decrease in data movement, as well as the ability to perform arithmetic operations at a faster rate. However, for high-fidelity simulations of turbulence, such as direct and large-eddy simulation, the impact of reduced precision on th… ▽ More Modern computing clusters offer specialized hardware for reduced-precision arithmetic that can speed up the time to solution significantly. This is possible due to a decrease in data movement, as well as the ability to perform arithmetic operations at a faster rate. However, for high-fidelity simulations of turbulence, such as direct and large-eddy simulation, the impact of reduced precision on the computed solution and the resulting uncertainty across flow solvers and different flow cases have not been explored in detail and limits the optimal utilization of new high-performance computing systems. In this work, the effect of reduced precision is studied using four diverse computational fluid dynamics (CFD) solvers (two incompressible, Neko and Simson, and two compressible, PadeLibs and SSDC) using four test cases: turbulent channel flow at Retau = 550 and higher, forced transition in a channel, flow over a cylinder at ReD = 3900, and compressible flow over a wing section at Rec = 50000. We observe that the flow physics are remarkably robust with respect to reduction in lower floating-point precision, and that often other forms of uncertainty, due to for example time averaging, often have a much larger impact on the computed result. Our results indicate that different terms in the Navier-Stokes equations can be computed to a lower floating-point accuracy without affecting the results. In particular, standard IEEE single precision can be used effectively for the entirety of the simulation, showing no significant discrepancies from double-precision results across the solvers and cases considered. Potential pitfalls are also discussed. △ Less

Submitted 15 December, 2025; v1 submitted 5 June, 2025; originally announced June 2025.

The CHIMERAS Project: Design Framework for the Collisionless HIgh-beta Magnetized Experiment Researching Astrophysical Systems

Authors: S. Dorfman, S. Bose, E. Lichko, M. Abler, J. Juno, J. M. TenBarge, Y. Zhang, S. Chakraborty Thakur, C. A. Cartagena-Sanchez, P. Tatum, E. Scime, G. Joshi, S. Greess, C. Kuchta

Abstract: From the near-Earth solar wind to the intracluster medium of galaxy clusters, collisionless, high-beta, magnetized plasmas pervade our universe. Energy and momentum transport from large-scale fields and flows to small scale motions of plasma particles is ubiquitous in these systems, but a full picture of the underlying physical mechanisms remains elusive. The transfer is often mediated by a turbul… ▽ More From the near-Earth solar wind to the intracluster medium of galaxy clusters, collisionless, high-beta, magnetized plasmas pervade our universe. Energy and momentum transport from large-scale fields and flows to small scale motions of plasma particles is ubiquitous in these systems, but a full picture of the underlying physical mechanisms remains elusive. The transfer is often mediated by a turbulent cascade of Alfv{é}nic fluctuations as well as a variety of kinetic instabilities; these processes tend to be multi-scale and/or multi-dimensional, which makes them difficult to study using spacecraft missions and numerical simulations alone (Dorfman et al. 2023; Lichko et al. 2020, 2023). Meanwhile, existing laboratory devices struggle to produce the collisionless, high ion beta ($β_i \gtrsim 1$), magnetized plasmas across the range of scales necessary to address these problems. As envisioned in recent community planning documents (Carter et al. 2020; Milchberg and Scime 2020; Baalrud et al. 2020; Dorfman et al. 2023; National Academies of Sciences, Engineering, and Medicine 2024, it is therefore important to build a next generation laboratory facility to create a $β_i \gtrsim 1$, collisionless, magnetized plasma in the laboratory for the first time. A Working Group has been formed and is actively defining the necessary technical requirements to move the facility towards a construction-ready state. Recent progress includes the development of target parameters and diagnostic requirements as well as the identification of a need for source-target device geometry. As the working group is already leading to new synergies across the community, we anticipate a broad community of users funded by a variety of federal agencies (including NASA, DOE, and NSF) to make copious use of the future facility. △ Less

Submitted 9 May, 2025; originally announced May 2025.

Comments: 18 pages, 1 figure

Measurement of energy reduction by inertial Alfvén waves propagating through parallel gradients in the Alfvén speed

Authors: Garima Joshi, Sayak Bose, Troy Carter, Daniel Wolf Savin, Shreekrishna Tripathi, Stephen Vincena, Michael Hahn

Abstract: We have studied the propagation of inertial Alfvén waves through parallel gradients in the Alfvén speed using the Large Plasma Device at the University of California, Los Angeles. The reflection and transmission of Alfvén waves through inhomogeneities in the background plasma is important for understanding wave propagation, turbulence, and heating in space, laboratory, and astrophysical plasmas. H… ▽ More We have studied the propagation of inertial Alfvén waves through parallel gradients in the Alfvén speed using the Large Plasma Device at the University of California, Los Angeles. The reflection and transmission of Alfvén waves through inhomogeneities in the background plasma is important for understanding wave propagation, turbulence, and heating in space, laboratory, and astrophysical plasmas. Here we \rev{present inertial Alfvén waves, under conditions relevant to solar flares and the solar corona. We find} that the transmission of the inertial Alfvén waves is reduced as the sharpness of the gradient is increased. Any reflected waves were below the detection limit of our experiment and reflection cannot account for all of the energy not transmitted through the gradient. Our findings indicate that, for both kinetic and inertial Alfvén waves, the controlling parameter for the transmission of the waves through an Alfvén speed gradient is the ratio of the Alfvén wavelength along the gradient divided by the scale length of the gradient. Furthermore, our results suggest that an as-yet-unidentified damping process occurs in the gradient. △ Less

Submitted 24 February, 2025; originally announced February 2025.

Sharing quantum nonlocality and teleportation over long distance using optical hybrid states

Authors: Subhankar Bera, Soumyakanti Bose, Hyunseok Jeong, Archan S Majumdar

Abstract: We analyze sharing Bell-type nonlocal correlation between two distant parties with optical hybrid states comprising a single photon polarization state and a multiphoton coherent state. By deploying entanglement swapping over the coherent state parts at the middle station, we show that the optical hybrid states can efficiently generate a polarization-entangled state that violates Clauser-Horne-Shim… ▽ More We analyze sharing Bell-type nonlocal correlation between two distant parties with optical hybrid states comprising a single photon polarization state and a multiphoton coherent state. By deploying entanglement swapping over the coherent state parts at the middle station, we show that the optical hybrid states can efficiently generate a polarization-entangled state that violates Clauser-Horne-Shimony-Holt (CHSH) Bell-inequality well over a metropolitan distance. We further assess the quality of the shared entangled state in the information processing task of quantum teleportation of an unknown polarization qubit. Our results with realistic devices, embedding detection inefficiency and transmission losses, indicate the viability of faithful quantum teleportation over large distances, consistent with the quality of the shared correlation. △ Less

Submitted 30 September, 2025; v1 submitted 2 February, 2025; originally announced February 2025.

Comments: 15 pages, 6 Figures

Observation of Kolmogorov turbulence due to multiscale vortices in dusty plasma experiments

Authors: Sachin Sharma, Rauoof Wani, Prabhakar Srivastav, Meenakshee Sharma, Sayak Bose, Yogesh Saxena, Sanat Tiwari

Abstract: We report the experimental observation of fully developed Kolmogorov turbulence originating from self-excited vortex flows in a three-dimensional (3D) dust cloud. The characteristic -5/3 scaling of three-dimensional Kolmogorov turbulence is universally observed in both the spatial and temporal power spectra. Additionally, the 2/3 scaling in the second-order structure function further confirms the… ▽ More We report the experimental observation of fully developed Kolmogorov turbulence originating from self-excited vortex flows in a three-dimensional (3D) dust cloud. The characteristic -5/3 scaling of three-dimensional Kolmogorov turbulence is universally observed in both the spatial and temporal power spectra. Additionally, the 2/3 scaling in the second-order structure function further confirms the presence of Kolmogorov turbulence. We also identified a slight deviation in the tails of the probability distribution functions for velocity gradients. The dust cloud formed in the diffused region away from the electrode and above the glass device surface in the glow discharge experiments. The dust rotation was observed in multiple experimental campaigns under different discharge conditions at different spatial locations and background plasma environments. △ Less

Submitted 29 October, 2024; v1 submitted 10 August, 2024; originally announced August 2024.

Comments: 13 pages, 14 figures

Non-equilibrium wall model for large eddy simulations of complex flows exhibiting turbulent smooth body separation

Authors: Rahul Agrawal, Sanjeeb T. Bose, Parviz Moin

Abstract: In this work, a non-equilibrium wall model is proposed for the prediction of turbulent flows experiencing adverse pressure gradients, including separated flow regimes. The mean-flow nonequilibrium is identified by comparing two characteristic velocities: the friction velocity (u_tau) and the viscous-pressure gradient velocity (up). In regions where the pressure gradient velocity is comparable to t… ▽ More In this work, a non-equilibrium wall model is proposed for the prediction of turbulent flows experiencing adverse pressure gradients, including separated flow regimes. The mean-flow nonequilibrium is identified by comparing two characteristic velocities: the friction velocity (u_tau) and the viscous-pressure gradient velocity (up). In regions where the pressure gradient velocity is comparable to the friction velocity (up \sim u_tau, the near-wall turbulent closure is modified to include the effect of the pressure-gradient and convective terms. The performance of this wall model is evaluated in two canonical flows experiencing smooth body separation: the NASA-Boeing speed bump and the Bachalo-Johnson bump. Improvements in the predictive capabilities of the proposed model for the conventional equilibrium wall model are theorized and then demonstrated through numerical experiments. In particular, the proposed wall model can capture the onset of boundary layer separation observed in experiments or DNS calculations at resolutions where the equilibrium wall model fails to separate. △ Less

Submitted 16 July, 2024; originally announced July 2024.

Comments: Under review for publication in Physical Review Fluids. 20 pages, 14 figures

The Solar eruptioN Integral Field Spectrograph

Authors: Vicki L. Herde, Phillip C. Chamberlin, Don Schmit, Adrian Daw, Ryan O. Milligan, Vanessa Polito, Souvik Bose, Spencer Boyajian, Paris Buedel, Will Edgar, Alex Gebben, Qian Gong, Ross Jacobsen, Nicholas Nell, Bennet Schwab, Alan Sims, David Summers, Zachary Turner, Trace Valade, Joseph Wallace

Abstract: The Solar eruptioN Integral Field Spectrograph (SNIFS) is a solar-gazing spectrograph scheduled to fly in the summer of 2025 on a NASA sounding rocket. Its goal is to view the solar chromosphere and transition region at a high cadence (1s) both spatially (0.5") and spectrally (33 mÅ) viewing wavelengths around Lyman Alpha (1216 Å), Si iii (1206 Å) and O v (1218 Å) to observe spicules, nanoflares,… ▽ More The Solar eruptioN Integral Field Spectrograph (SNIFS) is a solar-gazing spectrograph scheduled to fly in the summer of 2025 on a NASA sounding rocket. Its goal is to view the solar chromosphere and transition region at a high cadence (1s) both spatially (0.5") and spectrally (33 mÅ) viewing wavelengths around Lyman Alpha (1216 Å), Si iii (1206 Å) and O v (1218 Å) to observe spicules, nanoflares, and possibly a solar flare. This time cadence will provide yet-unobserved detail about fast-changing features of the Sun. The instrument is comprised of a Gregorian-style reflecting telescope combined with a spectrograph via a specialized mirrorlet array that focuses the light from each spatial location in the image so that it may be spectrally dispersed without overlap from neighboring locations. This paper discusses the driving science, detailed instrument and subsystem design, and pre-integration testing of the SNIFS instrument. △ Less

Submitted 11 July, 2024; originally announced July 2024.

Comments: 22 pages (not including references), 7 figures, submitting to Solar Physics

Studies of Transonic Aircraft Flows and Prediction of Initial Buffet Onset Using Large-Eddy Simulations

Authors: Konrad A. Goc, Rahul Agrawal, Sanjeeb T. Bose, Parviz Moin

Abstract: This article utilizes the Large-Eddy Simulation (LES) paradigm with a physics-based turbulence modeling approach, including a dynamic subgrid-scale model and an equilibrium wall model, to examine the flow over the NASA transonic Common Research Model (CRM), a flow configuration that has been the focus of several AIAA Drag PredictionWorkshops (DPWs). The current work explores sensitivities to lamin… ▽ More This article utilizes the Large-Eddy Simulation (LES) paradigm with a physics-based turbulence modeling approach, including a dynamic subgrid-scale model and an equilibrium wall model, to examine the flow over the NASA transonic Common Research Model (CRM), a flow configuration that has been the focus of several AIAA Drag PredictionWorkshops (DPWs). The current work explores sensitivities to laminar-to-turbulent transition, wind tunnel mounting system, grid resolution, and grid topology and suggests current best practices in the context of large-eddy simulations of transonic aircraft flows. It is found that promoting the flow transition to turbulence via an array of cylindrical trip dots, including the sting mounting system in the simulations, and leveraging stranded boundary layer grids all tend to improve the quality of the LES solutions. Non-monotonic grid convergence in the LES calculations is observed to be strongly sensitive to grid topology, and stranded meshes rectify this issue relative to their hexagonal close-packed (HCP) counterparts. The details of the boundary layer profiles both at the leading edge of the wing and within the shock-induced separation bubble are studied, with thicknesses and integral measures reported, providing details about the boundary layer characteristics to turbulence modelers not typically available from complex aircraft flows. Finally, an assessment of the initial buffet prediction capabilities of LES is made in the context of a simpler NACA 0012 flow, with computational predictions showing reasonable agreement with available experimental data for the angle of attack at initial buffet onset and shock oscillation frequency associated with sustained buffet. △ Less

Submitted 9 July, 2024; originally announced July 2024.

Comments: Under review for publication consideration in the Journal of Aircraft

The sPHENIX Micromegas Outer Tracker

Authors: S. Aune, B. Azmoun, A. Bonenfant, S. Boose, M. Bregant, D. Cacace, R. W. da Silva, R. Feder, A. Francisco, C. Goblin, A. Grabas, J. S. Haggerty, R. A. Hernandez, H. D. H. Herrera, J. Huang, J. Kelsey, I. Kotov, J. Kuczewski, I. Mandjavidze, T. A. Martins, J. Mead, J. Mills, A. Oskarsson, H. Pereira Da Costa, C. Pinkenburg , et al. (15 additional authors not shown)

Abstract: The sPHENIX Time Projection Chamber Outer Tracker (TPOT) is a Micromegas based detector. It is a part of the sPHENIX experiment that aims to facilitate the calibration of the Time Projection Chamber, in particular the correction of the time-averaged and beam-induced distortions of the electron drift. This paper describes the detector mission, setup, construction, installation, commissioning and pe… ▽ More The sPHENIX Time Projection Chamber Outer Tracker (TPOT) is a Micromegas based detector. It is a part of the sPHENIX experiment that aims to facilitate the calibration of the Time Projection Chamber, in particular the correction of the time-averaged and beam-induced distortions of the electron drift. This paper describes the detector mission, setup, construction, installation, commissioning and performance during the first year of sPHENIX data taking. △ Less

Submitted 26 July, 2024; v1 submitted 20 March, 2024; originally announced March 2024.

Comments: 35 pages, 36 figures

Journal ref: Nuclear Instruments and Methods in Physics Research A 1066 (2024) 169615

Elastic interactions compete with persistent cell motility to drive durotaxis

Authors: Subhaya Bose, Haiqin Wang, Xinpeng Xu, Arvind Gopinath, Kinjal Dasbiswas

Abstract: The directed migration of cells toward stiffer substrate regions or durotaxis is relevant to tissue development and tumor progression. Here, we introduce a phenomenological model for single cell durotaxis that incorporates both elastic deformation-mediated cell-substrate interactions and the stochasticity of cell migration. Our model is motivated by a key observation in an early demonstration of d… ▽ More The directed migration of cells toward stiffer substrate regions or durotaxis is relevant to tissue development and tumor progression. Here, we introduce a phenomenological model for single cell durotaxis that incorporates both elastic deformation-mediated cell-substrate interactions and the stochasticity of cell migration. Our model is motivated by a key observation in an early demonstration of durotaxis: a single, contractile cell at a sharp interface between a softer and a stiffer region of an elastic substrate reorients and migrates towards the stiffer region. We model migrating cells as self-propelling, persistently motile agents that exert contractile traction forces on their elastic substrate. The resulting substrate deformations induce elastic interactions with mechanical boundaries, captured by an elastic potential. Cell dynamics are governed by two critical parameters: the strength of the traction-induced boundary interaction (A) and the persistence of cell motility (Pe). The resulting elastic forces and torques align cells perpendicular (parallel) to the boundary and accumulate (deplete) them at clamped (free) boundaries. A clamped boundary induces an attractive potential, promoting durotaxis, while a free boundary generates a repulsive potential, preventing anti-durotaxis. By analyzing steady-state position and orientation probabilities, we show how accumulation and depletion depend on elastic potential strength and motility. We compare our findings with biological microswimmers and other active particles that accumulate at confining boundaries. The model defines metrics for boundary accumulation and durotaxis, presenting a phase diagram with three regimes: durotaxis, adurotaxis, and motility-induced accumulation. Our model predicts how durotaxis depends on cell contractility and motility, offering insights and testable predictions for future experiments. △ Less

Submitted 22 December, 2024; v1 submitted 22 February, 2024; originally announced February 2024.

Comments: 11 figures, 24 pages

Journal ref: Biophys.J. 123 (2024), 21, 3721 - 3735

Experimental study of Alfvén wave reflection from an Alfvén-speed gradient relevant to the solar coronal holes

Authors: Sayak Bose, Jason M. TenBarge, Troy Carter, Michael Hahn, Hantao Ji, James Juno, Daniel Wolf Savin, Shreekrishna Tripathi, Stephen Vincena

Abstract: We report the first experimental detection of a reflected Alfvén wave from an Alfvén-speed gradient under conditions similar to those in coronal holes. The experiments were conducted in the Large Plasma Device at the University of California, Los Angeles. We present the experimentally measured dependence of the coefficient of reflection versus the wave inhomogeneity parameter, i.e., the ratio of t… ▽ More We report the first experimental detection of a reflected Alfvén wave from an Alfvén-speed gradient under conditions similar to those in coronal holes. The experiments were conducted in the Large Plasma Device at the University of California, Los Angeles. We present the experimentally measured dependence of the coefficient of reflection versus the wave inhomogeneity parameter, i.e., the ratio of the wave length of the incident wave to the length scale of the gradient. Two-fluid simulations using the Gkeyll code qualitatively agree with and support the experimental findings. Our experimental results support models of wave heating that rely on wave reflection at low heights from a smooth Alfvén-speed gradient to drive turbulence. △ Less

Submitted 9 February, 2024; originally announced February 2024.

Dark Matter Searches with Levitated Sensors

Authors: Eva Kilian, Markus Rademacher, Jonathan M. H. Gosling, Julian H. Iacoponi, Fiona Alder, Marko Toroš, Antonio Pontin, Chamkaur Ghag, Sougato Bose, Tania S. Monteiro, P. F. Barker

Abstract: Motivated by the current interest in employing quantum sensors on Earth and in space to conduct searches for new physics, we provide a perspective on the suitability of large-mass levitated optomechanical systems for observing dark matter signatures. We discuss conservative approaches of recoil detection through spectral analysis of coherently scattered light, enhancements of directional effects d… ▽ More Motivated by the current interest in employing quantum sensors on Earth and in space to conduct searches for new physics, we provide a perspective on the suitability of large-mass levitated optomechanical systems for observing dark matter signatures. We discuss conservative approaches of recoil detection through spectral analysis of coherently scattered light, enhancements of directional effects due to cross-correlation spectral densities, and the possibility of using quantum superpositions of mesoscopic test particles to measure rare events. △ Less

Submitted 31 January, 2024; originally announced January 2024.

Comments: 12 pages, 6 figures, 1 table

Journal ref: AVS Quantum Sci. 6, 030503 (2024)

Identifying noise transients in gravitational-wave data arising from nonlinear couplings

Authors: Bernard Hall, Sudhagar Suyamprakasam, Nairwita Mazumder, Anupreeta More, Sukanta Bose

Abstract: Noise in various interferometer systems can sometimes couple non-linearly to create excess noise in the gravitational wave (GW) strain data. Third-order statistics, such as bicoherence and biphase, can identify these couplings and help discriminate those occurrences from astrophysical GW signals. However, the conventional analysis can yield large bicoherence values even when no phase-coupling is p… ▽ More Noise in various interferometer systems can sometimes couple non-linearly to create excess noise in the gravitational wave (GW) strain data. Third-order statistics, such as bicoherence and biphase, can identify these couplings and help discriminate those occurrences from astrophysical GW signals. However, the conventional analysis can yield large bicoherence values even when no phase-coupling is present, thereby, resulting in false identifications. Introducing artificial phase randomization in computing the bicoherence reduces such occurrences with negligible impact on its effectiveness for detecting true phase-coupled disturbances. We demonstrate this property with simulated disturbances in this work. Statistical hypothesis testing is used for distinguishing phase-coupled disturbances from non-phase coupled ones when employing the phase-randomized bicoherence. We also obtain an expression for the bicoherence value that minimizes the sum of the probabilities of false positives and false negatives. This can be chosen as a threshold for shortlisting bicoherence triggers for further scrutiny for the presence of non-linear coupling. Finally, the utility of the phase-randomized bicoherence analysis in GW time-series data is demonstrated for the following three scenarios: (1) Finding third-order statistical similarities within categories of noise transients, such as blips and koi fish. If these non-Gaussian noise transients, or glitches, have a common source, their bicoherence maps can have similarities arising from common bifrequencies related to that source. (2) Differentiating linear or non-linear phase-coupled glitches from compact binary coalescence signals through their bicoherence maps. This is explained with a simulated signal. (3) Identifying repeated bifrequencies in the second and third observation runs (i.e., O2 and O3) of LIGO and Virgo. △ Less

Submitted 25 July, 2024; v1 submitted 30 January, 2024; originally announced January 2024.

Comments: 25 Pages, 10 figures. Reviewed by LIGO Scientific Collaboration (LSC) with LIGO Document Number P2200344

Reynolds number dependence of length scales governing turbulent flow separation with application to wall-modeled large-eddy simulations

Authors: Rahul Agrawal, Sanjeeb Bose, Parviz Moin

Abstract: This article proposes a Reynolds number scaling of the required grid points to perform wall-modeled LES of turbulent flows encountering separation off a solid surface. Based on comparisons between the various time scales in a non-equilibrium (due to the action of an external pressure gradient) turbulent boundary layer, a simple definition of the near-wall ``under-equilibrium" and ``out-of-equilibr… ▽ More This article proposes a Reynolds number scaling of the required grid points to perform wall-modeled LES of turbulent flows encountering separation off a solid surface. Based on comparisons between the various time scales in a non-equilibrium (due to the action of an external pressure gradient) turbulent boundary layer, a simple definition of the near-wall ``under-equilibrium" and ``out-of-equilibrium" scales is put forward (where ``under-equilibrium" refers to scales governed by a quasi-balance between the viscous and the pressure gradient terms). It is shown that the former length scale varies with Reynolds number as lp Re^(-2/3). The same scaling is obtained from a simplified Green's function solution of the Poisson equation in the vicinity of the separation point. A-priori analysis demonstrates that the resolution required to reasonably predict the wall-shear stress (for example, errors lower than approximately 10-15% in the entire domain) in several nonequilibrium flows is at least O(10) lp irrespective of the Reynolds number and the Clauser parameter. Further, a series of a-posteriori validation studies are performed to determine the accuracy of this scaling including the flow over the Boeing speed bump, Song-Eaton diffuser, Notre-Dame Ramp, and the backward-facing step. The results suggest that for these flows, scaling the computational grids () such that / lp is independent of the Reynolds number results in accurate predictions of flow separation at the same ``nominal" grid resolution across different Reynolds numbers. Finally, it is suggested that in the vicinity of the separation and reattachment points, the grid-point requirements for wall-modeled large eddy simulations may scale as Re^4/3, which is more restrictive than the previously proposed flat-plate boundary layer-based estimates (Re1) of Choi and Moin (Phys. Fluids, 2012) and Yang and Griffin (Phys. Fluids, 2021). △ Less

Submitted 29 December, 2023; originally announced January 2024.

Comments: 21 pages, 17 figures. Submitted to AIAA Journal for publication consideration

Full-magnetic implementation of a classical Toffoli gate

Authors: Davide Nuzzi, Leonardo Banchi, Ruggero Vaia, Enrico Compagno, Alessandro Cuccoli, Paola Verrucchi, Sougato Bose

Abstract: The Toffoli gate is the essential ingredient for reversible computing, an energy efficient classical computational paradigm that evades the energy dissipation resulting from Landauer's principle. In this paper we analyze different setups to realize a magnetic implementation of the Toffoli gate using three interacting classical spins, each one embodying one of the three bits needed for the Toffoli… ▽ More The Toffoli gate is the essential ingredient for reversible computing, an energy efficient classical computational paradigm that evades the energy dissipation resulting from Landauer's principle. In this paper we analyze different setups to realize a magnetic implementation of the Toffoli gate using three interacting classical spins, each one embodying one of the three bits needed for the Toffoli gate. In our scheme, different control-spins configurations produce an effective field capable of conditionally flipping the target spin. We study what are the experimental requirements for the realization of our scheme, focusing on the degree of local control, the ability to dynamically switch the spin-spin interactions, and the required single-spin anisotropies to make the classical spin stable, showing that these are compatible with current technology. △ Less

Submitted 4 March, 2024; v1 submitted 26 October, 2023; originally announced October 2023.

An extension of Thwaites method for turbulent boundary layers

Authors: Rahul Agrawal, Sanjeeb T. Bose, Kevin P. Griffin, Parviz Moin

Abstract: Thwaites (1949) developed an approximate method for determining the evolution of laminar boundary layers. The approximation follows from an assumption that the growth of a laminar boundary layer in the presence of pressure gradients could be parameterized solely as a function of a flow parameter, $m = θ^2/ν\frac{dU_e}{ds}$, thus reducing the von Karman momentum integral to a first-order ordinary d… ▽ More Thwaites (1949) developed an approximate method for determining the evolution of laminar boundary layers. The approximation follows from an assumption that the growth of a laminar boundary layer in the presence of pressure gradients could be parameterized solely as a function of a flow parameter, $m = θ^2/ν\frac{dU_e}{ds}$, thus reducing the von Karman momentum integral to a first-order ordinary differential equation. This method is useful for the analysis of laminar flows, and in computational potential flow solvers to account for the viscous effects. However, for turbulent flows, a similar approximation for turbulent boundary layers subjected to pressure gradients does not yet exist. In this work, an approximate method for determining the momentum thickness of a two-dimensional, turbulent boundary layer is proposed. It is shown that the method provides good estimates of the momentum thickness, when compared to available high-fidelity simulation data, for multiple boundary layers including both favorable and adverse pressure gradient effects, up to the point of separation. In the limit of high Reynolds numbers, it is possible to derive a criterion for the onset of separation from the proposed model which is shown to be in agreement with prior empirical observations (Alber, \textit{$9^{th}$ Aerospace Sciences Meeting, 1971}). The sensitivity of the separation location with respect to upstream perturbations is also analyzed through this model for the NASA/Boeing speed bump and the transonic Bachalo-Johnson bump △ Less

Submitted 24 October, 2023; originally announced October 2023.

Comments: 21 pages, 13 figures. Under consideration for publication in J. Fluid Mech

Large-eddy simulations of the NACA23012 airfoil with laser-scanned ice shapes

Authors: Brett Bornhoft, Suhas S. Jain, Konrad Goc, Sanjeeb T. Bose, Parviz Moin

Abstract: In this study, five ice shapes generated at NASA Glenn's Icing Research Tunnel (IRT) are simulated at multiple angles of attack (Broeren et al., J. of Aircraft, 2018). These geometries target different icing environments, both early-time and longer-duration glaze and rime ice exposure events, including a geometry that results from using a thermal ice-protection system. Using the laser-scanned geom… ▽ More In this study, five ice shapes generated at NASA Glenn's Icing Research Tunnel (IRT) are simulated at multiple angles of attack (Broeren et al., J. of Aircraft, 2018). These geometries target different icing environments, both early-time and longer-duration glaze and rime ice exposure events, including a geometry that results from using a thermal ice-protection system. Using the laser-scanned geometries, detailed representations of the three-dimensional ice geometries are resolved on the grid and simulated using wall-modeled LES. Integrated loads (lift, drag, and moment coefficients) and pressure distributions are compared against experimental measurements in both clean and iced conditions for several angles of attack in both pre-and post-stall regions. The relevant comparisons to the experimental results show that qualitative and acceptable quantitative agreement with the data is observed across all geometries. Glaze ice formations exhibit larger and highly nonuniform ice features, such as `horns', in contrast to rime ice formations characterized by smaller, uniformly distributed roughness elements. In wall-modeled LES, it was observed that larger roughness scales in the glaze ice that trigger transition can be accurately resolved. Therefore, it is possible for WMLES to accurately capture the aerodynamics of glaze ice shapes without the need for additional modeling. In contrast, rime ice geometries required additional resolution to accurately represent the aerodynamic loads. This study demonstrates the effectiveness of the wall-modeled LES technique in simulating the complex aerodynamic effects of iced airfoils, providing valuable insights for aircraft design in icing environments and highlighting the importance of accurately representing ice geometries and roughness scales in simulations. △ Less

Submitted 22 September, 2023; originally announced September 2023.

Laboratory Study of Collisionless Magnetic Reconnection

Authors: H. Ji, J. Yoo, W. Fox, M. Yamada, M. Argall, J. Egedal, Y. -H. Liu, R. Wilder, S. Eriksson, W. Daughton, K. Bergstedt, S. Bose, J. Burch, R. Torbert, J. Ng, L. -J. Chen

Abstract: A concise review is given on the past two decades' results from laboratory experiments on collisionless magnetic reconnection in direct relation with space measurements, especially by Magnetospheric Multiscale (MMS) mission. Highlights include spatial structures of electromagnetic fields in ion and electron diffusion regions as a function of upstream symmetry and guide field strength; energy conve… ▽ More A concise review is given on the past two decades' results from laboratory experiments on collisionless magnetic reconnection in direct relation with space measurements, especially by Magnetospheric Multiscale (MMS) mission. Highlights include spatial structures of electromagnetic fields in ion and electron diffusion regions as a function of upstream symmetry and guide field strength; energy conversion and partition from magnetic field to ions and electrons including particle acceleration; electrostatic and electromagnetic kinetic plasma waves with various wavelengths; and plasmoid-mediated multiscale reconnection. Combined with the progress in theoretical, numerical, and observational studies, the physics foundation of fast reconnection in colisionless plasmas has been largely established, at least within the parameter ranges and spatial scales that were studied. Immediate and long-term future opportunities based on multiscale experiments and space missions supported by exascale computation are discussed, including dissipation by kinetic plasma waves, particle heating and acceleration, and multiscale physics across fluid and kinetic scales. △ Less

Submitted 13 July, 2023; originally announced July 2023.

Comments: 40 pages, 15 figures

Journal ref: ISSI book titled "Magnetic Reconnection: Explosive Energy Conversion in Space Plasmas" (2023)

Framework for Multi-messenger Inference from Neutron Stars: Combining Nuclear Theory Priors

Authors: Praveer Tiwari, Dake Zhou, Bhaskar Biswas, Michael McNeil Forbes, Sukanta Bose

Abstract: We construct an efficient parameterization of the pure neutron-matter equation of state (EoS) that incorporates the uncertainties from both chiral effective field theory ($χ$EFT) and phenomenological potential calculations. This parameterization yields a family of EoSs including and extending the forms based purely on these two calculations. In combination with an agnostic inner core EoS, this par… ▽ More We construct an efficient parameterization of the pure neutron-matter equation of state (EoS) that incorporates the uncertainties from both chiral effective field theory ($χ$EFT) and phenomenological potential calculations. This parameterization yields a family of EoSs including and extending the forms based purely on these two calculations. In combination with an agnostic inner core EoS, this parameterization is used in a Bayesian inference pipeline to obtain constraints on the e os parameters using multi-messenger observations of neutron stars. We specifically considered observations of the massive pulsar J0740+6620, the binary neutron star coalescence GW170817, and the NICER pulsar J0030+0451. Constraints on neutron star mass-radius relations are obtained and compared. The Bayes factors for the different EoS models are also computed. While current constraints do not reveal any significant preference among these models, the framework developed here may enable future observations with more sensitive detectors to discriminate them. △ Less

Submitted 25 June, 2024; v1 submitted 7 June, 2023; originally announced June 2023.

Report number: LIGO-P2300061

Laboratory study of the failed torus mechanism in arched, line-tied, magnetic flux ropes

Authors: Andrew Alt, Hantao Ji, Jongsoo Yoo, Sayak Bose, Aaron Goodman, Masaaki Yamada

Abstract: Coronal mass ejections (CMEs) are some of the most energetic and violent events in our solar system. The prediction and understanding of CMEs is of particular importance due to the impact that they can have on Earth-based satellite systems, and in extreme cases, ground-based electronics. CMEs often occur when long-lived magnetic flux ropes (MFRs) anchored to the solar surface destabilize and erupt… ▽ More Coronal mass ejections (CMEs) are some of the most energetic and violent events in our solar system. The prediction and understanding of CMEs is of particular importance due to the impact that they can have on Earth-based satellite systems, and in extreme cases, ground-based electronics. CMEs often occur when long-lived magnetic flux ropes (MFRs) anchored to the solar surface destabilize and erupt away from the Sun. One potential cause for these eruptions is an ideal magnetohydrodynamic (MHD) instability such as the kink or torus instability. Previous experiments on the Magnetic Reconnection eXperiment (MRX) revealed a class of MFRs that were torus-unstable but kink-stable, which failed to erupt. These "failed-tori" went through a process similar to Taylor relaxation where the toroidal current was redistributed before the eruption ultimately failed. We have investigated this behavior through additional diagnostics that measure the current distribution at the foot points and the energy distribution before and after an event. These measurements indicate that ideal MHD effects are sufficient to explain the energy distribution changes during failed torus events. This excludes Taylor relaxation as a possible mechanism of current redistribution during an event. A new model that only requires non-ideal effects in a thin layer above the electrodes is presented to explain the observed phenomena. This work broadens our understanding of the stability of MFRs and the mechanism behind the failed torus through the improved prediction of the torus instability and through new diagnostics to measure the energy inventory and current profile at the foot points. △ Less

Submitted 20 January, 2023; originally announced January 2023.

Comments: 20 pages, 18 figures. Submitted to Physics of Plasmas

Spicules in IRIS Mg II Observations: Automated Identification

Authors: Vicki L. Herde, Phillip C. Chamberlin, Don Schmit, Souvik Bose, Adrian Daw, Ryan O. Milligan, Vanessa Polito

Abstract: We have developed an algorithm to identify solar spicules in the first ever systematic survey of on-disk spicules exclusively using Mg II spectral observations. Using this algorithm we identify 2021 events in three Interface Region Imaging Spectrograph (IRIS) data sets with unique solar feature targets spanning a total of 300 minutes: (1) active region, (2) decayed active region/active network, an… ▽ More We have developed an algorithm to identify solar spicules in the first ever systematic survey of on-disk spicules exclusively using Mg II spectral observations. Using this algorithm we identify 2021 events in three Interface Region Imaging Spectrograph (IRIS) data sets with unique solar feature targets spanning a total of 300 minutes: (1) active region, (2) decayed active region/active network, and (3) coronal hole. We present event statistics and relate occurrence rates to the underlying photospheric magnetic field strength. This method identifies spicule event densities and occurrence rates similar to previous studies performed using Hα and Ca II observations of active regions. Additionally, this study identifies spicule-like events at very low rates at magnetic field intensities below 20 G, and increasing significantly between 100 and 200 G in active regions and above 20 G in coronal holes, which can be used to inform future observation campaigns. This information can be be used to help characterize spicules over their full lifetimes, and compliments existing Hα spectral capabilities and upcoming Lyα spectral observations with the Solar eruptioN Integral Field Spectrograph (SNIFS) sounding rocket. In total, this study presents a method for detecting solar spicules exclusively using Mg II spectra, and provides statistics for spicule occurrences in the Mg II h line with respect to the magnetic field strength for the purpose of predicting spicule occurrences. △ Less

Submitted 7 April, 2023; v1 submitted 9 December, 2022; originally announced December 2022.

Comments: 15 pages, 9 figures, presented at the AGU Fall 2022 conference, Submitted to APJ, published Apr 1 2023

Journal ref: ApJ 946 103 (2023)

Two-color pulse compounds in waveguides with a zero-nonlinearity point

Authors: O. Melchert, S. Bose, S. Willms, I. Babushkin, U. Morgner, A. Demircan

Abstract: We study incoherently coupled two-frequency pulse compounds in waveguides with single zero-dispersion and zero-nonlinearity points. In such waveguides, supported by a negative nonlinearity, soliton dynamics can be obtained even in domains of normal dispersion. We demonstrate trapping of weak pulses by solitary-wave wells, forming nonlinear-photonics meta-atoms, and molecule-like bound-states of pu… ▽ More We study incoherently coupled two-frequency pulse compounds in waveguides with single zero-dispersion and zero-nonlinearity points. In such waveguides, supported by a negative nonlinearity, soliton dynamics can be obtained even in domains of normal dispersion. We demonstrate trapping of weak pulses by solitary-wave wells, forming nonlinear-photonics meta-atoms, and molecule-like bound-states of pulses. We study the impact of Raman effect on these pulse compounds, finding that, depending on the precise subpulse configuration, they decelerate, accelerate, or are completely unaffected. Our results extend the range of systems in which two-frequency pulse compounds can be expected to exist and demonstrate further unique and unexpected behavior. △ Less

Submitted 1 November, 2022; originally announced November 2022.

Cherenkov radiation and scattering of external dispersive waves by two-color solitons

Authors: Ivan Oreshnikov, Oliver Melchert, Stephanie Willms, Surajit Bose, Ihar Babushkin, Ayhan Demircan, Uwe Morgner, Alexey Yulin

Abstract: For waveguides with two separate regions of anomalous dispersion, it is possible to create a quasi-stable two-color solitary wave. In this paper we consider how those waves interact with dispersive radiation, both generation of Cherenkov radiation and scattering of incident dispersive waves. We derive the analytic resonance conditions and verify them through numeric experiments. We also report inc… ▽ More For waveguides with two separate regions of anomalous dispersion, it is possible to create a quasi-stable two-color solitary wave. In this paper we consider how those waves interact with dispersive radiation, both generation of Cherenkov radiation and scattering of incident dispersive waves. We derive the analytic resonance conditions and verify them through numeric experiments. We also report incident radiation driving the internal oscillations of the soliton during the scattering process in case of an intense incident radiation. We generalize the resonance conditions for the case of an oscillating soliton and demonstrate how one can use the scattering process to probe and excite an internal mode of two-color soliton molecules. △ Less

Submitted 7 July, 2022; originally announced July 2022.

Comments: 9 pages, 7 figures

Multimode non-Gaussian secure communication under mode-mismatch

Authors: Soumyakanti Bose, Hyunseok Jeong

Abstract: In this paper, we analyse the role of non-Gaussianity in continuous-variable (CV) quantum key distribution (QKD) with multimode light under mode-mismatch. We consider entanglement-based protocol with non-Gaussian resources generated by single-photon-subtraction and zero-photon-catalysis on a two-mode squeezed vacuum state (TMSV). Our results indicate that, compared to the case of TMSV, these non-G… ▽ More In this paper, we analyse the role of non-Gaussianity in continuous-variable (CV) quantum key distribution (QKD) with multimode light under mode-mismatch. We consider entanglement-based protocol with non-Gaussian resources generated by single-photon-subtraction and zero-photon-catalysis on a two-mode squeezed vacuum state (TMSV). Our results indicate that, compared to the case of TMSV, these non-Gaussian resources reasonably enhances the performance of CV-QKD, even under the effect of noise arising due to mode-mismatch. To be specific, while in the case of TMSV the maximum transmission distance is limited to 47 Km, single-photon subtracted TMSV and zero-photon-catalysed TMSV yield much higher distance of 73 Km and 152 Km respectively. However, photon loss as a practical concern in zero-photon-catalysis setup limits the transmission distance for zero-photon-catalysed TMSV to 36 Km. This makes single-photon-subtraction on TMSV to be the best choice for entanglement-based CV-QKD in obtaining large transmission distance. Nonetheless, we note that the non-Gaussianity does not improve the robustness of entanglement-based CV-QKD scheme against detection inefficiency. We believe that our work provides a practical view of implementing CV-QKD with multimode light under realistic conditions. △ Less

Submitted 28 June, 2022; originally announced June 2022.

Comments: 8 pages, 9 figures

Two-dimensional plasma density evolution local to the inversion layer during sawtooth crash events using Beam Emission Spectroscopy

Authors: Sayak Bose, William Fox, Dingyun Liu, Zheng Yan, George McKee, Aaron Goodman, Hantao Ji

Abstract: We present methods for analyzing Beam Emission Spectroscopy (BES) data to obtain the plasma density evolution associated with rapid sawtooth crash events at the DIII-D tokamak. BES allows coverage over a 2-D spatial plane, inherently local measurements, with fast time responses, and therefore provides a valuable new channel for data during sawtooth events. A method is developed to remove sawtooth-… ▽ More We present methods for analyzing Beam Emission Spectroscopy (BES) data to obtain the plasma density evolution associated with rapid sawtooth crash events at the DIII-D tokamak. BES allows coverage over a 2-D spatial plane, inherently local measurements, with fast time responses, and therefore provides a valuable new channel for data during sawtooth events. A method is developed to remove sawtooth-induced edge-light pulses contained in the BES data. The edge light pulses appear to be from the $\rm{D}_α$ emission produced by edge recycling during sawtooth events, and are large enough that traditional spectroscopic filtering and data analysis techniques are insufficient to deduce physically meaningful quantities. A cross-calibration of 64 BES channels is performed using a novel method to ensure accurate measurements. For the large-amplitude density oscillations observed, we discuss and use the non-linear relationship between BES signal $δI/I_{0}$ and plasma density variation $δn_{e}/n_{e0}$. 2-D BES images cover a 8~cm~$\times$~20~cm region around the sawtooth inversion layer and show large-amplitude density oscillations, with additional significant spatial variations across the inversion layer, which grows and peaks near the time of the temperature crash. The edge light removal technique and method of converting large-amplitude $δI/I_{0}$ to $δn_{e}/n_{e0}$ presented here may help analyze other impulsive MHD phenomena in tokamaks. △ Less

Submitted 15 April, 2022; originally announced April 2022.

Collective states of active particles with elastic dipolar interactions

Authors: Subhaya Bose, Patrick S. Noerr, Ajay Gopinathan, Arvind Gopinath, Kinjal Dasbiswas

Abstract: Many types of mammalian cells exert active contractile forces and mechanically deform their elastic substrate, to accomplish biological functions such as cell migration. These substrate deformations provide a mechanism by which cells can sense other cells, leading to long range mechanical intercell interactions and possible self organization. Here, we treat cells as noisy motile particles that exe… ▽ More Many types of mammalian cells exert active contractile forces and mechanically deform their elastic substrate, to accomplish biological functions such as cell migration. These substrate deformations provide a mechanism by which cells can sense other cells, leading to long range mechanical intercell interactions and possible self organization. Here, we treat cells as noisy motile particles that exert contractile dipolar stresses on elastic substrates as they move. By combining this minimal model for the motility of individual cells with a linear elastic model that accounts for substrate mediated cell cell interactions, we examine emergent collective states that result from the interplay of cell motility and long range elastic dipolar interactions. In particular, we show that particles self assemble into flexible, motile chains which can cluster to form diverse larger scale compact structures with polar order. By computing key structural and dynamical metrics, we distinguish between the collective states at weak and strong elastic interactions, as well as at low and high motility. We also show how these states are affected by confinement, an important characteristic of the complex mechanical microenvironment inhabited by cells. Our model predictions are generally applicable to active matter with dipolar interactions ranging from biological cells to synthetic colloids endowed with electric or magnetic dipole moments. △ Less

Submitted 21 February, 2022; originally announced February 2022.

Comments: 14 pages, 8 figures, Submitted to Frontiers in Physics: Soft Matter Physics - Special Issue

SiGMa-Net: Deep learning network to distinguish binary black hole signals from short-duration noise transients

Authors: Sunil Choudhary, Anupreeta More, Sudhagar Suyamprakasam, Sukanta Bose

Abstract: Blip glitches, a type of short-duration noise transient in the LIGO--Virgo data, are a nuisance for the binary black hole (BBH) searches. They affect the BBH search sensitivity significantly because their time-domain morphologies are very similar, and that creates difficulty in vetoing them. In this work, we construct a deep-learning neural network to efficiently distinguish BBH signals from blip… ▽ More Blip glitches, a type of short-duration noise transient in the LIGO--Virgo data, are a nuisance for the binary black hole (BBH) searches. They affect the BBH search sensitivity significantly because their time-domain morphologies are very similar, and that creates difficulty in vetoing them. In this work, we construct a deep-learning neural network to efficiently distinguish BBH signals from blip glitches. We introduce sine-Gaussian projection (SGP) maps, which are projections of GW frequency-domain data snippets on a basis of sine-Gaussians defined by the quality factor and central frequency. We feed the SGP maps to our deep-learning neural network, which classifies the BBH signals and blips. Whereas the BBH signals are simulated, the blips used are taken from real data throughout our analysis. We show that our network significantly improves the identification of the BBH signals in comparison to the results obtained using traditional-$χ^2$ and sine-Gaussian $χ^2$. For example, our network improves the sensitivity by 75% at a false-positive rate of $10^{-2}$ for BBHs with total mass in the range $[80,140]~M_{\odot}$ and SNR in the range $[3,8]$. Also, it correctly identifies 95% of the real GW events in GWTC-3. The computation time for classification is a few minutes for thousands of SGP maps on a single core. With further optimisation in the next version of our algorithm, we expect a further reduction in the computational cost. Our proposed method can potentially improve the veto process in the LIGO--Virgo GW data analysis and conceivably support identifying GW signals in low-latency pipelines. △ Less

Submitted 17 February, 2022; originally announced February 2022.

Comments: 11 pages, 8 figures and 2 tables. Reviewed by LIGO Scientific Collaboration (LSC) with preprint number LIGO-P2100485

Non-Boussinesq subgrid-scale model with dynamic tensorial coefficients

Authors: Rahul Agrawal, Michael P. Whitmore, Kevin P. Griffin, Sanjeeb T. Bose, Parviz Moin

Abstract: A major drawback of Boussinesq-type subgrid-scale stress models used in large-eddy simulations is the inherent assumption of alignment between large-scale strain rates and filtered subgrid-stresses. A priori analyses using direct numerical simulation (DNS) data has shown that this assumption is invalid locally as subgrid-scale stresses are poorly correlated with the large-scale strain rates [Bardi… ▽ More A major drawback of Boussinesq-type subgrid-scale stress models used in large-eddy simulations is the inherent assumption of alignment between large-scale strain rates and filtered subgrid-stresses. A priori analyses using direct numerical simulation (DNS) data has shown that this assumption is invalid locally as subgrid-scale stresses are poorly correlated with the large-scale strain rates [Bardina et al., AIAA 1980; Meneveau and Liu, Ann. Rev. Fluid Mech. 2002]. In the present work, a new, non-Boussinesq subgrid-scale model is presented where the model coefficients are computed dynamically. Some previous non-Boussinesq models have observed issues in providing adequate dissipation of turbulent kinetic energy [e.g.: Bardina et al., AIAA 1980; Clark et al. J. Fluid Mech., 1979; Stolz and Adams, Phys. of Fluids, 1999]; however, the present model is shown to provide sufficient dissipation using dynamic coefficients. Modeled subgrid-scale Reynolds stresses satisfy the consistency requirements of the governing equations for LES, vanish in laminar flow and at solid boundaries, and have the correct asymptotic behavior in the near-wall region of a turbulent boundary layer. The new model, referred to as the dynamic tensor-coefficient Smagorinsky model (DTCSM), has been tested in simulations of canonical flows: decaying and forced homogeneous isotropic turbulence (HIT), and wall-modeled turbulent channel flow at high Reynolds numbers; the results show favorable agreement with DNS data. In order to assess the performance of DTCSM in more complex flows, wall-modeled simulations of high Reynolds number flow over a Gaussian bump exhibiting smooth-body flow separation are performed. Predictions of surface pressure and skin friction, compared against DNS and experimental data, show improved accuracy from DTCSM in comparison to the existing static coefficient (Vreman) and dynamic Smagorinsky model. △ Less

Submitted 3 May, 2022; v1 submitted 11 February, 2022; originally announced February 2022.

Comments: Revised Manuscript, under Review, Physical Review Fluids

Journal ref: Phys. Rev. Fluids 7 (7), 2022

One-pot Liquid-Phase Synthesis of MoS$_2$-WS$_2$ van der Waals Heterostructures for Broadband Photodetection

Authors: Shaona Bose, Subhrajit Mukherjee, Subhajit Jana, Sanjeev Kumar Srivastava, Samit Kumar Ray

Abstract: Two dimensional (2D) van der Waals heterostructures (vdWHs) have their unique potential in facilitating the stacking of layers of different 2D materials for optoelectronic devices with superior characteristics at a reduced cost. However, the fabrication of large area all-2D heterostructures is still challenging towards realizing practical devices. In the present work, we have demonstrated a rapid… ▽ More Two dimensional (2D) van der Waals heterostructures (vdWHs) have their unique potential in facilitating the stacking of layers of different 2D materials for optoelectronic devices with superior characteristics at a reduced cost. However, the fabrication of large area all-2D heterostructures is still challenging towards realizing practical devices. In the present work, we have demonstrated a rapid yet simple, impurity free and highly efficient sonication-assisted chemical exfoliation approach to synthesize hybrid vdWHs based on 2D molybdenum disulphide (MoS$_2$) and tungsten disulphide (WS$_2$), with high yield. Microscopic and spectroscopic studies have confirmed the successful exfoliation of layered 2D materials and formation of their hybrid heterostructure. The co-existence of 2D MoS2 and WS2 in the vdW hybrid is established by optical absorption and Raman shift measurements along with their chemical stiochiometry determined by X-ray photoelectron spectroscopy. The spectral response of the vdWH/Si (2D/3D) heterojunction photodetector fabricated using the as-synthesized material is found to show superior broadband photoresponse compared to that shown by the individual 2D MoS$_2$ and WS$_2$ based devices. The peak responsivity is found to be ~2.15 A/W at a wavelength of ~560 nm for an applied bias of -5 V. The ease of fabrication and superior performance of the chemically synthesized vdWH-based devices have revealed their potential use for large area optoelectronic applications on Si compatible CMOS platforms. △ Less

Submitted 27 July, 2021; originally announced August 2021.

Comments: Total 25 pages and 12 figures including supporting data

Performance of wall-modeled LES with boundary-layer-conforming grids for external aerodynamics

Authors: Adrián Lozano-Durán, Sanjeeb T. Bose, Parviz Moin

Abstract: We investigate the error scaling and computational cost of wall-modeled large-eddy simulation (WMLES) for external aerodynamic applications. The NASA Juncture Flow is used as representative of an aircraft with trailing-edge smooth-body separation. Two gridding strategies are examined: i) constant-size grid, in which the near-wall grid size has a constant value and ii) boundary-layer-conforming gri… ▽ More We investigate the error scaling and computational cost of wall-modeled large-eddy simulation (WMLES) for external aerodynamic applications. The NASA Juncture Flow is used as representative of an aircraft with trailing-edge smooth-body separation. Two gridding strategies are examined: i) constant-size grid, in which the near-wall grid size has a constant value and ii) boundary-layer-conforming grid (BL-conforming grid), in which the grid size varies to accommodate the growth of the boundary-layer thickness. Our results are accompanied by a theoretical analysis of the cost and expected error scaling for the mean pressure coefficient ($C_p$) and mean velocity profiles. The prediction of $C_p$ is within less than $5\%$ error for all the grids studied, even when the boundary layers are marginally resolved. The high accuracy in the prediction of $C_p$ is attributed to the outer-layer nature of the mean pressure in attached flows. The errors in the predicted mean velocity profiles exhibit a large variability depending on the location considered, namely, fuselage, wing-body juncture, or separated trailing-edge. WMLES performs as expected in regions where the flow resembles a zero-pressure-gradient turbulent boundary layer such as the fuselage ($<5\%$ error). However, there is a decline in accuracy of WMLES predictions of mean velocities in the vicinity of wing-body junctions and, more acutely, in separated zones. The impact of the propagation of errors from the underresolved wing leading-edge is also investigated. It is shown that BL-conforming grids enable a higher accuracy in wing-body junctions and separated regions due to the more effective distribution of grid points, which in turn diminishes the streamwise propagation of errors. △ Less

Submitted 3 July, 2021; originally announced July 2021.

Comments: arXiv admin note: text overlap with arXiv:2101.00331

Spin dynamical decoupling for generating macroscopic superpositions of a free-falling nanodiamond

Authors: B. D. Wood, S. Bose, G. W. Morley

Abstract: Levitated nanodiamonds containing negatively charged nitrogen-vacancy centers (${\text{NV}}^{-}$) have been proposed as a platform to generate macroscopic spatial superpositions. Requirements for this include having a long ${\text{NV}}^{-}$ spin coherence time, which necessitates formulating a dynamical decoupling strategy in which the regular spin flips do not cancel the growth of the superpositi… ▽ More Levitated nanodiamonds containing negatively charged nitrogen-vacancy centers (${\text{NV}}^{-}$) have been proposed as a platform to generate macroscopic spatial superpositions. Requirements for this include having a long ${\text{NV}}^{-}$ spin coherence time, which necessitates formulating a dynamical decoupling strategy in which the regular spin flips do not cancel the growth of the superposition through the Stern-Gerlach effect in an inhomogeneous magnetic field. Here, we propose a scheme to place a $250$-nm-diameter diamond in a superposition with spatial separation of over $250$ nm, while incorporating dynamical decoupling. We achieve this by letting a diamond fall for $2.4$ m through a magnetic structure, including $1.13$ m in an inhomogeneous region generated by magnetic teeth. △ Less

Submitted 31 January, 2022; v1 submitted 5 May, 2021; originally announced May 2021.

Comments: Version 1: 6 pages, 2 figures. Supersedes arXiv:1810.07045 [quant-ph]. Version 2: 11 pages, 5 figures. Removed nanodiamond spin coherence time results as they can now be found in arXiv:2112.01899 [cond-mat.mes-hall]. Added additional details and figures as appendices, and in the discussion section. Version 3: 11 pages, 5 figures. Figures edited to work in grayscale, title change

Journal ref: Physical Review A 105, 012824 (2022)

Performance of wall-modeled LES for external aerodynamics in the NASA Juncture Flow

Authors: Adrián Lozano-Durán, Sanjeeb T. Bose, Parviz Moin

Abstract: We investigate the performance of wall-modeled LES for external aerodynamics in the NASA Juncture Flow. We characterize the errors in the prediction of mean velocity profiles and pressure coefficient for three different locations over the aircraft: the upstream region of the fuselage, the wing-body juncture, and the wing-body juncture close to the trailing-edge. The last two locations are characte… ▽ More We investigate the performance of wall-modeled LES for external aerodynamics in the NASA Juncture Flow. We characterize the errors in the prediction of mean velocity profiles and pressure coefficient for three different locations over the aircraft: the upstream region of the fuselage, the wing-body juncture, and the wing-body juncture close to the trailing-edge. The last two locations are characterized by strong mean-flow three-dimensionality and separation. The message conveyed by our error analysis is that WMLES performs as expected in regions where the flow resembles a zero-pressure-gradient flat plate boundary layer. However, there is a clear decline of the current models in the presence of wing-body junctions and, more acutely, in separated zones. The slow convergence to the solution in these regions renders the brute-force grid-refinement approach to improve the accuracy of the solution unfeasible. The results reported above pertain to the mean velocity profile predicted using the typical grid resolution for external aerodynamics applications, i.e., 5--20 points per boundary-layer thickness. The prediction of the pressure coefficient is below 5\% error for all grid sizes considered, even when boundary layers were marginally resolved. The latter accuracy can be attributed to the outer-layer nature of the mean pressure, which becomes less sensitive to flow details within the turbulent boundary layer. Finally, we show that boundary-layer-conforming grids (i.e., grids maintaining a constant number of points per boundary-layer thickness) allow for a more efficient distribution of grid points and smaller errors. Our results suggest that novel modeling venues encompassing physical insights, together with numerical and gridding advancements, must be exploited to attain predictions within the tolerance required for Certification by Analysis. △ Less

Submitted 1 January, 2021; originally announced January 2021.

Journal ref: Annual Research Briefs, Center for Turbulence Research (Stanford University), 2020

Multi-Channel Auto-Calibration for the Atmospheric Imaging Assembly using Machine Learning

Authors: Luiz F. G. dos Santos, Souvik Bose, Valentina Salvatelli, Brad Neuberg, Mark C. M. Cheung, Miho Janvier, Meng Jin, Yarin Gal, Paul Boerner, Atılım Güneş Baydin

Abstract: Solar activity plays a quintessential role in influencing the interplanetary medium and space-weather around the Earth. Remote sensing instruments onboard heliophysics space missions provide a pool of information about the Sun's activity via the measurement of its magnetic field and the emission of light from the multi-layered, multi-thermal, and dynamic solar atmosphere. Extreme UV (EUV) waveleng… ▽ More Solar activity plays a quintessential role in influencing the interplanetary medium and space-weather around the Earth. Remote sensing instruments onboard heliophysics space missions provide a pool of information about the Sun's activity via the measurement of its magnetic field and the emission of light from the multi-layered, multi-thermal, and dynamic solar atmosphere. Extreme UV (EUV) wavelength observations from space help in understanding the subtleties of the outer layers of the Sun, namely the chromosphere and the corona. Unfortunately, such instruments, like the Atmospheric Imaging Assembly (AIA) onboard NASA's Solar Dynamics Observatory (SDO), suffer from time-dependent degradation, reducing their sensitivity. Current state-of-the-art calibration techniques rely on periodic sounding rockets, which can be infrequent and rather unfeasible for deep-space missions. We present an alternative calibration approach based on convolutional neural networks (CNNs). We use SDO-AIA data for our analysis. Our results show that CNN-based models could comprehensively reproduce the sounding rocket experiments' outcomes within a reasonable degree of accuracy, indicating that it performs equally well compared with the current techniques. Furthermore, a comparison with a standard "astronomer's technique" baseline model reveals that the CNN approach significantly outperforms this baseline. Our approach establishes the framework for a novel technique to calibrate EUV instruments and advance our understanding of the cross-channel relation between different EUV channels. △ Less

Submitted 1 February, 2021; v1 submitted 27 December, 2020; originally announced December 2020.

Comments: 12 pages, 7 figures, 8 tables. This is a pre-print of an article submitted and accepted by A&A Journal

Journal ref: A&A 648, A53 (2021)

Realization of a complete Stern-Gerlach interferometer: Towards a test of quantum gravity

Authors: Yair Margalit, Or Dobkowski, Zhifan Zhou, Omer Amit, Yonathan Japha, Samuel Moukouri, Daniel Rohrlich, Anupam Mazumdar, Sougato Bose, Carsten Henkel, Ron Folman

Abstract: The Stern-Gerlach effect, discovered a century ago, has become a paradigm of quantum mechanics. Surprisingly there has been little evidence that the original scheme with freely propagating atoms exposed to gradients from macroscopic magnets is a fully coherent quantum process. Specifically, no full-loop Stern-Gerlach interferometer has been realized with the scheme as envisioned decades ago. Furth… ▽ More The Stern-Gerlach effect, discovered a century ago, has become a paradigm of quantum mechanics. Surprisingly there has been little evidence that the original scheme with freely propagating atoms exposed to gradients from macroscopic magnets is a fully coherent quantum process. Specifically, no full-loop Stern-Gerlach interferometer has been realized with the scheme as envisioned decades ago. Furthermore, several theoretical studies have explained why such an interferometer is a formidable challenge. Here we provide a detailed account of the first full-loop Stern-Gerlach interferometer realization, based on highly accurate magnetic fields, originating from an atom chip, that ensure coherent operation within strict constraints described by previous theoretical analyses. Achieving this high level of control over magnetic gradients is expected to facilitate technological as well as fundamental applications, such as probing the interface of quantum mechanics and gravity. While the experimental realization described here is for a single atom, future challenges would benefit from utilizing macroscopic objects doped with a single spin. Specifically, we show that such an experiment is in principle feasible, opening the door to a new era of fundamental probes. △ Less

Submitted 21 November, 2020; originally announced November 2020.

Journal ref: Science Advances 7 (2021) eabg2879

Shock-induced heating and transition to turbulence in a hypersonic boundary layer

Authors: Lin Fu, Michael Karp, Sanjeeb T. Bose, Parviz Moin, Javier Urzay

Abstract: The interaction between an incident shock wave and a Mach-6 undisturbed hypersonic laminar boundary layer over a cold wall is addressed using direct numerical simulations (DNS) and wall-modeled large-eddy simulations (WMLES) at different angles of incidence. At sufficiently high shock-incidence angles, the boundary layer transitions to turbulence via breakdown of near-wall streaks shortly downstre… ▽ More The interaction between an incident shock wave and a Mach-6 undisturbed hypersonic laminar boundary layer over a cold wall is addressed using direct numerical simulations (DNS) and wall-modeled large-eddy simulations (WMLES) at different angles of incidence. At sufficiently high shock-incidence angles, the boundary layer transitions to turbulence via breakdown of near-wall streaks shortly downstream of the shock impingement, without the need of any inflow free-stream disturbances. The transition causes a localized significant increase in the Stanton number and skin-friction coefficient, with high incidence angles augmenting the peak thermomechanical loads in an approximately linear way. Statistical analyses of the boundary layer downstream of the interaction for each case are provided that quantify streamwise spatial variations of the Reynolds analogy factors and indicate a breakdown of the Morkovin's hypothesis near the wall, where velocity and temperature become correlated. A modified strong Reynolds analogy with a fixed turbulent Prandtl number is observed to perform best. Conventional transformations fail at collapsing the mean velocity profiles on the incompressible log law. The WMLES prompts transition and peak heating, delays separation, and advances reattachment, thereby shortening the separation bubble. When the shock leads to transition, WMLES provides predictions of DNS peak thermomechanical loads within $\pm 10\%$ at a computational cost lower than DNS by two orders of magnitude. Downstream of the interaction, in the turbulent boundary layer, WMLES agrees well with DNS results for the Reynolds analogy factor, the mean profiles of velocity and temperature, including the temperature peak, and the temperature/velocity correlation. △ Less

Submitted 20 October, 2020; originally announced October 2020.

Comments: 48 pages, 36 figures

MSC Class: 76K05; 76N06; 76N20; 76F06; 76F40; 76F50; 76F65; 76F02