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Higher-dimensional operators and Polyakov loop in hot Scalar QED from the heat kernel
Authors:
Siddhartha Bandyopadhyay,
Joydeep Chakrabortty,
Debmalya Dey,
Philipp Schicho,
Tushar
Abstract:
Using the finite-temperature heat kernel method, we compute the gauge-invariant effective Lagrangian up to dimension-six for massive hot scalar QED. We propose two complementary methods: integrating out heavy modes at finite temperature, and deriving the finite-temperature heat kernel coefficients from the zero-temperature ones. We show that in the static limit, both lead to the same three-dimensi…
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Using the finite-temperature heat kernel method, we compute the gauge-invariant effective Lagrangian up to dimension-six for massive hot scalar QED. We propose two complementary methods: integrating out heavy modes at finite temperature, and deriving the finite-temperature heat kernel coefficients from the zero-temperature ones. We show that in the static limit, both lead to the same three-dimensional effective operators. We also compute the gauge-invariant Coleman-Weinberg effective potential for a constant background at finite temperature. We further examine how the Polyakov loop modifies the matching coefficients and assess its impact together with the higher-dimensional operators on the thermodynamics of cosmological first-order phase transitions, which in turn can affect an associated gravitational-wave spectrum.
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Submitted 8 June, 2026;
originally announced June 2026.
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Non-perturbative heavy quark diffusion coefficients in arbitrarily magnetized quark-gluon plasma
Authors:
Debarshi Dey,
Aritra Bandyopadhyay,
Yifeng Sun,
Santosh K. Das
Abstract:
Heavy quark (HQ) momentum ($κ$) and spatial diffusion ($D_s$) coefficients are computed in a non-perturbative thermal QCD medium in the presence of a background magnetic field of arbitrary strength. Both perturbative and non-perturbative effects are incorporated via the in-medium HQ potential, obtained from the resummed gluon propagator. We find that the momentum diffusion coefficients become anis…
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Heavy quark (HQ) momentum ($κ$) and spatial diffusion ($D_s$) coefficients are computed in a non-perturbative thermal QCD medium in the presence of a background magnetic field of arbitrary strength. Both perturbative and non-perturbative effects are incorporated via the in-medium HQ potential, obtained from the resummed gluon propagator. We find that the momentum diffusion coefficients become anisotropic even in the static heavy quark limit, with the magnetic field direction defining the axis of anisotropy. This anisotropy originates from restrictions on longitudinal momentum diffusion in the gluon spectral function, and naturally leads to two spatial diffusion coefficients ($D_s^L$, $D_s^T$). Non-perturbative effects are found to be dominant at low temperatures. These results provide a more consistent input for Langevin based calculations of the heavy quark directed flow at RHIC and LHC energies.
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Submitted 10 July, 2026; v1 submitted 27 April, 2026;
originally announced April 2026.
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Core or Halo? Two-Fluid Analysis of Dark Matter-Admixed Quarkyonic Stars in the Multi-Messenger Era
Authors:
Jeet Amrit Pattnaik,
D. Dey,
M. Bhuyan,
R. N. Panda,
S. K. Patra
Abstract:
For the first time, we explore dark matter (DM) admixed quarkyonic stars (DAQSs) within a two-fluid formalism, where the normal/visible sector is modeled by a quarkyonic equation of state (EOS) in the Effective Relativistic Mean Field (E-RMF) framework and the DM component is treated as a degenerate fermionic gas with scalar and vector self-interactions. Our analysis begins with the mass-radius (M…
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For the first time, we explore dark matter (DM) admixed quarkyonic stars (DAQSs) within a two-fluid formalism, where the normal/visible sector is modeled by a quarkyonic equation of state (EOS) in the Effective Relativistic Mean Field (E-RMF) framework and the DM component is treated as a degenerate fermionic gas with scalar and vector self-interactions. Our analysis begins with the mass-radius (M-R) relation, showing that the inclusion of DM enables stellar configurations to reach the mass range compatible with the GW190814 event. We identify both DM core and DM halo morphologies among the viable EOSs, with core dominated and halo dominated cases exhibiting distinct signatures. By fixing the stellar mass within the GW190814 range, we constrain the possible dark matter fractions and explore the role of different interaction channels. Using the EOSs consistent with these constraints, we further investigate the tidal deformability ($Λ$), moment of inertia (MOI), and stellar radius, finding broad agreement with constraints from GW170817, GW190814, and NICER. Finally, we compile the characteristic properties of DAQSs, including EOS type, DM fractions, morphology (core vs halo), and macroscopic observables in a comparative summary. This study provides a unified two-fluid framework to explore dense QCD matter and dark matter in the multi-messenger era, suggesting that the GW190814 secondary object could plausibly be interpreted as either a DM core or a DM halo quarkyonic star.
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Submitted 8 September, 2025;
originally announced September 2025.
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Gauge Choices, Infrared Pitfalls, and Thermal Effects in Effective Potentials
Authors:
Debanjan Balui,
Tisa Biswas,
Joydeep Chakrabortty,
Debmalya Dey,
Christoph Englert,
Subhendra Mohanty
Abstract:
The evaluation of effective potentials is critical for a range of phenomenological applications, including inflation, vacuum stability, and phase transitions. A drawback arises from the gauge-dependence of the effective potential. Furthermore, in theories with spontaneous symmetry breaking, the effective potential exhibits infrared (IR) divergences in the limit of vanishing Goldstone masses. By co…
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The evaluation of effective potentials is critical for a range of phenomenological applications, including inflation, vacuum stability, and phase transitions. A drawback arises from the gauge-dependence of the effective potential. Furthermore, in theories with spontaneous symmetry breaking, the effective potential exhibits infrared (IR) divergences in the limit of vanishing Goldstone masses. By considering the multiplicative anomaly that arises due to non-factorisation of elliptic operators in the Fermi gauge when computing the effective potential at one-loop order, we demonstrate that its gauge independence and IR behaviour are improved to the corresponding findings of Landau gauge calculations simultaneously. The latter are straightforwardly and transparently reproduced using an approach that employs the Heat Kernel technique, thereby providing a shortcut to reflect anomaly-related cancellations from the outset. Our findings generalise to the treatment of the effective potential at finite temperature. In particular, the Heat Kernel extends gauge independence to any value of the expansion in mass over temperature.
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Submitted 30 July, 2025;
originally announced July 2025.
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Nonperturbative heavy quark diffusion coefficients in a weakly magnetized thermal QCD medium
Authors:
Debarshi Dey,
Aritra Bandyopadhyay,
Santosh K. Das,
Sadhana Dash,
Vinod Chandra,
Basanta K. Nandi
Abstract:
In this work, the perturbative and non-perturbative contributions to the heavy quark (HQ) momentum ($κ$) as well as spatial ($D_s$) diffusion coefficients are computed in a weak background magnetic field. The formalism adopted here involves calculation of the in-medium potential of the HQ in a weak magnetic field, which then serves as a proxy for the resummed gluon propagator in the calculation of…
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In this work, the perturbative and non-perturbative contributions to the heavy quark (HQ) momentum ($κ$) as well as spatial ($D_s$) diffusion coefficients are computed in a weak background magnetic field. The formalism adopted here involves calculation of the in-medium potential of the HQ in a weak magnetic field, which then serves as a proxy for the resummed gluon propagator in the calculation of HQ self-energy ($Σ$). The self-energy determines the scattering rate of HQs with light thermal partons, which is subsequently used to evaluate $κ$ and $D_s$. It is observed that non-perturbative effects play a dominant role at low temperature. The spatial diffusion coefficient $2πT D_s$, exhibits good agreement with recent LQCD results. These findings can be applied to calculate the heavy quark directed flow at RHIC and LHC energies. An extension of this formalism to the case of finite HQ momentum has also been attempted.
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Submitted 9 July, 2025; v1 submitted 3 April, 2025;
originally announced April 2025.
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Thermoelectric and heavy quark transport coefficients of hot QCD matter in the presence of magnetic field
Authors:
Debarshi Dey
Abstract:
The aim of this thesis is twofold: a) A comprehensive study of the thermoelectric response in QGP in the absence and presence of a background magnetic field, b) Exploring the dynamics of heavy quarks traversing in QGP in the presence of a weak background magnetic field.
We have evaluated the strength of the thermoelectric response in QGP quantified by the Seebeck and Nernst coefficients, first i…
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The aim of this thesis is twofold: a) A comprehensive study of the thermoelectric response in QGP in the absence and presence of a background magnetic field, b) Exploring the dynamics of heavy quarks traversing in QGP in the presence of a weak background magnetic field.
We have evaluated the strength of the thermoelectric response in QGP quantified by the Seebeck and Nernst coefficients, first in the absence of a background magnetic field, and then in the presence of a strong magnetic field. This is followed by the evaluation of the coefficients in the presence of a weak magnetic field. Each of the above-mentioned scenarios is investigated under the assumption that the QGP is isotropic. This assumption is then relaxed by using an anisotropic distribution for the quarks, and the calculations are repeated. The formalism adopted in the calculation of these coefficients is that of kinetic theory, particularly, the relativistic Boltzmann equation in the relaxation time approximation.
The other part of this thesis deals with heavy quark (HQ) dynamics in the QGP. HQs have been recognised as very good probes of the QGP owing to their large masses. We have calculated the HQ energy loss $dE/dx$, longitudinal and transverse momentum diffusion coeffcients $κL/T^3$ , and spatial diffusion coefficient $D_s$ , to leading order in the strong coupling $α$, for both charm and bottom quarks. We consider Coulomb scattering of the HQ with thermal quarks and gluons to evaluate the scattering rate from which, all the aforementioned coefficients are obtained. We find that the values of $κ$'s increase in the presence of a weak magnetic field (compared to the $B = 0$ case), and the anisotropy therein is also heightened in the presence of the magnetic field. $D_s$ is found to decrease in the presence of magnetic field, compared to its value at $B = 0$.
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Submitted 24 February, 2025;
originally announced February 2025.
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Gauge Invariant Effective Potential
Authors:
Debanjan Balui,
Joydeep Chakrabortty,
Debmalya Dey,
Subhendra Mohanty
Abstract:
We show that the long-standing problem of gauge dependence of the effective potential arises due to the factorisation of the determinant of operators, which is invalid when we take the zeta-regularised trace of the operators. We show by correcting for this assumption by computing the multiplicative anomaly, the gauge-dependent terms of the effective potential cancel. We also show that in two- and…
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We show that the long-standing problem of gauge dependence of the effective potential arises due to the factorisation of the determinant of operators, which is invalid when we take the zeta-regularised trace of the operators. We show by correcting for this assumption by computing the multiplicative anomaly, the gauge-dependent terms of the effective potential cancel. We also show that in two- and odd-dimensional non-compact spacetime manifolds where the multiplicative anomaly term is zero, the standard calculation of one-loop effective potential gives a gauge-independent result. These results are in support of our claim that the multiplicative anomaly may play a crucial role in removing the gauge dependence in the effective potential in the four-dimensional non-compact manifold. Noting the non-trivial aspects of this anomaly computation for a generic scenario, we propose the Heat-Kernel method to compute the effective potential where this anomaly emerges as a total derivative, thus redundant. We explicitly show how one can calculate the gauge independent, effective action and the Coleman-Weinberg effective potential by employing the Heat-Kernel method. Based on this result, we advocate the Heat-Kernel expansion as the most straightforward method, as it naturally deals with the matrix elliptic operator for the calculation of manifestly gauge independent, effective actions compared to other conventional methods.
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Submitted 24 February, 2025;
originally announced February 2025.
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Viscous effects of a hot QGP medium in time dependent magnetic field and their phenomenological significance
Authors:
Debarshi Dey,
Gowthama K K,
Sadhana Dash,
Basanta Kumar Nandi
Abstract:
In this work, we have studied, for the first time, the impact of a realistic picture of a time dependent electric and magnetic field on the shear and bulk viscosities of the medium. Both the electric and magnetic fields are considered to be exponentially decaying with time, and the study is valid in the regime where the magnetic field strength is weak ($eB\ll T^2$). The evaluation has been done in…
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In this work, we have studied, for the first time, the impact of a realistic picture of a time dependent electric and magnetic field on the shear and bulk viscosities of the medium. Both the electric and magnetic fields are considered to be exponentially decaying with time, and the study is valid in the regime where the magnetic field strength is weak ($eB\ll T^2$). The evaluation has been done in the kinetic theory framework wherein we have solved the relativistic Boltzmann transport equation within the relaxation time approximation collision kernel. We have shown that the constant weak field results as well as the $B=0$ results in the literature can be obtained as special cases of our general results. We have observed that the shear and bulk viscosities increase with time or equivalently, decrease with the strength of the magnetic field. To connect these observations with experiments, we have calculated the thermalization time, shear viscosity to entropy ratio ($η/s$), and bulk viscosity to entropy ratio ($ζ/s$).
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Submitted 14 May, 2025; v1 submitted 31 January, 2025;
originally announced January 2025.
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Two-loop dimension Six Effective Action: Integrating Out Heavy Scalar
Authors:
Nilabhra Adhikary,
Jaydeb Das,
Debmalya Dey
Abstract:
For the first time, we present the model-independent two-loop effective action up to dimension six after integrating out heavy scalar(s) employing the Heat-Kernel method. We compute the effective operators that emerge at two-loop for two example models: heavy electroweak complex Triplet and Doublet scalars. We present our results on the SILH basis. We also capture the effect in the fermion sector.…
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For the first time, we present the model-independent two-loop effective action up to dimension six after integrating out heavy scalar(s) employing the Heat-Kernel method. We compute the effective operators that emerge at two-loop for two example models: heavy electroweak complex Triplet and Doublet scalars. We present our results on the SILH basis. We also capture the effect in the fermion sector. For these two scenarios, we compute all the fermionic effective operators up to dimension six.
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Submitted 4 January, 2026; v1 submitted 2 January, 2025;
originally announced January 2025.
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Dynamics of Hot QCD Matter 2024 -- Hard Probes
Authors:
Santosh K. Das,
Prabhakar Palni,
Amal Sarkar,
Vineet Kumar Agotiya,
Aritra Bandyopadhyay,
Partha Pratim Bhaduri,
Saumen Datta,
Vaishnavi Desai,
Debarshi Dey,
Vincenzo Greco,
Mohammad Yousuf Jamal,
Gurleen Kaur,
Manisha Kumari,
Monideepa Maity,
Subrata Pal,
Binoy Krishna Patra,
Pooja,
Jai Prakash,
Manaswini Priyadarshini,
Vyshakh B R,
Marco Ruggieri,
Nihar Ranjan Sahoo,
Raghunath Sahoo,
Om Shahi,
Devanshu Sharma
, et al. (2 additional authors not shown)
Abstract:
The hot and dense QCD matter, known as the Quark-Gluon Plasma (QGP), is explored through heavy-ion collision experiments at the LHC and RHIC. Jets and heavy flavors, produced from the initial hard scattering, are used as hard probes to study the properties of the QGP. Recent experimental observations on jet quenching and heavy-flavor suppression have strengthened our understanding, allowing for fi…
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The hot and dense QCD matter, known as the Quark-Gluon Plasma (QGP), is explored through heavy-ion collision experiments at the LHC and RHIC. Jets and heavy flavors, produced from the initial hard scattering, are used as hard probes to study the properties of the QGP. Recent experimental observations on jet quenching and heavy-flavor suppression have strengthened our understanding, allowing for fine-tuning of theoretical models in hard probes. The second conference, HOT QCD Matter 2024, was organized to bring the community together for discussions on key topics in the field. This article comprises 15 sections, each addressing various aspects of hard probes in relativistic heavy-ion collisions, offering a snapshot of current experimental observations and theoretical advancements. The article begins with a discussion on memory effects in the quantum evolution of quarkonia in the quark-gluon plasma, followed by an experimental review, new insights on jet quenching at RHIC and LHC, and concludes with a machine learning approach to heavy flavor production at the Large Hadron Collider.
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Submitted 18 December, 2024;
originally announced December 2024.
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Thermoelectric response of a hot and weakly magnetized anisotropic QCD medium
Authors:
Salman Ahamad Khan,
Debarshi Dey,
Binoy krishna Patra
Abstract:
We have studied the Seebeck and Nernst coefficients of a weakly magnetized hot QCD medium having a weak momentum anisotropy within the kinetic theory approach. The thermal medium effects have been incorporated in the framework of a quasi-particle model where the medium dependent mass of the quark has been calculated using perturbative thermal QCD in the presence of a weak magnetic field which lead…
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We have studied the Seebeck and Nernst coefficients of a weakly magnetized hot QCD medium having a weak momentum anisotropy within the kinetic theory approach. The thermal medium effects have been incorporated in the framework of a quasi-particle model where the medium dependent mass of the quark has been calculated using perturbative thermal QCD in the presence of a weak magnetic field which leads to different masses for the left ($L$) and right ($R$) handed chiral quark modes. We have found that the Seebeck and Nernst coefficient magnitudes for the individual quark flavors as well as for the composite medium are decreasing functions of temperature and decreasing functions of anisotropy strength. The Nernst coefficient magnitudes are about an order of magnitude smaller than their Seebeck counterparts, indicating the Seebeck effect constitutes a stronger response than the Nernst effect. The average percentage change corresponding to switching between quasiparticle modes ($L\to R$ or $R\to L$) is an order of magnitude smaller for Nernst coefficients, compared to the Seebeck coefficients.
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Submitted 8 July, 2024; v1 submitted 15 September, 2023;
originally announced September 2023.
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Shear viscosity of rotating, hot, and dense spin-half fermionic systems from quantum field theory
Authors:
Sarthak Satapathy,
Rajeev Singh,
Pushpa Panday,
Salman Ahamad Khan,
Debarshi Dey
Abstract:
In this study, we calculate the shear viscosity for rotating fermions with spin-half under conditions of high temperature and density. We employ the Kubo formalism, rooted in finite-temperature quantum field theory, to compute the field correlation functions essential for this evaluation. The one-loop diagram pertinent to shear viscosity is analyzed within the context of curved space, utilizing te…
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In this study, we calculate the shear viscosity for rotating fermions with spin-half under conditions of high temperature and density. We employ the Kubo formalism, rooted in finite-temperature quantum field theory, to compute the field correlation functions essential for this evaluation. The one-loop diagram pertinent to shear viscosity is analyzed within the context of curved space, utilizing tetrad formalism as an effective approach in cylindrical coordinates. Our findings focus on extremely high angular velocities, ranging from 0.1 to 1 GeV, which align with experimental expectations. Furthermore, we explore the inter-relationship between the chemical potential and angular velocity within the scope of this study.
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Submitted 21 April, 2024; v1 submitted 11 September, 2023;
originally announced September 2023.
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Dynamics of heavy flavour in a weakly magnetized hot QCD medium
Authors:
Debarshi Dey,
Binoy krishna Patra
Abstract:
We obtain the spatial and momentum diffusion coefficients ($D_s$ and $κ$), and the collisional energy loss ($dE/dx$) of a heavy quark (HQ) traversing through a thermal medium of quarks and gluons in a weak magnetic field ($B$), for the two cases of the HQ moving either parallel or perpendicular to $\bm{B}$. For that purpose, we consider Coulomb scatterings ($t$-channel) of the HQ with the light qu…
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We obtain the spatial and momentum diffusion coefficients ($D_s$ and $κ$), and the collisional energy loss ($dE/dx$) of a heavy quark (HQ) traversing through a thermal medium of quarks and gluons in a weak magnetic field ($B$), for the two cases of the HQ moving either parallel or perpendicular to $\bm{B}$. For that purpose, we consider Coulomb scatterings ($t$-channel) of the HQ with the light quarks, obtained from the imaginary part of the HQ self-energy via the cutting rules. Both the normalised (by $T^3$) %\textit{momentum} diffusion coefficients, $κ$, as well as $dE/dx$, for charm quarks are larger than that for bottom quarks due to the larger mass of the latter. Also, the effect of $B$ is more feeble on the bottom quark, compared to the charm quark. Comparatively, the magnitudes of both $κ$ and $dE/dx$ are significantly smaller for the case of $\bm{v}\perp\bm{B}$. For both the cases, our results show that the momentum transfer between the HQ and the medium takes place preferentially along the direction of HQ velocity, thus leading to a significant increase in the momentum diffusion anisotropy, compared to $B=0$. We also calculate the (scaled) spatial diffusion coefficient, which we find to be independent of the heavy flavor mass and is almost unaffected by changes in $B$.
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Submitted 11 June, 2024; v1 submitted 1 July, 2023;
originally announced July 2023.
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Dynamics of Hot QCD Matter -- Current Status and Developments
Authors:
Santosh K. Das,
Prabhakar Palni,
Jhuma Sannigrahi,
Jan-e Alam,
Cho Win Aung,
Yoshini Bailung,
Debjani Banerjee,
Gergely Gábor Barnaföldi,
Subash Chandra Behera,
Partha Pratim Bhaduri,
Samapan Bhadury,
Rajesh Biswas,
Pritam Chakraborty,
Vinod Chandra,
Prottoy Das,
Sadhana Dash,
Saumen Datta,
Sudipan De,
Vaishnavi Desai,
Suman Deb,
Debarshi Dey,
Jayanta Dey,
Sabyasachi Ghosh,
Najmul Haque,
Mujeeb Hasan
, et al. (42 additional authors not shown)
Abstract:
The discovery and characterization of hot and dense QCD matter, known as Quark Gluon Plasma (QGP), remains the most international collaborative effort and synergy between theorists and experimentalists in modern nuclear physics to date. The experimentalists around the world not only collect an unprecedented amount of data in heavy-ion collisions, at Relativistic Heavy Ion Collider (RHIC), at Brook…
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The discovery and characterization of hot and dense QCD matter, known as Quark Gluon Plasma (QGP), remains the most international collaborative effort and synergy between theorists and experimentalists in modern nuclear physics to date. The experimentalists around the world not only collect an unprecedented amount of data in heavy-ion collisions, at Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory (BNL) in New York, USA, and the Large Hadron Collider (LHC), at CERN in Geneva, Switzerland but also analyze these data to unravel the mystery of this new phase of matter that filled a few microseconds old universe, just after the Big Bang. In the meantime, advancements in theoretical works and computing capability extend our wisdom about the hot-dense QCD matter and its dynamics through mathematical equations. The exchange of ideas between experimentalists and theoreticians is crucial for the progress of our knowledge. The motivation of this first conference named "HOT QCD Matter 2022" is to bring the community together to have a discourse on this topic. In this article, there are 36 sections discussing various topics in the field of relativistic heavy-ion collisions and related phenomena that cover a snapshot of the current experimental observations and theoretical progress. This article begins with the theoretical overview of relativistic spin-hydrodynamics in the presence of the external magnetic field, followed by the Lattice QCD results on heavy quarks in QGP, and finally, it ends with an overview of experiment results.
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Submitted 29 August, 2022;
originally announced August 2022.
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Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A$^*$
Authors:
Sunny Vagnozzi,
Rittick Roy,
Yu-Dai Tsai,
Luca Visinelli,
Misba Afrin,
Alireza Allahyari,
Parth Bambhaniya,
Dipanjan Dey,
Sushant G. Ghosh,
Pankaj S. Joshi,
Kimet Jusufi,
Mohsen Khodadi,
Rahul Kumar Walia,
Ali Övgün,
Cosimo Bambi
Abstract:
Horizon-scale images of black holes (BHs) and their shadows have opened an unprecedented window onto tests of gravity and fundamental physics in the strong-field regime. We consider a wide range of well-motivated deviations from classical General Relativity (GR) BH solutions, and constrain them using the Event Horizon Telescope (EHT) observations of Sagittarius A$^*$ (Sgr A$^*$), connecting the si…
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Horizon-scale images of black holes (BHs) and their shadows have opened an unprecedented window onto tests of gravity and fundamental physics in the strong-field regime. We consider a wide range of well-motivated deviations from classical General Relativity (GR) BH solutions, and constrain them using the Event Horizon Telescope (EHT) observations of Sagittarius A$^*$ (Sgr A$^*$), connecting the size of the bright ring of emission to that of the underlying BH shadow and exploiting high-precision measurements of Sgr A$^*$'s mass-to-distance ratio. The scenarios we consider, and whose fundamental parameters we constrain, include various regular BHs, string-inspired space-times, violations of the no-hair theorem driven by additional fields, alternative theories of gravity, novel fundamental physics frameworks, and BH mimickers including well-motivated wormhole and naked singularity space-times. We demonstrate that the EHT image of Sgr A$^*$ places particularly stringent constraints on models predicting a shadow size larger than that of a Schwarzschild BH of a given mass, with the resulting limits in some cases surpassing cosmological ones. Our results are among the first tests of fundamental physics from the shadow of Sgr A$^*$ and, while the latter appears to be in excellent agreement with the predictions of GR, we have shown that a number of well motivated alternative scenarios, including BH mimickers, are far from being ruled out at present.
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Submitted 26 May, 2023; v1 submitted 16 May, 2022;
originally announced May 2022.
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Chirality dependence of thermoelectric response in a thermal QCD medium
Authors:
Debarshi Dey,
Binoy Krishna Patra
Abstract:
The lifting of the degeneracy between L- and R-modes of massless flavors in a weakly magnetized thermal QCD medium leads to a novel phenomenon of chirality dependence of the thermoelectric tensor, whose diagonal and non-diagonal elements are the Seebeck and Hall-type Nernst coefficient, respectively. Both coefficients in L-mode have been found to be greater than their counterparts in R-mode, howev…
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The lifting of the degeneracy between L- and R-modes of massless flavors in a weakly magnetized thermal QCD medium leads to a novel phenomenon of chirality dependence of the thermoelectric tensor, whose diagonal and non-diagonal elements are the Seebeck and Hall-type Nernst coefficient, respectively. Both coefficients in L-mode have been found to be greater than their counterparts in R-mode, however the disparity is more pronounced in the Nernst coefficient. Another noteworthy observation is the impact of the dimensionality of temperature (T) profile on the Seebeck coefficient, wherein we find that the coefficient magnitude is significantly enhanced (one order of magnitude) in the 2-D setup, compared to a 1-D T profile. Further, the chiral dependent quasifermion masses constrain the range of magnetic field (B) and T in a manner so as to enforce the weak magnetic field (eB << T^2 ) condition.
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Submitted 13 April, 2022;
originally announced April 2022.
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Thermoelectric response of a weakly magnetized thermal QCD medium
Authors:
Debarshi Dey,
Binoy Krishna Patra
Abstract:
We estimate the thermoelectric response, namely, the Seebeck and Nernst coefficients of a hot and deconfined plasma of quarks and gluons, created post ultrarelativistic heavy ion collisions in the presence of a weak, homogeneous background magnetic field. We employ the kinetic theory framework, wherein we use the relativistic Boltzmann transport equation in the relaxation time approximation. In-me…
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We estimate the thermoelectric response, namely, the Seebeck and Nernst coefficients of a hot and deconfined plasma of quarks and gluons, created post ultrarelativistic heavy ion collisions in the presence of a weak, homogeneous background magnetic field. We employ the kinetic theory framework, wherein we use the relativistic Boltzmann transport equation in the relaxation time approximation. In-medium interactions are taken into account via the quasiparticle masses of the partons extracted from one loop perturbative thermal QCD. We calculate the individual and total Seebeck coefficients in 2 different approaches (1-D and 2-D formulations). In the 1-D analysis, we find that a larger current quark mass has an amplifying effect on the individual Seebeck coefficient in the presence of a weak magnetic field. The temperature sensitivities of the individual Seebeck coefficients increase with increase in the current mass of the quark species in the case of a weak magnetic field whereas the same records a decreasing trend in the presence of a strong magnetic field. The variation of individual and total Seebeck coefficients with temperature, chemical potential and background magnetic field are found to follow similar trends in both the approaches, viz. decrease in magnitude with increasing temperature and increase in magnitude with increase in chemical potential and magnetic field. We also calculate the individual and total Nernst coefficients (in 2-D formulation) which are found to decrease with both temperature and chemical potential and increase with the magnetic field. Further, we find that the sign of the Nernst coefficient is independent of the electric charge of the charge carrier of the medium.
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Submitted 28 October, 2021; v1 submitted 23 March, 2021;
originally announced March 2021.
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Seebeck effect in a thermal QCD medium in the presence of strong magnetic field
Authors:
Debarshi Dey,
Binoy Krishna Patra
Abstract:
The strongly interacting partonic medium created post ultrarelativistic heavy ion collision experiments exhibits a significant temperature-gradient between the central and peripheral regions of the collisions, which in turn, is capable of inducing an electric field in the medium; a phenomenon known as Seebeck effect. The effect is quantified by the magnitude of the induced electric field per unit…
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The strongly interacting partonic medium created post ultrarelativistic heavy ion collision experiments exhibits a significant temperature-gradient between the central and peripheral regions of the collisions, which in turn, is capable of inducing an electric field in the medium; a phenomenon known as Seebeck effect. The effect is quantified by the magnitude of the induced electric field per unit temperature-gradient - the Seebeck coefficient ($S$). We study the coefficient, $S$ in the relativistic Boltzmann transport equation in relaxation-time approximation, as a function of temperature ($T$) and chemical potential ($μ$), wherein we find that with current quark masses, the magnitude of $S$ for individual flavours as well as that for the medium as a whole decreases with $T$ and increases with $μ$, with the electric charge of the flavour deciding the sign of $S$. The emergence of a strong magnetic field ($B$) in the non-central collisions at heavy-ion collider experiments motivates us to study the effect of $B$ on Seebeck effect. The strong $B$ affects $S$ in multifold ways, via : a) modification of phase-space due to the dimensional reduction, b) dispersion relation in lowest Landau level (occupation probability), and c) relaxation-time. We find that a strong $B$ not only decreases the magnitudes of $S$'s of individual species, it also flips their signs. This leads to a faster reduction of the magnitude of $S$ of the medium than its counterpart at $B=0$. We then explore how the interactions among partons in perturbative thermal QCD in the quasiparticle framework affect Seebeck effect, where we find that even in strong B, there is no more a flip of the sign of $S$ for individual species and an enhancement of the magnitudes of $S$ of individual species as well as that of the medium, compared to current quark mass description at either $B=0$ or $B \neq 0$.
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Submitted 6 November, 2020; v1 submitted 7 April, 2020;
originally announced April 2020.