Showing 1–50 of 826 results for author: Ramos, A

Optimal Finite Interval Discrepancy via Binary Refinement

Authors: Arthur F. Ramos, David B. Hulak, Ruy J. G. B. de Queiroz

Abstract: DeLeo, Henderschedt, and Wells introduced a finite-horizon version of the classical de Bruijn--Erdos interval discrepancy problem. Starting from the unit interval, one repeatedly splits an existing interval into two until $n$ intervals are present, and one minimizes the largest ratio between the longest and shortest intervals over all intermediate partitions. They constructed the lex-merge strateg… ▽ More DeLeo, Henderschedt, and Wells introduced a finite-horizon version of the classical de Bruijn--Erdos interval discrepancy problem. Starting from the unit interval, one repeatedly splits an existing interval into two until $n$ intervals are present, and one minimizes the largest ratio between the longest and shortest intervals over all intermediate partitions. They constructed the lex-merge strategy, whose discrepancy is $2^{1-1/\lceil n/2\rceil}$, and conjectured that this value is optimal for every $n$. We prove the conjecture. More generally, we establish a sharp lower bound for arbitrary binary refinement processes of positive masses: any process that starts with one positive mass, repeatedly replaces one mass by two positive masses with the same total, and terminates with $n$ masses must at some stage have largest-to-smallest ratio at least $2^{1-1/\lceil n/2\rceil}$. The proof tracks the minimum mass under refinement and uses the forced survival of a piece near the midpoint of the process. We also record the corresponding universal lower bound for $r$-ary refinements. △ Less

Submitted 8 August, 2026; originally announced August 2026.

Comments: 6 pages; Isabelle/HOL formalization available at https://doi.org/10.5281/zenodo.21856255

Black bounce sourced by non-minimally coupled linear electrodynamics and a canonical scalar field through a thin shell at the throat

Authors: Ednaldo L. B. Junior, José Tarciso S. S. Junior, Francisco S. N. Lobo, Gonzalo J. Olmo, Jorde A. A. Ramos, Manuel E. Rodrigues, Luís F. Dias da Silva, Henrique A. Vieira

Abstract: We construct a novel class of black bounce solutions within General Relativity, sourced by a canonical scalar field non-minimally coupled to linear electrodynamics, establishing a self-consistent framework in which regular black holes and traversable wormholes are supported by ordinary bulk matter, with the necessary exoticity confined to an infinitesimally thin defect at the bounce. We construct a novel class of black bounce solutions within General Relativity, sourced by a canonical scalar field non-minimally coupled to linear electrodynamics, establishing a self-consistent framework in which regular black holes and traversable wormholes are supported by ordinary bulk matter, with the necessary exoticity confined to an infinitesimally thin defect at the bounce. △ Less

Submitted 8 August, 2026; originally announced August 2026.

Comments: 19 pages, 7 figures

Topological Semantics for Scoped Computational Paths

Authors: Arthur Freitas Ramos, Ruy J. G. B. de Queiroz, Anjolina Grisi de Oliveira, Tiago M. L. de Veras

Abstract: Computational paths record equality as explicit finite traces of primitive steps. We give a topological semantics for a scoped rewrite presentation whose steps have continuous geometric realizations and whose named rewrites carry endpoint-fixed homotopies. For every presentation we construct a quotient arrow space with a canonical final-domain groupoid structure: multiplication is continuous on… ▽ More Computational paths record equality as explicit finite traces of primitive steps. We give a topological semantics for a scoped rewrite presentation whose steps have continuous geometric realizations and whose named rewrites carry endpoint-fixed homotopies. For every presentation we construct a quotient arrow space with a canonical final-domain groupoid structure: multiplication is continuous on the quotient of explicitly composable representatives. We prove an exact four-way criterion for this final composable topology to agree with the ordinary pullback topology, together with a compact-Hausdorff sufficient condition. Thus the unconditional construction exposes, rather than hides, the product-quotient issue in ordinary topological groupoids. The realization map to geometric homotopy classes is a continuous groupoid morphism and is faithful exactly under a separate geometric-completeness condition. In the universal presentation, a continuous section identifies the coherent-path quotient homeomorphically with the usual quotient-topologized fundamental groupoid. We then give finite-generator circle and genuine torus examples, with winding-based normal forms and classifications by Z and Z^2. A Lean 4.24.0 development checks the theorem package; the mathematical presentation is independent of the implementation. △ Less

Submitted 14 August, 2026; v1 submitted 4 August, 2026; originally announced August 2026.

Comments: 30 pages, 1 figure, 1 table. Lean artifact: https://github.com/Arthur742Ramos/ComputationalPathsLean (tag topological-paper-v12); Zenodo: https://doi.org/10.5281/zenodo.21938980

Properties of the $D_{s0}^*(2317)^\pm$ in hot and dense nuclear matter

Authors: Tomona Kinugawa, Àngels Ramos, Laura Tolos

Abstract: We investigate the properties of the $D_{s0}^\ast(2317)^\pm$ in hot and dense nuclear matter using a coupled-channel molecular model built on next-to-leading-order heavy meson chiral perturbation theory. In-medium modifications to the $D_{s0}^\ast(2317)^+$ stem from changes to the $DK$ channel within the coupled $DK$-$D_s η$ system. As nuclear density increases, the $D_{s0}^\ast(2317)^+$ quasipart… ▽ More We investigate the properties of the $D_{s0}^\ast(2317)^\pm$ in hot and dense nuclear matter using a coupled-channel molecular model built on next-to-leading-order heavy meson chiral perturbation theory. In-medium modifications to the $D_{s0}^\ast(2317)^+$ stem from changes to the $DK$ channel within the coupled $DK$-$D_s η$ system. As nuclear density increases, the $D_{s0}^\ast(2317)^+$ quasiparticle peak shifts toward lower energies and broadens, tracking the behavior of the $D$-meson spectral function. As for temperature effects, those are milder, with the thermal smearing of the Fermi surface and the melting of $Σ_c N^{-1}$ excitations in the $D$-meson spectral function shifting the $D_{s0}^\ast(2317)^+$ peak back toward its free-space mass while narrowing it. Conversely, the behavior of the $D_{s0}^\ast(2317)^-$ is governed by the $\bar D \bar K$ channel and its medium behavior is driven by the $\bar K$ spectral function. With increasing temperature, the $D_{s0}^\ast(2317)^-$ also approaches its free-space mass, but its width broadens before saturating at high temperatures. Incorporating explicit medium dependencies into the interaction kernel, driven by density and/or temperature variations in the pion decay constant, further shifts the $D_{s0}^\ast(2317)^+$ mass lower and narrows its width with temperature. As for $D_{s0}^\ast(2317)^-$, its mass also drops with temperature but its width increases. These contrasting medium behaviors offer a promising pathway to constrain the internal structure of these exotic states. △ Less

Submitted 2 August, 2026; originally announced August 2026.

Comments: 16 pages, 10 figures

Convex order, log-convexity and moments of averages of random variables

Authors: Felipe Gonçalves, José Madrid, Antonio Pedro Ramos

Abstract: We establish a convex order comparison for products of averages of exchangeable nonnegative random variables. As a consequence, we solve a conjecture of Lamkin and Tkocz (2022) on the log-convexity of moments of sample means, as well as its pointwise version, in a more general form involving arbitrary integer partitions. We establish a convex order comparison for products of averages of exchangeable nonnegative random variables. As a consequence, we solve a conjecture of Lamkin and Tkocz (2022) on the log-convexity of moments of sample means, as well as its pointwise version, in a more general form involving arbitrary integer partitions. △ Less

Submitted 1 August, 2026; originally announced August 2026.

Comments: 6 pages

MSC Class: 60E15; 26D15; 05A20

Focal-Plane Diagnostics of Atmospheric and Dome-Induced Turbulence: Exploring techniques and applications

Authors: Begoña García-Lorenzo, Seifeldin Abouelella, Kabir Baig, Zenaida García Rodríguez, Kshitij Ghimire, Moisés Pulido Torres, Alejandro Trujillo Ramos, Jose A. Acosta-Pulido, Julio A. Castro-Almazán, Donaji Esparza-Arredondo, Antonio Eff-Darwich

Abstract: Atmospheric turbulence remains the dominant source of image degradation in ground-based astronomy. Its impact depends not only on the integrated turbulence strength but also on the wavefront spatial-coherence outer scale (\LO) and on turbulence generated within the telescope enclosure (dome seeing). While seeing, coherence time, and related parameters are routinely monitored at major observatories… ▽ More Atmospheric turbulence remains the dominant source of image degradation in ground-based astronomy. Its impact depends not only on the integrated turbulence strength but also on the wavefront spatial-coherence outer scale (\LO) and on turbulence generated within the telescope enclosure (dome seeing). While seeing, coherence time, and related parameters are routinely monitored at major observatories, measurements of \LO\ and dome-induced turbulence remain sparse, limiting our ability to predict image quality and to construct accurate point-spread function (PSF) models. Building on methodology recently developed for seeing-limited integral-field spectroscopic (IFS) data, we present a series of complementary studies showing how spatial information encoded in standard observations can be used to diagnose both atmospheric and dome turbulence. We investigate the feasibility of extending these techniques beyond IFS observations to other seeing-limited instruments through the analysis of wavelength-dependent spatial profiles. We also present the development of data-driven three-dimensional PSF models based on atmospheric statistics for the reconstruction of seeing-limited IFS observations. These results show that widely available seeing-limited scientific observations, both from archival data and routine observatory operations, can provide meaningful and operationally useful constraints on key turbulence parameters and on the spectral behavior of dome seeing, complementing dedicated site-testing instrumentation. The resulting turbulence diagnostics have direct applications to PSF modelling, image reconstruction, image-quality prediction, and the optimization of future ELT operations. △ Less

Submitted 30 July, 2026; originally announced July 2026.

Comments: 14 pages, 7 Figures, SPIE Astronomical Telescopes + Instrumentation 2026, Paper 14150-252

TLA+-Bench: An Execution-Grounded Benchmark and Dataset for Natural-Language to TLA Specification Generation

Authors: Arslan Bisharat, Eric Spencer, Brian Ortiz, Khushboo Bhadauria, Mujtaba Nazari, Beatriz Santos, Anisa Ramos, TaiNing Wang, George K. Thiruvathukal, Konstantin Läufer, Mohammed Abuhamad

Abstract: Large language models increasingly write TLA$^{+}$ formal specifications from natural-language descriptions, but progress is hard to measure: existing resources grade by resemblance to a reference or by whether the output parses, neither of which shows correctness. We present TLA$^{+}$-Bench, a dataset and benchmark that grades by execution. Every gold specification ships a configuration the TLA… ▽ More Large language models increasingly write TLA$^{+}$ formal specifications from natural-language descriptions, but progress is hard to measure: existing resources grade by resemblance to a reference or by whether the output parses, neither of which shows correctness. We present TLA$^{+}$-Bench, a dataset and benchmark that grades by execution. Every gold specification ships a configuration the TLA$^{+}$ model checker runs over the full reachable state space, deciding exactly whether the specification holds the properties that configuration names. The dataset holds 403 model-checked gold and 897 parse-only silver specifications from 13 public repositories, subsumes prior TLA$^{+}$ generation data, and carries four model-written descriptions in two styles from two providers, with difficulty and category labels. Our main finding is about measurement itself: an exact oracle gives not one correctness number but a range. Varying only the grading choices earlier benchmarks leave unstated, on one fixed set of model outputs, the correct rate moves sixfold, from 10.0\% to 1.7\%; adding the interface-supply choice, where the model is told the configuration's names, widens the range to elevenfold, from 18.7\% to 1.7\%. We call this range the correctness envelope and measure each of its bounds. The findings inside it are stable. Every model writes valid TLA$^{+}$ far more often than correct TLA$^{+}$: the strongest is correct 16\% of the time by default and 26\% when given the interface names, open models at most 1\%, and correctness falls sharply with difficulty. △ Less

Submitted 25 July, 2026; originally announced July 2026.

Comments: 17 pages, appendix included. Introduces TLA+-Bench, an execution-grounded benchmark and dataset for natural-language to TLA$^{+}$ specification generation. Dataset, evaluation code, and model outputs available at publication

Multiplier obstructions for Legendre pairs of length 333

Authors: Arthur F. Ramos, David B. Hulak, Ruy J. G. B. de Queiroz

Abstract: A Legendre pair of length 333 would yield a Hadamard matrix of order 668, the smallest order presently unresolved by the Hadamard conjecture. We study the structured case in which both sequences are fixed by a common subgroup $H\leq(\mathbb Z/333\mathbb Z)^\times$ acting by coordinate multiplication. We prove that such a pair can exist only when $|H|\leq 6$. After a mod-3 compression reduces the p… ▽ More A Legendre pair of length 333 would yield a Hadamard matrix of order 668, the smallest order presently unresolved by the Hadamard conjecture. We study the structured case in which both sequences are fixed by a common subgroup $H\leq(\mathbb Z/333\mathbb Z)^\times$ acting by coordinate multiplication. We prove that such a pair can exist only when $|H|\leq 6$. After a mod-3 compression reduces the problem to an order-108 kernel, there are exactly 30 subgroups. We exclude 21 of them, including all 19 subgroups of order at least 9. The final order-9 subgroup is eliminated analytically: its orbit structure restricts the 9-compressed entries to $\{\pm1,\pm17,\pm19,\pm35,\pm37\}$; the Legendre equations force a $+17,-17$ pair in one compressed sequence, and a single-shift autocorrelation bound then contradicts the required compressed correlation. The remaining exclusions use full-image compression, a row-sum congruence, exact meet-in-the-middle enumeration, and proof-carrying pseudo-Boolean encodings. The solver-assisted cases are accompanied by independently checked DRAT proofs or direct arithmetic certificates. The result constrains fixed common-multiplier symmetry only; the unrestricted existence problems remain open. △ Less

Submitted 22 July, 2026; originally announced July 2026.

Comments: 12 pages, 3 tables

MSC Class: 05B20 (primary); 05B10; 11B83 (secondary)

How large can galaxies be? Ultra-deep imaging of IC 1101, the most extended known galaxy

Authors: Carlos Marrero-de la Rosa, Ignacio Trujillo, Ignacio Ruiz Cejudo, Mireia Montes, Fernando Buitrago, Giulia Golini, Sergio Guerra Arencibia, Andrés Asensio Ramos, Raúl Infante-Sainz, Adriana de Lorenzo-Cáceres, Jairo Méndez-Abreu, Samane Raji, Javier Román, Manuel Sánchez-Benavente, Zahra Sharbaf

Abstract: The maximum physical extent that galaxies can reach is poorly understood. In this regard, IC 1101, one of the most extended and massive galaxies known, provides a valuable opportunity to constrain the upper limit of galaxy sizes at the present epoch. Previous deep imaging of the system confirmed its enormous extension, but did not indicate whether it has an edge. We explore this issue using the de… ▽ More The maximum physical extent that galaxies can reach is poorly understood. In this regard, IC 1101, one of the most extended and massive galaxies known, provides a valuable opportunity to constrain the upper limit of galaxy sizes at the present epoch. Previous deep imaging of the system confirmed its enormous extension, but did not indicate whether it has an edge. We explore this issue using the deepest images ever taken of this galaxy; ultra-deep g- and r- band imaging from the INT/WFC, reaching μ = 30 mag arcsec^-2 (3σ in an area equivalent to 10 x 10 arcsec^2). We model and subtract the scattered light from both stars and the galaxy itself using an extended PSF characterization and a hybrid wavelet-based deconvolution. Using a combination of surface brightness, colour, and stellar mass density profiles oriented at different position angles, we find that the main body of IC 1101 extends to Redge = 260 kpc along the semi-major axis (assuming the redshift of Abell 2029, z = 0.077), enclosing 3.4 x 10^12 M_sun in stars. This Redge is among the largest edge radii measured for any galaxy to date, placing IC 1101 at the extreme upper end of the mass-size relation. In addition, we report a large number of asymmetrical, very low surface brightness features around the galaxy that are spatially consistent with the large-scale disturbances observed in the intracluster medium through X-ray studies of the Abell 2029 cluster, in which IC 1101 is embedded. With a confirmed diameter of around 520 kpc, IC 1101 stands as the largest galaxy known to date; yet, its outskirts show clear signatures of ongoing mass assembly, indicating that its spatial extent is still growing. △ Less

Submitted 11 August, 2026; v1 submitted 16 July, 2026; originally announced July 2026.

Comments: 20 pages, 15 figures. Accepted for publication in Astronomy and Astrophysics. Corrected typos

Influence of compaction pressure on the impedance of Gadolinium Doped Ceria electrolytes for IT-SOFCs

Authors: Renato A. N. de Oliveira, Celeste Z. A. Aquino, Magna Monteiro Schaerer, Rafael Galiza Yoshimura, Liliana Mogni, Maurico Arce, Diego G. Lamas, Lucia Toscani, Maria Belén Arcentales Vera, Esteban Elvis Asto Ramos, Marcia Carvalho de Abreu Fantini, Taofeeq Oladayo Bello, Tereza da Silva Martins, Danilo Waismann Losito, James Moraes de Almeida, Valeria Spolon Marangoni, Leopoldo Suescunand, Santiago Figueroa

Abstract: Gadolinium doped ceria (GDC) is one promising oxygen-ion conducting ceramic electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs), due to its high ionic conductivity at reduced operating temperatures, favorable defect chemistry, and compatibility with a broad range of electrode materials [1,2]. Despite extensive understanding of its intrinsic ion transport mechanisms, the infl… ▽ More Gadolinium doped ceria (GDC) is one promising oxygen-ion conducting ceramic electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs), due to its high ionic conductivity at reduced operating temperatures, favorable defect chemistry, and compatibility with a broad range of electrode materials [1,2]. Despite extensive understanding of its intrinsic ion transport mechanisms, the influence of ceramic processing parameters on the effective electrical behavior of polycrystalline GDC electrolytes remains an active topic for investigation [3-5]. In particular, processing steps that govern green body formation and sintering can strongly affect microstructural features such as density, grain size, grain boundary character, and residual porosity, which in turn determine the macroscopic conductivity [4-6]. In this work, dense GDC ceramic pellets were fabricated under systematically varied isostatic compaction pressures ranging from 49 to 140 MPa, followed by sintering at 1350 C for four hours under identical thermal conditions. Platinum electrodes were deposited on both sides of the pellets by electron-beam deposition, and the electrical properties were characterized by electrochemical impedance spectroscopy (EIS) over a wide temperature range. The results demonstrate a dependence of the impedance with respect to compaction pressure. △ Less

Submitted 15 July, 2026; v1 submitted 14 July, 2026; originally announced July 2026.

From Rules to Nash Equilibria: A Lean 4 Case Study in Game-Theoretic Analysis of a Competitive Trading Card Game

Authors: Arthur F. Ramos, Tulio Soria

Abstract: We present a metagame analysis of the competitive Pokemon Trading Card Game, machine-checked in Lean 4 over real tournament data. The headline game-theoretic results, including Nash equilibrium, replicator dynamics, and the matrix-level type-bridge computation, rely on native_decide, which trusts Lean's compiler rather than its kernel; the trust boundary is made explicit. The artifact spans approx… ▽ More We present a metagame analysis of the competitive Pokemon Trading Card Game, machine-checked in Lean 4 over real tournament data. The headline game-theoretic results, including Nash equilibrium, replicator dynamics, and the matrix-level type-bridge computation, rely on native_decide, which trusts Lean's compiler rather than its kernel; the trust boundary is made explicit. The artifact spans approximately 31,900 lines, 87 files, and 2,627 theorems, of which roughly 200 directly verify empirical claims, with no sorry, admit, or custom axioms. Analyzing Trainer Hill data from January to February 2026 for events with at least 50 players, over 14 archetypes and their full pairwise matchup matrix, we prove a popularity paradox: the most played deck, Dragapult, with 15.5% metagame share, has only 46.7% expected win rate, while Grimmsnarl, with 5.1% share, achieves 52.7%. A machine-checked Nash equilibrium of the raw game assigns Dragapult 0% weight; exhaustive enumeration over all nonempty support subsets confirms a unique symmetric Nash equilibrium of the constant-sum symmetrization with seven-deck support. Against this equilibrium mix, Dragapult falls 40.4 permil below the game value. Single-step replicator dynamics indicate downward fitness pressure on Dragapult, upward pressure on Grimmsnarl, and strongest extinction pressure on Alakazam. A 10,000-iteration sensitivity analysis confirms qualitative stability, with core support decks appearing in more than 96% of resampled equilibria. The primary contribution is methodological: a reproducible case study showing how formal verification can turn qualitative metagame narratives into machine-checkable, re-runnable strategic science. △ Less

Submitted 9 July, 2026; originally announced July 2026.

Comments: 13 pages, 3 figures, 10 tables. Lean 4 artifact with 87 files, approximately 31,900 lines, and 2,627 theorems; no sorry, admit, or custom axioms

Kaon-deuteron correlation function from an effective field theory approach

Authors: Juan Torres-Rincon, Àngels Ramos

Abstract: We present a study of femtoscopic correlation functions for $K^{-}d$ and $K^{+}d$ pairs, and compare our results with recent measurements by the ALICE Collaboration in both Pb-Pb and high-multiplicity $pp$ collisions. The kaon-deuteron wave functions are derived from scattering amplitudes using a unitarized chiral effective theory model describing the elementary interactions of $K^{\pm}$ mesons wi… ▽ More We present a study of femtoscopic correlation functions for $K^{-}d$ and $K^{+}d$ pairs, and compare our results with recent measurements by the ALICE Collaboration in both Pb-Pb and high-multiplicity $pp$ collisions. The kaon-deuteron wave functions are derived from scattering amplitudes using a unitarized chiral effective theory model describing the elementary interactions of $K^{\pm}$ mesons with nucleons. We then evaluate the $K^{\pm}d$ strong scattering amplitudes by solving the Faddeev equations within two distinct frameworks: the Impulse Approximation and the Fixed Center Approximation, which accounts for multiple scatterings. We also incorporate the long-range Coulomb effects between the kaon and the deuteron. We show that the $K^{-}d$ correlation function exhibits large sensitivity to both the size of the emitting source and the relative momentum of the pair, being heavily influenced by rescattering processes. In contrast, the $K^{+}d$ correlation function is dominated by the weakly repulsive $K^{+}N$ interaction, showing deviations from purely Coulombic behavior only at small emission source sizes. Our predictions are in agreement with the ALICE experimental data, and also with the energy-shift and width of the $1s$ level of the kaonic deuterium preliminary results from the SIDDHARTA 2 Collaboration. △ Less

Submitted 7 July, 2026; originally announced July 2026.

Comments: 8 pages, 2 figures. Presented by Juan Torres-Rincon at the Excited QCD 2026 Workshop in Granada (Spain), on January 10, 2026. To be published in Acta Physica Polonica B

Evolution of Chemistry in the envelope of HOt corinoS (ECHOS). III. Sulphur chemistry in the Class 0 objects HH 212 and NGC 1333 IRAS 4A

Authors: P. Fernández-Ruiz, A. Fuente, G. Esplugues, D. Navarro-Almaida, P. Riviére-Marichalar, T. Alonso-Albi, M. Rodríguez-Baras, A. Asensio Ramos, C. Westendorp Plaza, L. Moral-Almansa

Abstract: Our goal is to find chemical diagnostics to determine the physical conditions in protostellar envelopes and help establish the development of matter during the formation of a low-mass star, as well as investigating a possible variation of sulphur depletion during the star formation process at the scale of the cold envelope. With observations with the Yebes-40m and IRAM-30m telescopes, we estimate… ▽ More Our goal is to find chemical diagnostics to determine the physical conditions in protostellar envelopes and help establish the development of matter during the formation of a low-mass star, as well as investigating a possible variation of sulphur depletion during the star formation process at the scale of the cold envelope. With observations with the Yebes-40m and IRAM-30m telescopes, we estimate column densities of sulphur-bearing species in the Class 0 objects HH212 and NGC1333 IRAS4A. A neural emulator of the chemical code Nautilus is used to constrain the chemical time, density, gas temperature, cosmic ray ionization rate, and sulphur elemental abundance in the cold envelope of these objects. We compare the resulting abundances of these species with those towards the Class 0 object B335. While sulphur-bearing species containing carbon chains are between 3 and 7 times more abundant in B335 than in the other two objects, sulphur oxides and nitrogen-bearing species are 3 times more abundant in NGC1333 IRAS4A. Our chemical modelling shows that, while the chemistry of HH212 and NGC1333 IRAS4A is well reproduced considering a gas temperature of 25 K and a sulphur depletion of a factor of 100 in their envelopes, significant differences are found in their average density and cosmic ray ionization rate. Comparing with similar studies in pre-stellar and protostellar cores, we derive an increase in the SO/CS and SO$_2$/C$_2$S ratios of about two orders of magnitude and a potential decrease in the HCS$^+$/CS ratio of a factor of 10 in the transition from the pre-stellar to the Class 0 phase. Sulphur compounds are good evolutionary tracers of the pre- to protostellar phase transition, with oxygen-bearing species being more abundant than those containing carbon in the evolved sources. Nonetheless, sulphur depletion in the cold envelope of Class 0 objects remains similar to that in starless cores. △ Less

Submitted 1 July, 2026; originally announced July 2026.

Comments: 23 pages, 17 figures. Accepted for publication in A&A

Black bounce solutions in a realistic dark matter halo from M60*

Authors: Ednaldo L. B. Junior, José Tarciso S. S. Junior, Francisco S. N. Lobo, Jorde A. A. Ramos, Manuel E. Rodrigues, Diego Rubiera-Garcia, Luís F. Dias da Silva, Henrique A. Vieira

Abstract: We formulate a Simpson-Visser black bounce solution embedded in a dark matter halo. The latter is modeled using an empirical density profile calibrated from observations of the elliptical galaxy NGC 4649 (M60), based on imaging from the Hubble Space Telescope, stellar velocity dispersion data, and the dynamics of globular clusters. The resulting spacetime metric, in addition to retaining dependenc… ▽ More We formulate a Simpson-Visser black bounce solution embedded in a dark matter halo. The latter is modeled using an empirical density profile calibrated from observations of the elliptical galaxy NGC 4649 (M60), based on imaging from the Hubble Space Telescope, stellar velocity dispersion data, and the dynamics of globular clusters. The resulting spacetime metric, in addition to retaining dependence on the mass parameter $m$, the asymptotic circular velocity $V_c$, and the halo scale radius $a$, also depends on the regularization parameter $q_H$. It reduces to the canonical black bounce solution without a halo in the limit $V_c\to0$ (or $a\to\infty$), and to the Schwarzschild solution with a dark matter halo when $q_H\to0$. We analyze the response of fundamental geometrical and physical quantities in the presence of a halo, such as the event horizon radius, the shadow size, and some curvature invariants. In particular, we show the observational range of the shadow radius, from the imaging of Sagittarius A*, constrains the parameter space of the solution to regular black hole configurations, excluding wormhole scenarios. We study the dynamics of massless particles here through the effective potential and examine thermodynamic properties, highlighting the impact on thermodynamic potentials in terms of entropy. Finally, we extend the analysis to scenarios with electromagnetic fields non-minimally coupled to a phantom scalar field, considering configurations with either purely magnetic or purely electric charge. Our results suggest that the dark matter halo influences both the internal geometry and the observational properties of black bounces, imposing constraints on the solution's parameter space from astrophysical data. This highlights the need to include astrophysical environments in modeling regular black holes and wormholes, offering new tests of gravity in the strong-field regime. △ Less

Submitted 19 June, 2026; originally announced June 2026.

Comments: 23 pages, 17 figures,

Toward in-situ/operando X-ray absorption spectroscopy and electrochemical characterization of solid oxide fuel cells

Authors: Renato A. N. de Oliveira, Rafael Galiza Yoshimura, Liliana Mogni, Maurico Arce, Diego G. Lamas, Lucia Toscani, Maria Belén Arcentales Vera, Esteban Elvis Asto Ramos, Magna Monteiro Schaerer, Celeste Z. A. Aquino, Marcia Carvalho de Abreu Fantini, Taofeeq Oladayo Bello, Tereza da Silva Martins, Danilo Waismann Losito, James Moraes de Almeida, Valeria Spolon Marangoni, Leopoldo Suescunand, Santiago Figueroa

Abstract: The focus of the present work is the development of specialized experimental instrumentation compatible with synchrotron characterization for in-situ and operando symmetric intermediate temperature solid oxide fuel cells (IT-SOFC) studies at maximum temperatures of 800 C , exposed to reducing and oxidizing atmospheres, using fluorescence X-ray absorption spectroscopy (XAS) measurements in combinat… ▽ More The focus of the present work is the development of specialized experimental instrumentation compatible with synchrotron characterization for in-situ and operando symmetric intermediate temperature solid oxide fuel cells (IT-SOFC) studies at maximum temperatures of 800 C , exposed to reducing and oxidizing atmospheres, using fluorescence X-ray absorption spectroscopy (XAS) measurements in combination with electrochemical impedance spectroscopy (EIS) in the multipurpose Quati beamline at CNPEM/SIRIUS synchrotron facility [1]. Symmetric IT-SOFC are gaining importance due to their structural simplicity, as they allow for the use of identical materials on both sides of the fuel cell electrolyte; the anode, and the cathode [ 2,3 ]. The symmetric configuration opens new opportunities for fundamental research of electrode materials and improves the versatility of SOFC electrochemical devices [2,3]. △ Less

Submitted 22 June, 2026; originally announced June 2026.

Comments: no comments

Shear-Induced Electrophoretic Migration Perpendicular to the Electric Field

Authors: Andrés Rodríguez-Galán, Raúl Fernández-Mateo, Pablo García-Sánchez, Antonio Ramos

Abstract: Recent experiments combining electrophoresis with pressure-driven flows in microchannels have revealed that microparticles undergo lateral migration perpendicular to the applied electric field. Although fluid inertia has been proposed as a possible explanation, inertial effects are negligibly small in these regimes, leaving the underlying physical mechanism an open question. In this study, we addr… ▽ More Recent experiments combining electrophoresis with pressure-driven flows in microchannels have revealed that microparticles undergo lateral migration perpendicular to the applied electric field. Although fluid inertia has been proposed as a possible explanation, inertial effects are negligibly small in these regimes, leaving the underlying physical mechanism an open question. In this study, we address these observations by extending previous theoretical work on concentration polarization,i.e., the external-field-induced modification of the ionic concentration field surrounding a dielectric object. We consider a dielectric particle with surface conductance subjected simultaneously to an external electric field and a shear flow. We show that the shear flow breaks the symmetry of the ionic concentration around the particle in the direction perpendicular to the applied field, thereby driving lateral migration. We demonstrate that the resulting migration velocity comprises two distinct contributions: an electrophoretic and a diffusiophoretic component. Our theory yields an explicit expression for the velocity magnitude as a function of the zeta potential and the Dukhin number, predicting typical speeds on the order of $\mathrmμ$m/s for representative experimental parameters. Notably, the model also predicts a reversal in the migration direction for Dukhin numbers of order unity. △ Less

Submitted 18 June, 2026; originally announced June 2026.

Comments: 11 pages. Article and Supplementary Material

3DSTokesFlow: simulation-based inference for 3D Stokes profiles using flow matching

Authors: A. Asensio Ramos, K. E. Yang, M. J. Martinez Gonzalez, S. Curt Dodds, X. Sun

Abstract: The standard interpretation of observed Stokes profiles to infer the physical conditions of the solar atmosphere is inherently an ill-defined problem due to observational noise and mathematical degeneracies. Traditional pixel-by-pixel (1D) inversion codes provide point estimates with unreliable uncertainties, at the expense of significant computational time. Recent machine-learning-based Bayesian… ▽ More The standard interpretation of observed Stokes profiles to infer the physical conditions of the solar atmosphere is inherently an ill-defined problem due to observational noise and mathematical degeneracies. Traditional pixel-by-pixel (1D) inversion codes provide point estimates with unreliable uncertainties, at the expense of significant computational time. Recent machine-learning-based Bayesian frameworks are restricted to 1D spatial configurations, ignoring crucial spatial correlations between neighboring pixels. We aim to develop a novel multidimensional inversion framework capable of performing fast and scalable Bayesian inference across an entire 2D field-of-view (FoV). This approach seeks to provide accurate height-dependent atmospheric parameters with reliable posterior distributions while exploiting spatial correlations. We introduce a new generative modeling strategy based on conditional flow matching. The model utilizes multi-scale spatial features extracted from observed Stokes profiles in the Fe I line pair at 630 nm, which then conditions a flow matching generative model to sample from the complex posterior distribution of the atmospheric parameters. The framework is trained using realistic 3D quiet Sun magnetohydrodynamic simulations. Validation on independent synthetic datasets demonstrates that the model accurately captures the true 3D stratification of all thermodynamic and magnetic parameters. Because the code additionally provides a geometrical height scale, it allows for the computation of 3D electric current density maps, Lorentz forces, and Ohmic and ambipolar dissipation maps in the solar photosphere. Application to real Hinode/SP quiet Sun observations yields highly localized electric currents at magnetic boundaries. We also leverage the 3D geometrical information to trace the emergence of small-scale emerging magnetic loops across the solar atmosphere. △ Less

Submitted 11 June, 2026; originally announced June 2026.

Comments: 15 pages, 12 figures, 1 appendix, submitted to A&A

Detection of the distant quasar OP 313 with the first Large-Sized Telescope of CTAO

Authors: K. Abe, S. Abe, J. Abhir, A. Abhishek, V. A. Acciari, F. Acero, A. Aguasca-Cabot, I. Agudo, C. Alispach, D. Ambrosino, T. Aniello, S. Ansoldi, L. A. Antonelli, C. Aramo, A. Arbet-Engels, C. Arcaro, T. T. H. Arnesen, K. Asano, P. Aubert, A. Babić, C. Bakshi, A. Baktash, M. Balbo, A. Bamba, A. Baquero Larriva , et al. (391 additional authors not shown)

Abstract: In December 2023, the Large-Sized Telescope prototype (LST-1) detected for the first time VHE $γ$-ray emission from the FSRQ OP~313 becoming the furthest blazar ever observed at VHE with z=0.997. We aim to characterize the $γ$-ray emission of OP 313 during this flare, comparing it with its average emission state in order to understand the processes leading to this detection. Its remarkable distanc… ▽ More In December 2023, the Large-Sized Telescope prototype (LST-1) detected for the first time VHE $γ$-ray emission from the FSRQ OP~313 becoming the furthest blazar ever observed at VHE with z=0.997. We aim to characterize the $γ$-ray emission of OP 313 during this flare, comparing it with its average emission state in order to understand the processes leading to this detection. Its remarkable distance also enables studies on the Extragalactic Background Light (EBL), with the goal of evaluating the attenuation of VHE $γ$-ray photons. We characterize the $γ$-ray emission during the flare in December 2023 and the low emission state observed in January 2024 thanks to the LST-1 and MAGIC data and quasi-simultaneous \textit{Fermi}-LAT observations. This dataset also enables us to evaluate the EBL attenuation by systematically exploring the EBL intensity over the $γ$-ray spectrum. Finally, we study the multi-wavelength emission and interpret the broadband spectral energy distribution (SED) within blazar radiative models including the thermal contributions from the accretion disc, dusty torus and broad line region. We also characterize the flare brightness in the high-energy (HE, $E>100$~MeV) $γ$-ray band, that was found to be a factor 50 above the average emission seen by \textit{Fermi}-LAT. The HE and VHE observations allow us to set constrains to the EBL density. Finally, thanks to the extensive multi-wavelength campaign organized, we are able to construct and model the broadband SED of OP~313 within the framework of a two-zone leptonic model where the $γ$-ray emission is produced via inverse-Compton scattering of the broad line region, accretion disk and dusty torus photon fields. However the dominant external photon field remains unknown, as several combinations are able to successfully explain the $γ$-ray emission observed. △ Less

Submitted 26 May, 2026; originally announced May 2026.

Comments: 25 pages, 9 figures

Comprehensive study of hidden charm pentaquarks with an improved unitarization method

Authors: E. E. Garcia-Gonzales, V. K. Magas, A. Ramos

Abstract: This work investigates dynamically generated hidden-charm baryon resonances arising from meson-baryon interactions. Using the local hidden gauge formalism, we model the interaction via t-channel vector meson exchange and unitarize the amplitude using the Bethe-Salpeter equation. To address regularization issues, we propose a novel ``hybrid loop function'' scheme that eliminates the unphysical pole… ▽ More This work investigates dynamically generated hidden-charm baryon resonances arising from meson-baryon interactions. Using the local hidden gauge formalism, we model the interaction via t-channel vector meson exchange and unitarize the amplitude using the Bethe-Salpeter equation. To address regularization issues, we propose a novel ``hybrid loop function'' scheme that eliminates the unphysical poles -- common artifacts in cutoff or dimensional regularization -- while keeping the predictions of physical states. Consequently, the model successfully reproduces six experimentally known hidden-charm pentaquarks as well as earlier theoretical results, and predicts new states in the S=-1, I=1 sector. △ Less

Submitted 20 May, 2026; originally announced May 2026.

Comments: 25 pages, 17 figures, 12 tables

Witnessing the rapid growth of disk galaxies over cosmic time using JWST and HST

Authors: Samane Raji, Mireia Montes, Ignacio Trujillo, Fernando Buitrago, Carlos Marrero-de la Rosa, Andrés Asensio Ramos

Abstract: Measuring galaxy sizes is fundamental to understanding how galaxies grow and evolve. Traditional methods to measure sizes either trace the concentration of light (i.e., effective radius) or are limited by the depth of the survey (isophotal methods). With the advent of deep, wide surveys, a new physically motivated definition of size has emerged: the edge of the galaxy, defined as the most distant… ▽ More Measuring galaxy sizes is fundamental to understanding how galaxies grow and evolve. Traditional methods to measure sizes either trace the concentration of light (i.e., effective radius) or are limited by the depth of the survey (isophotal methods). With the advent of deep, wide surveys, a new physically motivated definition of size has emerged: the edge of the galaxy, defined as the most distant location where star formation has occurred or is still occurring. In this work, we take advantage of the extraordinary depth and spatial resolution of the Hubble and James Webb Space Telescopes to perform an accurate study of galaxy edges at $z=1$. Using 22 photometric bands, we derive radial age and metallicity profiles for two disk galaxies in the GOODS-South field with stellar masses of around $4\times10^{10}\ M_\odot$. The age profiles display a characteristic U-shape, while the metallicity profiles steadily decrease with galactocentric distance. The turnover in the age profile occurs near the galaxy edge, suggesting that stellar migration is responsible for the stars beyond the edge of these galaxies. Comparison with $z=0$ disk galaxies suggests that galaxies at $z=1$ grow inside-out, with little or no increase in mass within the inner 8 kpc, but a significant increase (approximately 300\%) in the outer regions. △ Less

Submitted 14 May, 2026; originally announced May 2026.

Comments: 17 pages, 5 figure. Accepted for publication in A&A. Comments are welcome. Samaneraji@gmail.com

Marginal multi-object multi-frame blind deconvolution

Authors: A. Asensio Ramos

Abstract: High-resolution ground-based solar imaging relies heavily on multi-object multi-frame blind deconvolution to correct for atmospheric turbulence. However, the traditional joint maximum likelihood estimation methods in which object and the atmospheric aberrations are estimated together face some problems. In this paper, we introduce a marginal estimator for the multi-object multi-frame blind deconvo… ▽ More High-resolution ground-based solar imaging relies heavily on multi-object multi-frame blind deconvolution to correct for atmospheric turbulence. However, the traditional joint maximum likelihood estimation methods in which object and the atmospheric aberrations are estimated together face some problems. In this paper, we introduce a marginal estimator for the multi-object multi-frame blind deconvolution problem. By employing a framework to marginalize over the observed objects, we develop a reconstruction method that offers several distinct advantages over joint estimation. First, the marginalization provides enhanced regularization that naturally accounts for object uncertainty, successfully preventing the reconstruction algorithm from erroneously assigning noise to high-order aberrations. Second, the marginal estimator yields more contrast control, as it is much less sensitive to the hyperparameters dictating the power spectral density (PSD) of the object. This robustness allows these hyperparameters to be optimized, enabling a ``plug-and-play'' deployment that removes the need for manual tuning. Finally, we demonstrate that the proposed method is accessible and simple to implement, requiring only the addition of a log-determinant term to the traditional merit function. With minimal modifications required for existing blind deconvolution pipelines, the estimator has been fully integrated into the open-source torchmfbd package for its use by the solar physics community. △ Less

Submitted 12 May, 2026; originally announced May 2026.

Comments: 22 pages, 6 figures, submitted to Solar Physics

Accelerating 3D Non-LTE Synthesis with Graph Neural Networks

Authors: A. Vicente Arévalo, A. Asensio Ramos, C. J. Díaz Baso

Abstract: Spectropolarimetric interpretation of chromospheric lines requires solving the radiative transfer problem under non-local thermodynamic equilibrium (non-LTE) conditions. This means computing atomic-level populations self-consistently with the radiation field. While traditional inversion codes employ 1.5D approximations, they neglect horizontal radiative transfer, which can be significant near magn… ▽ More Spectropolarimetric interpretation of chromospheric lines requires solving the radiative transfer problem under non-local thermodynamic equilibrium (non-LTE) conditions. This means computing atomic-level populations self-consistently with the radiation field. While traditional inversion codes employ 1.5D approximations, they neglect horizontal radiative transfer, which can be significant near magnetic structures and in the chromosphere. We present a method to solve 3D atomic-level populations using Graph Neural Networks (GNNs), extending prior 1.5D work to the full 3D domain. By discretizing the solar atmosphere as a directed graph, in which nodes encode physical properties and edges encode spatial distances, an Encode-Process-Decode GNN propagates information to efficiently capture radiative coupling. The network is trained on a Bifrost simulation using Ca II populations from Multi3D as ground truth. The trained GNN accurately predicts populations of the five-level Ca II atom plus continuum. Correlations exceed 0.99 in the photosphere and mid-chromosphere; errors in the upper chromosphere remain unbiased. Inference is $\sim 10^6$ times faster than traditional iterative solvers. Spectral synthesis of the Ca II 8542 Å line yields intensity profiles with $< 2 \%$ mean residuals relative to the full 3D solution. This framework bypasses the computational bottleneck of iterative solvers while preserving essential non-LTE physics, including horizontal transfer, paving the way toward routine 3D non-LTE inversions. △ Less

Submitted 10 May, 2026; originally announced May 2026.

Comments: Accepted for publication in A&A. 9 pages, 6 figures

Journal ref: A&A 710, A256 (2026)

Formalizing Singer Sidon Constructions and Sidon Set Infrastructure in Lean 4

Authors: David B. Hulak, Arthur F. Ramos, Ruy J. G. B. de Queiroz

Abstract: Erdős Problem 30 asks for sharp asymptotics of the Sidon extremal function $h(N)$, and Singer's construction is the classical source of lower-bound examples matching the main term. We present a Lean 4 formalization of Singer's Sidon set construction, together with reusable Sidon-set infrastructure for additive combinatorics. For every prime power $q=p^k$, we prove the existence of a Sidon set modu… ▽ More Erdős Problem 30 asks for sharp asymptotics of the Sidon extremal function $h(N)$, and Singer's construction is the classical source of lower-bound examples matching the main term. We present a Lean 4 formalization of Singer's Sidon set construction, together with reusable Sidon-set infrastructure for additive combinatorics. For every prime power $q=p^k$, we prove the existence of a Sidon set modulo $q^2+q+1$ of cardinality $q+1$; the prime-field case $q=p$ is the base presentation. The proof proceeds through a non-trivial algebraic chain: construction of the base field and its degree-three extension, analysis of the trace kernel as a 2-dimensional subspace over the base field, a geometric argument via subspace intersections establishing the multiplicative Sidon property in the quotient group, and a transfer from quotient multiplication to modular integer addition. Around this central result, we develop a reusable Sidon set library. It comprises interval and modular Sidon sets, the extremal function $h(N)$, Lindström's cross-difference inequality, a Johnson-route shift-incidence upper bound of the form $h(N)\leq\sqrt{N}+N^{1/4}+O(1)$, representation-function identities, and unconditional two-sided $h(N)=Θ(\sqrt{N})$ bounds with exact floor-rounded finite statements for $N\geq 5$. We further formalize a conditional reduction: subpolynomial prime gaps together with a full subpolynomial upper-error hypothesis for $h(N)$ imply the Erdős Problem 30 estimate $h(N)=\sqrt{N}+O_ε(N^ε)$ for every $ε>0$. The Singer/Sidon modules and transfer lemmas comprise 7,541 lines of Lean 4 with zero active uses of sorry. We describe the mathematical lessons learned, focusing on how formalization clarifies the precise scope of classical arguments and forces explicit treatment of the passage from the field-theoretic construction to integer Sidon predicates. △ Less

Submitted 12 May, 2026; v1 submitted 4 May, 2026; originally announced May 2026.

Comments: 25 pages, LaTeX; expanded from prime-field to prime-power Singer constructions; added the prime-power theorem and prime-power lower-bound reduction; exposition revised throughout

Certified Qualitative Analysis of the SIR ODE and Reusable Scalar Lemmas in Isabelle/HOL

Authors: David B. Hulak, Arthur F. Ramos, Ruy J. G. B. de Queiroz

Abstract: We present a mechanically checked Isabelle/HOL bridge from the Picard-Lindelof flow infrastructure in the Archive of Formal Proofs (AFP) to selected qualitative facts for the mass-action, closed-population SIR epidemic ODE. The epidemiological facts are classical; the contribution is reusable theorem infrastructure connecting the AFP local-flow construction to global forward existence, uniqueness,… ▽ More We present a mechanically checked Isabelle/HOL bridge from the Picard-Lindelof flow infrastructure in the Archive of Formal Proofs (AFP) to selected qualitative facts for the mass-action, closed-population SIR epidemic ODE. The epidemiological facts are classical; the contribution is reusable theorem infrastructure connecting the AFP local-flow construction to global forward existence, uniqueness, forward invariance of the nonnegative orthant, conservation, monotonicity, the Kermack-McKendrick conserved phase-plane relation, compartment bounds, and threshold-ratio conditions for infectious growth and monotonicity. The proof first establishes sign and conservation facts for local AFP flow segments, then uses the conserved nonnegative simplex as the compactness witness for extending the flow to all forward times. The finite-interval qualitative facts are then transferred to the unique AFP forward flow on arbitrary intervals [0,b] with b>0, so the results apply to the constructed Isabelle/AFP SIR solution rather than to an assumed trajectory. The reusable layer provides homogeneous-linear scalar compartment lemmas for equations X'(t)=f(t)X(t), derivative-sign monotonicity, three-compartment conservation, and an SIR transfer bridge to the AFP flow infrastructure. We do not formalize stability, final-size, or asymptotic theory. The accompanying Isabelle artifact builds with Isabelle 2024 and AFP 2024 and contains no sorry or oops proof placeholders. △ Less

Submitted 4 May, 2026; originally announced May 2026.

Scalar-Electromagnetic Couplings as Source of Deformed Black Hole: From Shadows to Thermodynamic Topology

Authors: Ednaldo L. B. Junior, José Tarciso S. S. Junior, Francisco S. N. Lobo, Jorde A. A. Ramos, Manuel E. Rodrigues, Diego Rubiera-Garcia, Luís F. Dias da Silva, Henrique A. Vieira

Abstract: We reconstruct a static and spherically symmetric black hole geometry originally proposed as an effective metric by identifying a consistent matter source derived from a fundamental action. The space-time is supported by a magnetically charged nonlinear electrodynamics (NED) field non-minimally coupled to a scalar field. Dimensional consistency reduces the parameter space to a single magnetic char… ▽ More We reconstruct a static and spherically symmetric black hole geometry originally proposed as an effective metric by identifying a consistent matter source derived from a fundamental action. The space-time is supported by a magnetically charged nonlinear electrodynamics (NED) field non-minimally coupled to a scalar field. Dimensional consistency reduces the parameter space to a single magnetic charge, and the inverse construction formalism yields a one-parameter family of electromagnetic Lagrangians $\mathcal{L}(F)=F^{n+1}/(n+1)$, encompassing both linear and nonlinear electrodynamics. We analyze the horizon structure and determine the critical magnetic charge separating black hole and horizonless configurations. The photon sphere and the corresponding shadow radius are computed, and observational bounds from the Event Horizon Telescope for Sagittarius A* constrain the allowed range of the magnetic charge. In the extended phase space thermodynamics, the solution satisfies the first law and the Smarr relation, exhibits a Hawking-Page phase transition, and presents a single change in stability without van der Waals-type critical behavior. We also investigate the topological properties of both the photon sphere and the thermodynamic parameter space. The photon sphere carries a total topological charge $Q_{\text{tot}}=-1$, while the thermodynamic vector field yields a global winding number $W=0$, placing the solution in the same topological class as the one of the Reissner-Nordström black hole. We finally discuss the versatility of this non-minimal coupling framework in both providing theoretical support to previously introduced solution and also to connect them to observational settings within strong-field gravity. △ Less

Submitted 3 May, 2026; originally announced May 2026.

Comments: 15 pages, 10 figures

Stokes' Theorem for Smooth Singular Cubes in Lean 4: True Pullback, Bridges to mathlib4, and Chain-Level d^2=0

Authors: David B. Hulak, Arthur F. Ramos, Ruy J. G. B. de Queiroz

Abstract: We present a sorry-free Lean 4/mathlib4 formalization of Stokes' theorem for smooth singular cubes in arbitrary dimension, using true differential-form pullback via the Frechet derivative. The development also includes a bridge to mathlib4's abstract extDeriv, chain-level Stokes extended by Z-linearity, d^2=0 for singular cubical chains, box Stokes for axis-aligned cubes, dimensional specializatio… ▽ More We present a sorry-free Lean 4/mathlib4 formalization of Stokes' theorem for smooth singular cubes in arbitrary dimension, using true differential-form pullback via the Frechet derivative. The development also includes a bridge to mathlib4's abstract extDeriv, chain-level Stokes extended by Z-linearity, d^2=0 for singular cubical chains, box Stokes for axis-aligned cubes, dimensional specializations, and a structured comparison with Harrison's HOL Light formalization. △ Less

Submitted 1 May, 2026; originally announced May 2026.

Exterior-Model Spinors in Split Rank: Exact Levi Images and Square-Determinant Obstructions

Authors: Arthur F. Ramos, David B. Hulak, Ruy J. G. B. de Queiroz

Abstract: Let $K$ be a field with $2 \in K^\times$, and let $H_W$ denote the standard hyperbolic form on $W \oplus W^*$. We study the exterior spinor model $S = \bigwedge V(W)$ together with the spin-to-orthogonal map for this split form, keeping the chosen hyperbolic presentation explicit. The main results determine the field-sensitive part of the split Levi image. In positive split rank the kernel of… ▽ More Let $K$ be a field with $2 \in K^\times$, and let $H_W$ denote the standard hyperbolic form on $W \oplus W^*$. We study the exterior spinor model $S = \bigwedge V(W)$ together with the spin-to-orthogonal map for this split form, keeping the chosen hyperbolic presentation explicit. The main results determine the field-sensitive part of the split Levi image. In positive split rank the kernel of $\mathrm{Spin}(V,Q) \to SO(V,Q)$ is $\{\pm 1\}$; therefore the exterior spinor action descends to the orthogonal image only projectively. For the split line the image of $\mathrm{Spin}(H_K) \to SO(H_K)$ is precisely the square-scaling subgroup. In arbitrary split rank we construct explicit Clifford representatives for hyperbolic transvections and chosen-line square scalings, prove the weight-2 torus conjugation law, and show that any split Levi lift acts on $\bigwedge V(W)$ as a scalar multiple of the natural exterior action. If $\det(g) \in u^2$, the transported Levi element $\hat{g} = (g, g^{-\top})$ admits an explicit even unitary Clifford lift acting as $u^{-1} \bigwedge(g)$ on $S$. In finite split rank at least three, if $H_W \in \mathrm{im}(\mathrm{Spin}(H_W) \to SO(H_W))$, then $g_{H_W} \in \det(g) \cdot K^{\times 2}$. Equivalently, the spin image meets the split Levi subgroup exactly in its square-determinant subgroup. This recovers, by direct Clifford calculation, the determinant-modulo-squares spinor-norm criterion on the split Levi. △ Less

Submitted 28 April, 2026; originally announced April 2026.

Comments: 22 pages. Lean 4 companion formalization available at https://github.com/Arthur742Ramos/SpinorLean

MSC Class: 15A66; 11E81; 20G15

Pair-Trace Absorption Certificates for Regular Induced Subgraphs

Authors: Arthur F. Ramos, David Barros Hulak, Ruy J. G. B. de Queiroz

Abstract: We study a fixed-core absorption problem for regular induced subgraphs. A set is q-modular if all induced degrees are congruent modulo q. Given a q-modular witness A and a retained core U subset A, we ask when deleting equal-trace q-tuples from A\U can make U into a 2q-modular witness. The main contribution is a finite absorption-or-obstruction certificate. We give an exact quotient formula for th… ▽ More We study a fixed-core absorption problem for regular induced subgraphs. A set is q-modular if all induced degrees are congruent modulo q. Given a q-modular witness A and a retained core U subset A, we ask when deleting equal-trace q-tuples from A\U can make U into a 2q-modular witness. The main contribution is a finite absorption-or-obstruction certificate. We give an exact quotient formula for the deletion-tail obstruction in complement-orbit coordinates: the correct expression uses oriented differences n_B - n_{U\B}, not sums. Equal-trace q-tuples absorb exactly the span of their trace classes in F_2^U / 1_U. In particular, a connected graph of q-heavy two-point traces on U, together with one odd trace when |U| is even, absorbs every top-bit defect by deleting at most q(|U|-1) tail vertices. If fixed-core absorption fails, the obstruction is an explicit even parity cut of U. We also record the parity base, the terminal modular criterion, and a conditional modular-witness threshold theorem explaining the relevance to the Erdos-Fajtlowicz-Staton problem. The paper does not claim to solve that problem or to improve the general lower bound for F(n). △ Less

Submitted 26 April, 2026; originally announced April 2026.

Comments: 26 pages. Submitted to Discussiones Mathematicae Graph Theory

MSC Class: 05C35; 05C55; 05C50

Regular Black Holes in General Relativity from Nonlinear Electrodynamics with de Sitter Cores

Authors: A. A. Araújo Filho, Ednaldo L. B. Junior, José Tarciso S. S. Junior, Francisco S. N. Lobo, Jorde A. A. Ramos, Manuel E. Rodrigues, Diego Rubiera-Garcia, Luís F. Dias da Silva, Henrique A. Vieira

Abstract: We present new regular black hole solutions in general relativity (GR) within a static, spherically symmetric framework governed by a variable equation of state, following the approach of [Class. Quant. Grav. 42, 025024 (2025)]. The matter supporting these geometries is identified as a purely magnetic monopole configuration of the Maxwell-Faraday tensor in the context of nonlinear electrodynamics… ▽ More We present new regular black hole solutions in general relativity (GR) within a static, spherically symmetric framework governed by a variable equation of state, following the approach of [Class. Quant. Grav. 42, 025024 (2025)]. The matter supporting these geometries is identified as a purely magnetic monopole configuration of the Maxwell-Faraday tensor in the context of nonlinear electrodynamics (NLED). We explicitly reconstruct the corresponding NLED Lagrangian and analyze the asymptotic and central behaviors of the solutions. The geometric structure is examined through the metric functions, the regularity of the Kretschmann scalar, and the profiles of energy density and pressures, including a discussion of the resulting energy conditions. Using Event Horizon Telescope observations of Sgr A$^*$, we constrain the model parameters by comparing the predicted size of the central dark region with the inferred observational images, taking into account the effective geometry experienced by photons in the presence of NLED. Finally, we investigate the dynamical stability of these configurations under scalar perturbations by computing the quasinormal mode spectrum and performing a time-domain analysis. △ Less

Submitted 6 July, 2026; v1 submitted 21 April, 2026; originally announced April 2026.

Comments: 29 pages in double column, 23 figures and 10 tables -- version accepted for publication in Physics of the Dark Universe

Journal ref: Physics of the Dark Universe 53 (2026) 102396

Recursive Completion in Higher K-Models: Front-Seed Semantics, Proof-Relevant Witnesses, and the K-Infinity Model

Authors: Daniel O. Martinez-Rivillas, Arthur F. Ramos, Ruy J. G. B. de Queiroz

Abstract: Martinez-Rivillas and de Queiroz gave extensional Kan semantics for the untyped lambda-calculus and later constructed the concrete K-infinity homotopy-model. The two main mathematical results of the present paper are these. First, we show that a smaller front-seed coherence package (WL, WR) together with an inner-right-front pentagon contraction already suffices to recover the associator compariso… ▽ More Martinez-Rivillas and de Queiroz gave extensional Kan semantics for the untyped lambda-calculus and later constructed the concrete K-infinity homotopy-model. The two main mathematical results of the present paper are these. First, we show that a smaller front-seed coherence package (WL, WR) together with an inner-right-front pentagon contraction already suffices to recover the associator comparison, semantic pentagon, and bridge theorems used in the later semantic arguments. Second, we prove explicit global reify, reflect, and application formulas for K-infinity, with exact coordinatewise identities at every finite stage. We also record two structural clarifications: the recursive all-dimensional continuation of the explicit low-dimensional tower is obtained by a finite packaging phase followed by a uniform equality-generated recursion; and, on a deliberately fixed forward witness language for the classical separation span, the canonical identity-type higher tower on K-infinity forces all higher non-connection once the two witness classes land at distinct points. The paper is fully formalized in Lean 4, and the project sources contain no local uses of sorry, admit, or axiom. △ Less

Submitted 14 April, 2026; originally announced April 2026.

Comments: 26 pages; To be submitted to Journal of Logic and Computation, 2026; fully formalized in Lean 4 at https://github.com/Arthur742Ramos/HigherLambdaModel

MSC Class: 03B40; 68Q55; 18N50 ACM Class: F.3.2; F.4.1

On Optimality Conditions for Mathematical Programming Problems Based on Strong Subdifferentials

Authors: Felipe Lara, Alberto Ramos

Abstract: We develop refined Karush-Kuhn-Tucker (KKT) and Fritz-John (FJ)-type optimality conditions for nonsmooth, nonconvex mathematical pro\-gra\-mming problems. We pay special attention in the case that the functional constraint belongs to a specific class of generalized convex functions known as strongly quasiconvex functions. After analyzing a specialized sub\-di\-ffe\-ren\-tial, named the strong subd… ▽ More We develop refined Karush-Kuhn-Tucker (KKT) and Fritz-John (FJ)-type optimality conditions for nonsmooth, nonconvex mathematical pro\-gra\-mming problems. We pay special attention in the case that the functional constraint belongs to a specific class of generalized convex functions known as strongly quasiconvex functions. After analyzing a specialized sub\-di\-ffe\-ren\-tial, named the strong subdifferential, we compute the normal cone of the supremum function in terms of such subdifferentials, and apply this result to the mathematical programming problem. We illustrate our important results by examples. △ Less

Submitted 13 April, 2026; originally announced April 2026.

MSC Class: 90C26; 90C32

Token-Sensitive Enclosure Semantics for Measurement-Bearing Expressions

Authors: David B. Hulak, Arthur F. Ramos, Ruy J. G. B. de Queiroz

Abstract: Token identity is semantic information for measurement-bearing expressions. Intervals, dimension tags, and token-erased syntax can say what values a measured leaf may take, but they cannot say whether two occurrences name the same observation or two fresh observations. We give a small formal semantics in which each measured leaf carries an interval of possible exact values and an opaque observatio… ▽ More Token identity is semantic information for measurement-bearing expressions. Intervals, dimension tags, and token-erased syntax can say what values a measured leaf may take, but they cannot say whether two occurrences name the same observation or two fresh observations. We give a small formal semantics in which each measured leaf carries an interval of possible exact values and an opaque observation-event token. Here "token" means an identity for a measurement event, not a lexical token of the source syntax. The denotation of an expression is its warranted enclosure: the set of exact values still justified by hidden-value environments that assign one value to each observation token and respect the declared intervals. Over this semantics, e -> e' is a claim-tightening judgment, equivalently enclosure containment Encl(e') subseteq Encl(e), while interchangeability is equality of enclosures. The distinction is visible in cancellation, background subtraction, and self-division: reusing one token gives interchangeability with the expected simplified expression, while using distinct tokens gives only one-way containment. We prove that provenance-blind summaries of the kind studied here, preserving intervals, dimension tags, and token-erased syntax, are insufficient to recover the correct rewrite class. The formal results are mechanized in Lean 4 with no sorry or admit placeholders. △ Less

Submitted 29 April, 2026; v1 submitted 8 April, 2026; originally announced April 2026.

Comments: 17 pages; Lean 4 formalization; prepared for submission to South American Journal of Logic

A Prime-Generated Formalization of Nagata's Factoriality Theorem in Lean 4

Authors: Arthur F. Ramos, Ruy J. G. B. de Queiroz, Anjolina G. de Oliveira

Abstract: We present a Lean 4 Mathlib formalization of Nagata's factoriality theorem: if R is a noetherian domain and S <= R is a prime-generated submonoid such that S^{-1}R is a UFD, then R itself is a UFD. The prime-generated hypothesis -- every element of S is a finite product of primes belonging to S -- replaces a superficially cleaner but degenerate prime-or-unit condition that the formalization effort… ▽ More We present a Lean 4 Mathlib formalization of Nagata's factoriality theorem: if R is a noetherian domain and S <= R is a prime-generated submonoid such that S^{-1}R is a UFD, then R itself is a UFD. The prime-generated hypothesis -- every element of S is a finite product of primes belonging to S -- replaces a superficially cleaner but degenerate prime-or-unit condition that the formalization effort exposed. The development packages the theorem both for the concrete type Localization S and through abstract IsLocalization formulations. As applications, we formalize two Nagata-based proofs that R[X] is a UFD whenever R is a noetherian UFD: one via Laurent-polynomial localization at powers of X, and one via localization at the constant primes and identification with Frac(R)[X]. Reusing the same package, we also obtain the iterated polynomial corollary R[X][Y]. No public formalization of this result is known to us in Lean, Coq, or Isabelle. △ Less

Submitted 6 April, 2026; originally announced April 2026.

Comments: 23 pages. Formalization artifact available at https://github.com/Arthur742Ramos/NagataFactoriality (tagged afm-submission-draft-2026-04-04). Lean 4.24.0, Mathlib. No sorry/admit/axiom placeholders. 97 theorem/lemma declarations, 1352 lines of Lean source across 18 files

MSC Class: 03B35; 13A05; 13B30

Determination of $α_S$ in the $SU(3)$ Yang-Mills theory

Authors: Isabella Leone Zimmel, Alberto Ramos

Abstract: The decoupling strategy allows one to obtain the value of the strong coupling in QCD from the running in pure gauge. Here we present our strategy to determine the running in the $SU(3)$ Yang-Mills theory. We use a finite-volume scheme with twisted boundary conditions and a step-scaling approach based on a gradient-flow coupling. We show preliminary results for the continuum extrapolation of the st… ▽ More The decoupling strategy allows one to obtain the value of the strong coupling in QCD from the running in pure gauge. Here we present our strategy to determine the running in the $SU(3)$ Yang-Mills theory. We use a finite-volume scheme with twisted boundary conditions and a step-scaling approach based on a gradient-flow coupling. We show preliminary results for the continuum extrapolation of the step-scaling function. Compared with other finite-volume approaches, we expect a reduced statistical error and absence of linear cutoff effects due to the translational invariance of the boundary conditions. △ Less

Submitted 31 March, 2026; originally announced March 2026.

Comments: 10 pages, 4 figures. Proceedings of the 42nd International Symposium on Lattice Field Theory (Lattice 2025), TIFR Mumbai, India, 2025

Magnetoacoustic Shocks and Spectropolarimetric Signals in He I 10830 Å

Authors: Hirdesh Kumar, Tobias Felipe, Christoph Kuckein, S. J. González Manrique, A. Asensio Ramos

Abstract: Umbral flashes are manifestations of magnetoacoustic shocks in the solar chromosphere. These phenomena are thought to influence the evolution of chromospheric umbral magnetic fields. However, the impact of these shocks on inferred chromospheric magnetic field oscillations remains unclear. We examined five different sunspots located near the solar disk center, observed with the GRIS instrument inst… ▽ More Umbral flashes are manifestations of magnetoacoustic shocks in the solar chromosphere. These phenomena are thought to influence the evolution of chromospheric umbral magnetic fields. However, the impact of these shocks on inferred chromospheric magnetic field oscillations remains unclear. We examined five different sunspots located near the solar disk center, observed with the GRIS instrument installed at the GREGOR telescope. The HAZEL2 Spectropolarimetric inversion code is used to obtain the photospheric and chromospheric line-of-sight velocities and magnetic fields in Si 10827 Å and He 10830 Å spectral lines, respectively, using various inversion strategies. In the inversions with one chromospheric component, three of the sunspots exhibit remarkably stronger magnetic fields accompanying the shocks, while the other two sunspots show striking reductions in the magnetic field. Alternatively, the Stokes profiles can be reproduced by models with two chromospheric slabs, one on top of the other, through two-component inversions. These inversions provide excellent fits even when magnetic field fluctuations are discarded by imposing a constant magnetic field during the whole temporal series. In this scenario, the observed Stokes profiles are interpreted as the result of strong velocity gradients, where the He 10830 Å line is sensitive to both sides of the shock front. Both competing models explaining the spectral profiles during the shocks, either large magnetic field fluctuations or velocity gradients, are critically discussed. △ Less

Submitted 12 March, 2026; originally announced March 2026.

Comments: 13 Pages, 3 Tables, 7 Figures, Accepted for publication in the Astrophysical Journal

Linear codes arising from geometrical operation

Authors: Antonio Jesús Lorite López, Daniel Camazón Portela, Juan Antonio López Ramos

Abstract: We construct linear codes over the finite field Fq from arbitrary simplicial complexes, establishing a connection between topological properties and fundamental coding parameters. First, we study the behaviour of the weights of codewords from a geometric point of view, interpreting them in terms of the combinatorial structure of the associated simplicial complex. This approach allows us to describ… ▽ More We construct linear codes over the finite field Fq from arbitrary simplicial complexes, establishing a connection between topological properties and fundamental coding parameters. First, we study the behaviour of the weights of codewords from a geometric point of view, interpreting them in terms of the combinatorial structure of the associated simplicial complex. This approach allows us to describe the minimum distance of the codes in terms of certain geometric features of the complex. Subsequently, we analyse how various topological operations on simplicial complexes affect the classical parameters of the codes. This study leads to the formulation of geometric criteria that make it possible to explicitly control and manipulate these parameters. Finally, as an application of the obtained results, we construct several families of optimal linear codes over F2 using these geometric methods. Thanks to the previously established geometric properties, we can precisely determine the parameters of these families. △ Less

Submitted 4 March, 2026; originally announced March 2026.

MSC Class: 94B05; 94B27

Effect of glass stability on the low frequency vibrations of vapor deposited glasses

Authors: I. Festi, E. Alfinelli, D. Bessas, F. Caporaletti, A. I. Chumakov, M. Moratalla, M. A. Ramos, M. Rodríguez-López, C. Rodríguez-Tinoco, J. Rodríguez-Viejo, G. Baldi

Abstract: Ultra-stable glasses prepared from the physical vapor deposition of organic molecules present a very low density of two-level states, the kind of glass defects that determine their peculiar low temperature thermal properties. Numerical simulations suggest that quasi-localized harmonic vibrational modes emerge in the soft regions associated with two-level states. However, the connection between the… ▽ More Ultra-stable glasses prepared from the physical vapor deposition of organic molecules present a very low density of two-level states, the kind of glass defects that determine their peculiar low temperature thermal properties. Numerical simulations suggest that quasi-localized harmonic vibrational modes emerge in the soft regions associated with two-level states. However, the connection between the low frequency vibrational modes and the local structural instabilities of glasses remains unexplained. Here we exploit a recently developed spectrograph for nuclear resonant analysis of inelastic X-ray scattering to probe the density of vibrational states of amorphous thin films of ultra-stable and conventional glasses down to an exceptionally low frequency of $\sim 70$ GHz. We show that the glass stability does not affect the harmonic vibrational modes at the lowest frequencies, despite a reduction of almost an order of magnitude in the density of two-level states. At the same time, the vibrational modes at higher frequencies, around the boson peak maximum, are extremely sensitive to the glass stability. Although we cannot exclude the possible existence of quasi-localized modes in glasses, we show that their presence is not strictly necessary to describe the measured density of low frequency vibrations. The experimental developments here presented pave the way to the solution to the long-standing debate on the low frequency vibrations in glasses. △ Less

Submitted 25 February, 2026; originally announced February 2026.

Comments: 19 pages, 13 figures. Phys. Rev. X - Accepted 23 February, 2026. DOI: https://doi.org/10.1103/311v-1ftn

Infrared spectropolarimetry of a C-class solar flare footpoint plasma -- I. Spectral features and forward modelling

Authors: Z. Vashalomidze, C. Quintero Noda, T. V. Zaqarashvili, M. Benko, D. Kuridze, P. Gömöry, J. Rybák, S. Lomineishvili, M. Collados, C. Denker, M. Verma, C. Kuckein, A. Asensio Ramos

Abstract: We performed high-spatial resolution spectropolarimetric observations of active region NOAA 13363 during a C-class flare with the Gregor Infrared Spectrograph (GRIS) on 16 July 2023. We examine the coupling between the photosphere and the chromosphere, studying the polarimetric signals during a period that encompasses the decaying phase of a C-class flare and the appearance of a new C-class flare… ▽ More We performed high-spatial resolution spectropolarimetric observations of active region NOAA 13363 during a C-class flare with the Gregor Infrared Spectrograph (GRIS) on 16 July 2023. We examine the coupling between the photosphere and the chromosphere, studying the polarimetric signals during a period that encompasses the decaying phase of a C-class flare and the appearance of a new C-class flare at the same location. We focus on the analysis of various spectral lines. In particular, we study the Si I 10827 Å, Ca I 10833.4 Å, Na I 10834.9 Å, and Ca I 10838.9 Å photospheric lines, as well as the He I 10830 Å triplet. GRIS data revealed the presence of flare-related red- and blueshifted spectral line components, reaching Doppler velocities up to 90 km/s, and complex Si I profiles where the He i spectral line contribution is blueshifted. In contrast, the photospheric Ca i and Na i transitions remained unchanged, indicating that the flare did not modify the physical conditions of the lower photosphere. We combined that information with simultaneous imaging in the Ca ii H line and TiO band with the improved High-resolution Fast Imager (HiFI+), finding that the flare emission did not affect the inverse granulation or nearby plage, in agreement with the results from GRIS. We also complement the previous studies with a forward modelling computation, concluding that the He I spectral line emission reflects a complex response of the flaring chromosphere. Radiative excitation from coronal EUV irradiation, energy deposition by flare-accelerated electrons, and dynamic field-aligned plasma flows likely act together to produce the observed supersonic downflows and upflows. We plan to expand these findings through inversions of the He I 10830 Å triplet signals in the future. △ Less

Submitted 24 February, 2026; originally announced February 2026.

Comments: Published in A&A, 10 pages, 8 figures,

Journal ref: A&A, 706,A116 (2026)

Inference of horizontal velocity fields from the induction equation in the solar atmosphere. I. Analytical and numerical solutions in 2D

Authors: H. Vila Crespo, J. M. Borrero, I. Milić, G. Vigeesh, A. Asensio Ramos

Abstract: Spectroscopic and spectropolarimetric observations, which rely on the Doppler effect, only provide access to the line-of-sight component of the solar plasma velocity (vz). However, many dynamic processes in the solar atmosphere involve strong horizontal motions (in the plane perpendicular to the line-of-sight: vx, vy). Existing methods for estimating horizontal velocities are generally insensitive… ▽ More Spectroscopic and spectropolarimetric observations, which rely on the Doppler effect, only provide access to the line-of-sight component of the solar plasma velocity (vz). However, many dynamic processes in the solar atmosphere involve strong horizontal motions (in the plane perpendicular to the line-of-sight: vx, vy). Existing methods for estimating horizontal velocities are generally insensitive to variations in height (the z-coordinate), providing them only on a single plane perpendicular to the line-of-sight: vx(x,y), vy(x,y). Motivated by the fact that modern analysis techniques allow us to retrieve the height dependence of vz and B, our goal is to infer also this height dependence for the horizontal velocity field in the solar atmosphere. As a first step, we present, and test a method for the two-dimensional case on the (y,z) plane so as to show that the z dependence can be successfully retrieved. The components of the two-dimensional magnetic induction equation are discretized via finite differences, leading to an overdetermined system whose solution provides vy. The method assumes that B, its time variation, as well as vz are known. This is currently possible through modern Stokes inversion techniques applied to spatially and temporally resolved spectropolarimetric observations. Using analytically prescribed values and two-dimensional magneto-hydrodynamic simulations of the solar surface, we demonstrate that, in these idealized cases, the horizontal velocity component in a two-dimensional domain, can be successfully recovered with a mean error of about 1 %. The proposed method successfully retrieves the horizontal velocity field in the (y,z) plane, thereby establishing the foundation for future extensions to three-dimensional reconstructions of the horizontal velocity field. △ Less

Submitted 27 March, 2026; v1 submitted 17 February, 2026; originally announced February 2026.

Comments: 10 pages, 9 figures

Journal ref: A&A 707, A306 (2026)

NanoFLUX: Distillation-Driven Compression of Large Text-to-Image Generation Models for Mobile Devices

Authors: Ruchika Chavhan, Malcolm Chadwick, Alberto Gil Couto Pimentel Ramos, Luca Morreale, Mehdi Noroozi, Abhinav Mehrotra

Abstract: While large-scale text-to-image diffusion models continue to improve in visual quality, their increasing scale has widened the gap between state-of-the-art models and on-device solutions. To address this gap, we introduce NanoFLUX, a 2.4B text-to-image flow-matching model distilled from 17B FLUX.1-Schnell using a progressive compression pipeline designed to preserve generation quality. Our contrib… ▽ More While large-scale text-to-image diffusion models continue to improve in visual quality, their increasing scale has widened the gap between state-of-the-art models and on-device solutions. To address this gap, we introduce NanoFLUX, a 2.4B text-to-image flow-matching model distilled from 17B FLUX.1-Schnell using a progressive compression pipeline designed to preserve generation quality. Our contributions include: (1) A model compression strategy driven by pruning redundant components in the diffusion transformer, reducing its size from 12B to 2B; (2) A ResNet-based token downsampling mechanism that reduces latency by allowing intermediate blocks to operate on lower-resolution tokens while preserving high-resolution processing elsewhere; (3) A novel text encoder distillation approach that leverages visual signals from early layers of the denoiser during sampling. Empirically, NanoFLUX generates 512 x 512 images in approximately 2.5 seconds on mobile devices, demonstrating the feasibility of high-quality on-device text-to-image generation. △ Less

Submitted 6 February, 2026; originally announced February 2026.

RFDM: Residual Flow Diffusion Model for Efficient Causal Video Editing

Authors: Mohammadreza Salehi, Mehdi Noroozi, Luca Morreale, Ruchika Chavhan, Malcolm Chadwick, Alberto Gil Ramos, Abhinav Mehrotra

Abstract: Instructional video editing applies edits to an input video using only text prompts, enabling intuitive natural-language control. Despite rapid progress, most methods still require fixed-length inputs and substantial compute. Meanwhile, autoregressive video generation enables efficient variable-length synthesis, yet remains under-explored for video editing. We introduce a causal, efficient video e… ▽ More Instructional video editing applies edits to an input video using only text prompts, enabling intuitive natural-language control. Despite rapid progress, most methods still require fixed-length inputs and substantial compute. Meanwhile, autoregressive video generation enables efficient variable-length synthesis, yet remains under-explored for video editing. We introduce a causal, efficient video editing model that edits variable-length videos frame by frame. For efficiency, we start from a 2D image-to-image (I2I) diffusion model and adapt it to video-to-video (V2V) editing by conditioning the edit at time step t on the model's prediction at t-1. To leverage videos' temporal redundancy, we propose a new I2I diffusion forward process formulation that encourages the model to predict the residual between the target output and the previous prediction. We call this Residual Flow Diffusion Model (RFDM), which focuses the denoising process on changes between consecutive frames. Moreover, we propose a new benchmark that better ranks state-of-the-art methods for editing tasks. Trained on paired video data for global/local style transfer and object removal, RFDM surpasses I2I-based methods and competes with fully spatiotemporal (3D) V2V models, while matching the compute of image models and scaling independently of input video length. More content can be found in: https://smsd75.github.io/RFDM_page/ △ Less

Submitted 28 February, 2026; v1 submitted 6 February, 2026; originally announced February 2026.

Comments: Accepted at CVPR26

Dynamical Stability of Translating Solitons to Mean Curvature Flow in Hyperbolic Space

Authors: Ronaldo F. de Lima, Álvaro K. Ramos

Abstract: We develop the theory of translating solitons for the Mean Curvature Flow (MCF) in hyperbolic space of dimension $n+1\ge 3$. More specifically, we establish that horospheres are dynamically stable as radial graphical solutions to MCF. To that end, we construct rotationally invariant translators analogous to the winglike solitons introduced by Clutterbuck, Schnürer and Schulze, which serve as barri… ▽ More We develop the theory of translating solitons for the Mean Curvature Flow (MCF) in hyperbolic space of dimension $n+1\ge 3$. More specifically, we establish that horospheres are dynamically stable as radial graphical solutions to MCF. To that end, we construct rotationally invariant translators analogous to the winglike solitons introduced by Clutterbuck, Schnürer and Schulze, which serve as barriers in an argument based on White's avoidance principle and the strong maximum principle for parabolic PDEs. △ Less

Submitted 2 February, 2026; originally announced February 2026.

Comments: 13 pages, 3 figures. Comments are welcome

Chemical study of two starless cores in the B213/L1495 filament

Authors: L. Moral-Almansa, A. Fuente, M. Rodríguez-Baras, T. Alonso-Albi, G. Esplugues, D. Navarro-Almaida, P. Riviére-Marichalar, B. Tercero, A. Asensio Ramos, C. Westendorp Plaza

Abstract: The chemical evolution of pre-stellar cores during their transition to a protostellar stage is not yet fully understood. Detailed chemical characterizations of these sources are needed to better define their chemistry during star formation. Our goal is to characterize the chemistry of the starless cores C2 and C16 in the B213/L1495 filament of the Taurus Molecular Cloud, and to understand how it r… ▽ More The chemical evolution of pre-stellar cores during their transition to a protostellar stage is not yet fully understood. Detailed chemical characterizations of these sources are needed to better define their chemistry during star formation. Our goal is to characterize the chemistry of the starless cores C2 and C16 in the B213/L1495 filament of the Taurus Molecular Cloud, and to understand how it relates to the environmental conditions and the evolutionary state of the cores. We made use of two complete spectral surveys at 7 mm of these sources, carried out using the Yebes 40-m telescope. Derived molecular abundances were compared with those of other sources in different evolutionary stages and with values computed by chemical models. Including isotopologs, 22 molecules were detected in B213-C2, and 25 in B213-C16. The derived rotational temperatures have values of between $\sim$ 5 K and $\sim$ 9 K. A comparison of the two sources shows lower abundances in C2, except for l-C$_{3}$H and HOCO$^{+}$, which have similar values in both cores. Model results indicate that both cores are best fit assuming early-time chemistry, and point to C2 being in a more advanced evolutionary stage, as it presents a higher molecular hydrogen density and sulfur depletion, and a lower cosmic-ray ionization rate. Our chemical modeling successfully accounts for the abundances of most molecules, including complex organic molecules and long cyanopolynes (HC$_{5}$N, HC$_{7}$N), but fails to reproduce those of the carbon chains CCS and C$_{3}$O. Chemical differences between C2 and C16 could stem from the evolutionary stage of the cores, with C2 being closer to the pre-stellar phase. Both cores are better fit assuming early-time chemistry of t $\sim$ 0.1 Myr. The more intense UV radiation in the northern region of B213 could account for the high abundances of l-C$_{3}$H and HOCO$^{+}$ in C2. △ Less

Submitted 26 January, 2026; originally announced January 2026.

Generalized sums of linear orders

Authors: Álvaro Díaz Ramos, Garrett Ervin, Saharon Shelah

Abstract: We study generalized sums of linear orders. These are binary operations that, given linear orders $A$ and $B$, return an order $A \oplus B$ that can be decomposed as an isomorphic copy of $A$ interleaved with a copy of $B$. We show that there is a rich array of associative sums different from the usual sum $+$ and its dual. The simplest of these sums arise from what we call sum-generating classes… ▽ More We study generalized sums of linear orders. These are binary operations that, given linear orders $A$ and $B$, return an order $A \oplus B$ that can be decomposed as an isomorphic copy of $A$ interleaved with a copy of $B$. We show that there is a rich array of associative sums different from the usual sum $+$ and its dual. The simplest of these sums arise from what we call sum-generating classes of linear orders. These classes determine canonical decompositions of every linear order into left and right halves. We study the structural and algebraic properties of these classes along with the sums they generate. We then turn our attention to commutative sums on various subclasses of the linear orders. For this, we introduce the notion of a complicated class of linear orders and show that over such classes sums can be constructed in a very flexible way. Using this construction, we prove the existence of associative sums lacking the structural properties of the usual sum. Along the way, we characterize the associative and commutative sums on the ordinals. △ Less

Submitted 15 December, 2025; originally announced December 2025.

MSC Class: 06A05 (Primary) 03E10 (Secondary)

High-resolution broadband characterization of resonance dispersion in an optical microresonator

Authors: Romain Dalidet, Adrien Bensemhoun, Gregory Sauder, Anthony Martin, David Medina, Carlos Alonso Ramos, Eric Cassan, Laurent Vivien, Jonathan Faugier Tovar, Baptiste Routier, Quentin Wilmart, Ségolène Olivier, Virginia D Auria, Laurent Labonté, Sébastien Tanzilli

Abstract: Accurate knowledge of the uneven free spectral range of an optical microresonator, which provides direct insight into group velocity dispersion, is essential for understanding and controlling Kerr frequency comb dynamics. In this work, we present a simple and highly precise method formeasuring the free spectral range over a 5 THz bandwidth in silicon nitride microresonators, leveraging a wavemeter… ▽ More Accurate knowledge of the uneven free spectral range of an optical microresonator, which provides direct insight into group velocity dispersion, is essential for understanding and controlling Kerr frequency comb dynamics. In this work, we present a simple and highly precise method formeasuring the free spectral range over a 5 THz bandwidth in silicon nitride microresonators, leveraging a wavemeter with 0.4 MHz resolution. Our fully fibered plug-and-play experimental setup enables the accurate extraction of resonance frequencies. By carefully analyzing the spectral position of each resonance, we measure both second- and third-order free spectral range expansion coefficients. This approach offers a robust and accessible tool for dispersion characterization in integrated photonic circuits, paving the way for next-generation of Kerr comb sources and quantum photonic technologies. △ Less

Submitted 10 December, 2025; originally announced December 2025.

A Modular Lean 4 Framework for Confluence and Strong Normalization of Lambda Calculi with Products and Sums

Authors: Arthur Ramos, Anjolina Oliveira, Ruy de Queiroz, Tiago de Veras

Abstract: We present Metatheory, a comprehensive library for programming language foundations in Lean 4. The library features a modular framework for proving confluence of abstract rewriting systems using three classical proof techniques: the diamond property, Newmans lemma, and the Hindley-Rosen lemma. These are instantiated across six case studies including untyped lambda calculus, combinatory logic, term… ▽ More We present Metatheory, a comprehensive library for programming language foundations in Lean 4. The library features a modular framework for proving confluence of abstract rewriting systems using three classical proof techniques: the diamond property, Newmans lemma, and the Hindley-Rosen lemma. These are instantiated across six case studies including untyped lambda calculus, combinatory logic, term rewriting, simply typed lambda calculus, and STLC with products and sums. All theorems are fully mechanized with zero axioms or sorry statements. We provide complete proofs of de Bruijn substitution infrastructure and demonstrate strong normalization via logical relations. To our knowledge, this is the first comprehensive confluence and normalization framework for Lean 4. △ Less

Submitted 9 December, 2025; originally announced December 2025.

Comments: 15 pages, 2 figures, 1 table. Complete Lean 4 formalization with 10,367 lines of code and 497 fully mechanized theorems

MSC Class: 03B70; 03B15; 68Q42 ACM Class: F.3.1; F.3.2; F.4.1

CTAO LST-1 observations of magnetar SGR 1935+2154: Deep limits on sub-second bursts and persistent tera-electronvolt emission

Authors: K. Abe, S. Abe, A. Abhishek, F. Acero, A. Aguasca-Cabot, I. Agudo, C. Alispach, D. Ambrosino, F. Ambrosino, L. A. Antonelli, C. Aramo, A. Arbet-Engels, C. Arcaro, T. T. H. Arnesen, K. Asano, P. Aubert, A. Baktash, M. Balbo, A. Bamba, A. Baquero Larriva, U. Barres de Almeida, J. A. Barrio, L. Barrios Jiménez, I. Batkovic, J. Baxter , et al. (311 additional authors not shown)

Abstract: The Galactic magnetar SGR 1935+2154 has exhibited prolific high-energy (HE) bursting activity in recent years. Investigating its potential tera-electronvolt counterpart could provide insights into the underlying mechanisms of magnetar emission and very high-energy (VHE) processes in extreme astrophysical environments. We aim to search for a possible tera-electronvolt counterpart to both its persis… ▽ More The Galactic magnetar SGR 1935+2154 has exhibited prolific high-energy (HE) bursting activity in recent years. Investigating its potential tera-electronvolt counterpart could provide insights into the underlying mechanisms of magnetar emission and very high-energy (VHE) processes in extreme astrophysical environments. We aim to search for a possible tera-electronvolt counterpart to both its persistent and sub-second-scale burst emission. We analysed over 25 h of observations from the Large-Sized Telescope prototype (LST-1) of the Cherenkov Telescope Array Observatory (CTAO) during periods of HE activity from SGR 1935+2154 in 2021 and 2022 to search for persistent emission. For bursting emission, we selected and analysed nine 0.1 s time windows centred around known short X-ray bursts, targeting potential sub-second-scale tera-electronvolt counterparts in a low-photon-statistics regime. While no persistent or bursting emission was detected in our search, we establish upper limits for the tera-electronvolt emission of a short magnetar burst simultaneous to its soft gamma-ray flux. Specifically, for the brightest burst in our sample, the ratio between tera-electronvolt and X-ray flux is less than $10^{-3}$. The non-detection of either persistent or bursting tera-electronvolt emission from SGR 1935+2154 suggests that if such components exist, they may occur under specific conditions not covered by our observations. This aligns with theoretical predictions of VHE components in magnetar-powered fast radio bursts and the detection of MeV - GeV emission in giant magnetar flares. These findings underscore the potential of magnetars, fast radio bursts, and other fast transients as promising candidates for future observations in the low-photon-statistics regime with Imaging Atmospheric Cherenkov Telescopes, particularly with the CTAO. △ Less

Submitted 5 December, 2025; originally announced December 2025.

Comments: 13 pages, 5 figures. Accepted for publication in Astronomy & Astrophysics

Acceleration of Parallel Tempering for Markov Chain Monte Carlo methods

Authors: Aingeru Ramos, Jose A Pascual, Javier Navaridas, Ivan Coluzza

Abstract: Markov Chain Monte Carlo methods are algorithms used to sample probability distributions, commonly used to sample the Boltzmann distribution of physical/chemical models (e.g., protein folding, Ising model, etc.). This allows us to study their properties by sampling the most probable states of those systems. However, the sampling capabilities of these methods are not sufficiently accurate when hand… ▽ More Markov Chain Monte Carlo methods are algorithms used to sample probability distributions, commonly used to sample the Boltzmann distribution of physical/chemical models (e.g., protein folding, Ising model, etc.). This allows us to study their properties by sampling the most probable states of those systems. However, the sampling capabilities of these methods are not sufficiently accurate when handling complex configuration spaces. This has resulted in the development of new techniques that improve sampling accuracy, usually at the expense of increasing the computational cost. One of such techniques is Parallel Tempering which improves accuracy by running several replicas which periodically exchange their states. Computationally, this imposes a significant slow-down, which can be counteracted by means of parallelization. These schemes enable MCMC/PT techniques to be run more effectively and allow larger models to be studied. In this work, we present a parallel implementation of Metropolis-Hastings with Parallel Tempering, using OpenMP and CUDA for the parallelization in modern CPUs and GPUs, respectively. The results show a maximum speed-up of 52x using OpenMP with 48 cores, and of 986x speed-up with the CUDA version. Furthermore, the results serve as a basic benchmark to compare a future quantum implementation of the same algorithm. △ Less

Submitted 3 December, 2025; originally announced December 2025.

Comments: 14 pages, 7 figures (5 of them composed by 2 subfigures)

The Seifert-van Kampen Theorem via Computational Paths: A Formalized Approach to Computing Fundamental Groups

Authors: Arthur F. Ramos, Tiago M. L. de Veras, Ruy J. G. B. de Queiroz, Anjolina G. de Oliveira

Abstract: The Seifert-van Kampen theorem computes the fundamental group of a space from the fundamental groups of its constituents. We develop a modular SVK framework within the setting of computational paths - an approach to equality where witnesses are explicit sequences of rewrites governed by the LNDEQ-TRS. Our contributions are: (i) pushouts as higher-inductive types with modular typeclass assumptions… ▽ More The Seifert-van Kampen theorem computes the fundamental group of a space from the fundamental groups of its constituents. We develop a modular SVK framework within the setting of computational paths - an approach to equality where witnesses are explicit sequences of rewrites governed by the LNDEQ-TRS. Our contributions are: (i) pushouts as higher-inductive types with modular typeclass assumptions for computation rules; (ii) free products and amalgamated free products as quotients of word representations; (iii) an SVK equivalence schema parametric in user-supplied encode/decode structure; and (iv) instantiations for classical spaces - figure-eight (pi_1(S^1 v S^1) = Z * Z), 2-sphere (pi_1(S^2) = 1), and 3-sphere (pi_1(S^3) = 1) with Hopf fibration context. Recent extensions include higher homotopy groups pi_n via weak infinity-groupoid structure (with pi_2 abelian via Eckmann-Hilton), and pi_1 >= 1 in the 1-groupoid truncated setting; truncation levels connecting the framework to HoTT; automated path simplification tactics; basic covering space theory with pi_1-actions on fibers; fibration theory with long exact sequences; and Eilenberg-MacLane space characterization (S^1 = K(Z,1)). The development is formalized in Lean 4 with 41,130 lines across 107 modules, using 36 kernel axioms for HIT type-constructor declarations. △ Less

Submitted 23 December, 2025; v1 submitted 2 December, 2025; originally announced December 2025.

Comments: 29 pages, 6 figures, 107 modules. Lean 4 formalization available at https://github.com/Arthur742Ramos/ComputationalPathsLean

MSC Class: 55Q05; 03B38; 68N18 ACM Class: F.4.1; I.1.3

Silicate emission in a type-2 quasar: JWST/MIRI constraints on torus geometry and radiative feedback

Authors: C. Ramos Almeida, A. Asensio Ramos, C. Westerdorp Plaza, I. García-Bernete, E. Lopez-Rodriguez, S. Hönig, A. Audibert, S. García-Burillo, M. Pereira-Santaella, F. Donnan, A. Alonso-Herrero, O. González-Martín, N. Levenson, D. Rigopoulou, C. Tadhunter, G. Speranza

Abstract: Type-2 quasars (QSO2s) are AGN seen through a significant amount of dust and gas that obscures the central supermassive black hole and the broad line region. Despite this, recent mid-infrared spectra of the central 0.5-1.1 kpc of five QSO2s at z~0.1, obtained with the MRS module of JWST/MIRI, revealed 9.7, 18, and 23 micron silicate features in emission in two of them. This indicates that the high… ▽ More Type-2 quasars (QSO2s) are AGN seen through a significant amount of dust and gas that obscures the central supermassive black hole and the broad line region. Despite this, recent mid-infrared spectra of the central 0.5-1.1 kpc of five QSO2s at z~0.1, obtained with the MRS module of JWST/MIRI, revealed 9.7, 18, and 23 micron silicate features in emission in two of them. This indicates that the high angular resolution of JWST/MIRI now allows us to peer into their nuclear region, exposing some of the directly illuminated dusty clouds that produce silicate emission. To test this, we fitted the nuclear mid-infrared spectrum of the QSO2 with the strongest silicate features, J1010, with two different sets of torus models implemented in an updated version of the Bayesian tool {\tt BayesClumpy}. These are the CLUMPY and the CAT3D-WIND models. The CAT3D-WIND model is preferred by the observations based on the marginal likelihood and fit residuals, although the two torus models successfully reproduce the spectrum by means of intermediate covering factors ($\rm C_T=0.45\pm^{0.26}_{0.18}$ and $\rm C_T=0.66\pm^{0.16}_{0.17}$ for the CLUMPY and CAT3D-WIND models) and low inclinations ($\rm i=50^\circ\pm^{8^\circ}_{9^\circ}$ and $\rm i=13^\circ\pm^{7^\circ}_{6^\circ}$). Indeed, four of the five QSO2s with JWST/MIRI observations, including J1010, are in the blowout or ''forbidden'' region of the Eddington ratio-column density diagram, indicating that they are actively clearing gas and dust from their nuclear regions, leading to reduced covering factors. This is in contrast with Seyfert 2 galaxies observed with JWST, which are in the ''permitted'' regions of the diagram and show 9.7 micron silicate features in absorption. This supports a scenario where the more luminous the AGN and the higher their Eddington ratio, the lower the torus covering factor, driven by radiation pressure on dusty gas. △ Less

Submitted 2 December, 2025; originally announced December 2025.

Comments: 14 pages, 7 figures. Accepted for publication in A&A

Journal ref: A&A 706, A100 (2026)