arXiv subjects

Anil Kumar

Publications and source records attributed to Anil Kumar.

At least 19 recordsLinked to original sources

arXiv2026

Non-equilibrium modelling of polyatomic gases: generic framework and 11-moment model

In this study, we present a thermodynamically consistent framework for modelling polyatomic gases by integrating the \textit{general equation for non-equilibrium reversible-irreversible coupling} (GENERIC) with an 11-moment description. Our formulation unifies \textit{rational irreversible thermodynamics} (RIT) and \textit{extended irreversible thermodynamics} (EIT) into a single GENERIC-compatible structure that guarantees compliance with the second law of thermodynamics through the explicit construction of Poisson and friction matrices. By including translational and internal temperatures, as well as a temperature tensor, the model offers a well-structured and physically meaningful representation of non-equilibrium behavior in polyatomic gases. The entropy production is inherently non-negative, and all closure relations emerge naturally from thermodynamic principles. As a test of applicability, we compute the shock wave structure in nitrogen gas, validating the framework against Direct Simulation Monte Carlo (DSMC) simulations and experiments up to moderate Mach numbers.

math-ph↗

arXiv2026

Density-induced dark-baryon conversion in $\Delta-$admixed hypernuclear neutron stars

We investigate density-induced conversion of neutrons into a neutral dark baryon $\chi$ in cold, charge-neutral, $\beta$-equilibrated neutron-star matter containing hyperons and all $\Delta(1232)$ quartet. The hadronic sector is modeled within a density-dependent covariant density-functional framework using the DDME2 parametrization. A scalar Higgs portal is included as a possible interaction channel between the visible and dark sectors, although its mean-field contribution is negligible for the couplings adopted here. Unlike fixed dark-matter admixture models or scenarios in which nucleon-to-DM conversion is driven by Higgs exchange, the $\chi$ abundance is determined self-consistently from chemical equilibrium and baryon-number conservation. We find that hyperons and $\Delta$ resonances alter the neutron chemical potential, delay the onset of $\chi$, and suppress its abundance relative to nucleonic matter. This competition induces characteristic changes in the equation of state, particle fractions, sound speed, and adiabatic index. For $m_\chi=1250$, $1300$, and $1400$ MeV, the maximum masses of the complete $N+Y+\Delta+\chi$ configurations are $1.806$, $1.899$, and $2.024,M_\odot$, respectively, indicating that the massive-pulsar constraint disfavors the lighter dark-baryon benchmarks. The radial profiles further show that for $m_\chi=1400$ MeV, $\chi$ is confined to the inner core of the most massive stars, while canonical configurations remain essentially unaffected. Thus, the stellar modifications arise primarily from conversion-induced rearrangement of the equilibrium composition rather than from Higgs-mediated interactions. These results highlight the importance of treating conventional non-nucleonic degrees of freedom and density-generated dark baryons on an equal footing when assessing the astrophysical viability of dark-sector extensions of dense matter.

astro-ph.HE↗

arXiv2026

A windy sea surface with Stokes waves

Predicting the transition of wind-forced, gravito-capillary surface waves from smooth to corrugated states remains a longstanding problem in nonlinear surface wave mechanics. Solving driven-dissipative, nonlinear potential flow equations we map these waves ($4-13$ cm) onto a Reynolds number -- wave energy phase-space. We identify a transition band separating smooth from corrugated wave states - the wave steepness exhibits a non-monotonic dependence on Reynolds number within this. Subharmonic (in)stability analysis reveals that the fastest-growing mode intensifies corrugations on alternate faces of the carrier wave. Our results offer insights into parasitic capillary wave formation on steep carrier waves and are of interest to ocean remote-sensing.

physics.flu-dyn↗

arXiv2026

Real-time THz ptychography using an optically modulated aperture

Ptychography allows ordinary cameras to perform both quantitative phase and intensity imaging. However, the requirement for relative object to probe motion and high measurement count significantly limits imaging speed and application scope. In this work, we introduce optically modulated aperture ptychography, using a silicon photomodulator as a rapidly reconfigurable aperture, deployable across the microwave, millimeter wave and terahertz bands. We demonstrate experimentally at ~ 0.1 THz real-time ptychographic image capture, without moving parts. Furthermore, a reconfigurable aperture facilitates diverse and spatially multiplexed probes. We use a multiplexed known-probe reconstruction strategy that improves signal-to-noise ratio and increases the information content per measurement, enabling the capture of fluid dynamics at 16 fps. Our optical modulation approach enables high-throughput ptychographic imaging of dynamic samples, for applications such as non-destructive evaluation and in-vivo biomedical imaging.

physics.optics↗

arXiv2026

Strongly interacting matter with criticality induced by modified excluded volume in core-collapse supernova simulations

This article reviews critically the core-collapse supernova explosion mechanism associated with a sufficiently strong first-order phase transition from normal nuclear, in general hadronic matter to deconfined quark matter, which commonly assumes Gibbs conditions for the coexistence of phases and a phase transition construction accordingly. To this end, a novel class of multi-purpose equation of state (EOS) is developed, based on the modified excluded volume (MEV) approach employing a medium-dependent excluded-volume functional within the relativistic mean field framework with density-dependent meson-nucleon couplings. The chosen MEV parametrisation features the change in the number of degrees of freedom, mimicking the EOS softening in excess of nuclear saturation density, featuring a first-order phase transition with van der Waals like behaviour and the presence of a critical point at high temperatures. Simulations of core-collapse supernovae are performed, based on general relativistic neutrino radiation hydrodynamics in spherical symmetry, in order to explore the previously reported supernova explosion scenario within this class of phenomenological modified microscopic hadronic EOS. A burst-like neutrino signature is released, substantially longer than previously reported based on common hadron-quark hybrid model EOS with two-phase approach and Gibbs phase-transition construction, as observable signal, which is complemented by a gravitational wave mode analysis.

astro-ph.HE↗

arXiv2026

New constraints on non-unitary neutrino mixing from 8 years of IceCube DeepCore atmospheric neutrino data

The mixing between flavor and mass eigenstates of active neutrinos is described by a $3\times3$ unitary matrix. However, the presence of additional heavy sterile neutrino states can lead to a non-unitary neutrino mixing scenario. Atmospheric neutrinos, with their wide range of baselines and energies, provide an excellent probe of such effects. In particular, Earth matter effects in neutrino oscillations play an important role, as the neutral-current potential contributes non-trivially in the presence of non-unitarity. In this work, we use 8 years of publicly available atmospheric neutrino data of IceCube DeepCore to probe this non-unitary neutrino mixing scenario. This high-purity $\nu_\mu$ CC sample provides strong sensitivity, especially to the non-unitary parameters appearing at leading order in the $\nu_\mu \rightarrow \nu_\mu$ channel. The data sample is found to be consistent with the standard unitary mixing framework with no significant deviation. Using this data sample, we place the most stringent bound to date of $\alpha_{33} > -0.027$ at 90% CL, while the other non-unitary parameters are constrained at competitive levels.

hep-ph↗

arXiv2026

Constraints on long-range neutrino interactions from a variety of $U(1)^\prime$ symmetries using atmospheric neutrinos at IceCube DeepCore

Neutrino oscillation experiments provide a unique probe to search for the physics beyond the Standard Model. In this work, we search for a broad class of anomaly-free flavor-dependent $U(1)^\prime$ symmetries using atmospheric neutrino data for the first time. Gauging these $U(1)^\prime$ symmetries give rise to ultra-light vector gauge bosons mediating long-range interactions (LRI) of neutrinos. These new interactions are sourced by the matter present in local and distant Universe, which can affect oscillations of neutrinos passing through the Earth. We use 8 years of high-purity $\nu_\mu$ charged-current neutrino events from IceCube DeepCore to search for these new interactions. We find no evidence for such new interactions in the data sample and place stringent constraints on the corresponding LRI potentials. These results are also translated as the bounds on the coupling strength and mass of mediator over their wide ranges for a plethora of $U(1)^\prime$ symmetries.

hep-ph↗

arXiv2026

Charged-current neutrino opacity within the relativistic Hartree-Fock framework for astrophysical simulations of core-collapse supernovae and binary neutron star mergers

Neutrinos and their weak interactions play a vital role in the physics of core-collapse supernovae and binary neutron star mergers. Their description within astrophysical simulations, including the weak rates, is of pivotal importance not only for the prediction of accurate neutrino fluxes and spectra, including the associated conditions relevant to nucleosynthesis, neutrinos are also responsible for heating and cooling of the stellar plasma as well as the transport of lepton number and entropy. In the present article, we develop an essential improvement of the description of the underlying nuclear medium, necessary for the calculations of charged-current weak rates, with the inclusion of explicitly momentum-dependent nuclear interactions. To this end, we introduce the relativistic Hartree-Fock (RHF) approach and the associated momentum-dependent nucleon self-energies. We discuss the resulting neutrino and antineutrino opacities and find large discrepancies comparing the weak rates at the RHF level with those of commonly used relativistic mean-field (RMF) models; in particular, we observe a substantial shift of previously reported large medium-dependent modifications associated with the RMF approach.

astro-ph.HE↗

arXiv2026

2N and 3N Tensor Force in the $N=34$ Shell Evolution: An Ab Initio Perspective

Shell evolution plays a vital role in understanding the nuclear shell structures across the nuclear chart. In this work, we have investigated the $N = 34$ shell structure using the state-of-the-art ab-initio valence-space in-medium similarity renormalization (VS-IMSRG) approach. Notably, we employ nucleon-nucleon (NN) and three-nucleon (3N) interactions derived from chiral effective field theory and make use of the spin-tensor decomposition scheme to examine the contributions of individual interaction components. We discuss the evolution of the shell structures, which have been investigated by considering the roles of various components, including central, spin-orbit, and tensor effects of NN and 3N forces, respectively. The $N=34$ shell gap gradually decreases from $^{54}$Ca as the proton occupancy in the $\pi{0f_{7/2}}$ orbital increases, and eventually disappears in the $^{62}$Ni as a consequence of the tensor-force driven shell evolution. Our analysis reveals that this disappearance is predominantly governed by the NN tensor force, which accounts for approximately 83$\%$, while the 3N tensor force also contributes about 17$\%$.

nucl-th↗

arXiv2026

Modeling large glitches with core superfluidity in a Hybrid star

Many pulsars exhibit a peculiar behaviour in their pulse profile of a sudden increase in their rotational period, which is popularly known as a pulsar glitch. Some of them show giant glitches with relative amplitude $\Delta\Omega/\Omega \sim 10^{-6}-10^{-5}$. With the model of pinned neutron vortices inside the neutron star (NS) crust, this large glitch cannot be explained so far. However, the increasing evidence of massive pulsars indicates the appearance of exotic degrees of freedom in the inner core of the pulsars. Given this, we consider the pulsar as a hybrid star (HS). This model opens up the possibility of vortex-pinning inside the core. Under the Gibbs equilibrium conditions, it is possible for hadrons and the quark phase to coexist. Due to the global charge neutrality condition, quark pasta structures are formed in the background of hadronic matter. We consider these pasta structures as pinning sites of superfluid vortices. We show that considering the core contribution, our calculations come to be of the order of $\Delta\Omega/\Omega \sim 10^{-6}$, which is close to the observations shown by the Vela-like pulsars.

astro-ph.HE↗

arXiv2026

$\delta_{CP}$-free constraints on NSI parameters $\varepsilon_{e\mu}$ and $\varepsilon_{e\tau}$ using high-purity $\nu_\mu$ CC events at IceCube DeepCore

Atmospheric neutrinos provide a unique avenue to probe theories beyond the Standard Model (BSM) over a wide range of energies and path lengths. The theory of nonstandard interactions (NSI) of neutrinos is one of the important BSM scenarios, which can modify flavor oscillations of atmospheric neutrinos traveling through the Earth. In this work, we use a high-purity $\nu_{\mu}$ charged-current (CC) sample of atmospheric neutrinos from IceCube DeepCore with a livetime of 7.5 years to search for the NSI parameters $\varepsilon_{e\mu}$, $\varepsilon_{e\tau}$, and $\varepsilon_{ee}-\varepsilon_{\mu\mu}$. The $\nu_{\mu}$ CC events mainly come from the $\nu_{\mu}$ survival channel having no significant dependence on $\delta_{CP}$. Therefore, the constraints on $\varepsilon_{e\mu}$ and $\varepsilon_{e\tau}$ obtained using this $\nu_{\mu}$ CC sample are expected to be free from the $\delta_{CP}$-degeneracy. The data sample is found to be in agreement with the standard neutrino interactions. Therefore, we place bounds on these NSI parameters that are consistent with and comparable to existing experimental constraints. These $\delta_{CP}$-free constraints from IceCube DeepCore are complementary to those from the long-baseline neutrino oscillation experiments, where the appearance channel depends on $\delta_{CP}$.

hep-ph↗

arXiv2026

Dynamics-induced activity patterns of active-inactive clusters in complex networks

Synchrony patterns describe network states in which nodes of a coupled dynamical system are grouped into clusters based on synchronization between nodes. Beyond simple synchrony, synchronized clusters may also exhibit active or inactive states, and the collection of all such clusters constitutes an activity pattern. Although these patterns may arise naturally in networks with permutation symmetries, the requirement of symmetries imposes a restrictive and often unrealistic assumption, as many real-world networks lack such symmetries. In this work, we present synchrony patterns of coexisting active-inactive clusters that cannot be identified through symmetries. Considering dynamical systems in which intrinsic dynamics and coupling functions are odd functions in phase space, we identify all possible patterns a network can exhibit through symmetry breaking of identically synchronized clusters. The symmetry breaking of invariant clusters generates antisynchronized clusters, allowing active-inactive clusters to coexist. We show that while active clusters are external equitable partitions, inactive clusters can be purely dynamics-induced. Starting with a symmetry-broken state, we show that the existence of different invariant patterns is a function of coupling strength and intercluster weights. Finally, by combining synchronization manifolds with the Laplacian eigenvectors, we identify transversal perturbations for these patterns and present a stability analysis.

nlin.AO↗

arXiv2026

Kondo driven suppression of charge density wave in Van der Waals material UTe$_3$

Competing electronic instabilities lie at the heart of emergent phenomena in quantum materials. In low-dimensional metals, Fermi-surface nesting can drive charge density wave (CDW) formation through a Peierls-like mechanism, while in strongly correlated systems, Kondo hybridization reconstructs the electronic structure by entangling localized moments with itinerant electrons. How these two fundamentally different instabilities interact$-$whether they coexist, compete, or mutually exclude each other$-$remains an open question. Here, we present suppression of charge density wave via the Kondo interaction in van der Waals material UTe$_3$. The angle-resolved photoemission spectroscopy (ARPES) data reveals Fermi surface nesting under similar conditions as seen in RETe$_3$ compounds. Despite that, no CDW is found in UTe$_3$ after an extensive search. We demonstrate that strong hybridization between U 5$f$ electrons and Te $p$ states reconstructs the low-energy electronic structure, removes the instability, and preempts CDW formation. Our results reveal a rare example where Kondo hybridization preempts density wave formation, offering a new route to controlling ordering phenomena in correlated 2D materials.

cond-mat.str-el↗

arXiv2026

First Constraints on Long-Range Neutrino Interactions using IceCube DeepCore

We present the first search for new flavor-dependent long-range interactions (LRI) of neutrinos using publicly available 8 years of high-purity $\nu_\mu$ CC data from IceCube DeepCore. These interactions are mediated by ultra-light gauge bosons with masses below $10^{-10}$ eV, which can arise due to a new lepton-number gauge symmetry, such as $L_e - L_\mu$ or $L_e - L_\tau$. These long-range interactions induce matter potential between neutrinos and abundant electrons present in distant astrophysical sources. These LRI potentials could modify neutrino oscillation probabilities. By probing the effects of LRI on atmospheric neutrino oscillations at IceCube DeepCore, we place world-leading constraints on the coupling strength of these interactions.

hep-ph↗

arXiv2025

Modulation of quantum geometry and its coupling to pseudo-electric field by dynamic strain

Two-dimensional materials are a fertile ground for exploring quantum geometric phenomena, with Berry curvature and its first moment, the Berry curvature dipole, playing a central role in their electronic response. These geometric properties influence electronic transport and result in the anomalous and nonlinear Hall effects, and are typically controlled using static electric fields or strain. However, the possibility of modulating quantum geometric quantities in real-time remains unexplored. Here, we demonstrate the dynamic modulation of Berry curvature and its moments, as well as the generation of a pseudo-electric field using time-dependent strain. By placing heterostructures on a membrane, we introduce oscillatory strain together with an in-plane AC electric field and measure Hall signals that are modulated at linear combinations of the frequencies of strain and electric field. Our measurements reveal modulation of Berry curvature and its first moment. Notably, we provide direct experimental evidence of pseudo-electric field that results in an unusual dynamic strain-induced Hall response. This approach opens up a new pathway for controlling quantum geometry on demand, moving beyond conventional static perturbations. The pseudo-electric field provides a framework for external electric field-free anomalous Hall response and opens new avenues for probing the topological properties.

cond-mat.mes-hall↗

arXiv2025

Stringent constraints on non-standard neutrino interactions using high-purity $\nu_{\mu}$ CC events in IceCube DeepCore

The neutral-current (NC) non-standard interactions (NSI) of neutrinos with fermions can modify the flavor oscillations of atmospheric neutrinos as they propagate through the Earth. We present constraints on the NC-NSI parameters $\varepsilon_{\mu\tau}$ and $\varepsilon_{\tau\tau}-\varepsilon_{\mu\mu}$ (one at a time) using a high-purity sample of $\nu_{\mu}$ charged-current (CC) atmospheric neutrino events collected by IceCube DeepCore over 7.5 years of livetime. These two parameters significantly affect the $\nu_\mu$ disappearance channel for which this golden event sample is optimized by the IceCube Collaboration. The best fit to this dataset is consistent with no NSI hypothesis, and we place the most stringent constraints to date: $-\,0.0094 < \varepsilon_{\mu\tau} < 0.0079$ and $-\,0.030 < \varepsilon_{\tau\tau}-\varepsilon_{\mu\mu} < 0.029$ at 90% confidence level.

hep-ph↗

arXiv2025

Real-Time Cooked Food Image Synthesis and Visual Cooking Progress Monitoring on Edge Devices

Synthesizing realistic cooked food images from raw inputs on edge devices is a challenging generative task, requiring models to capture complex changes in texture, color and structure during cooking. Existing image-to-image generation methods often produce unrealistic results or are too resource-intensive for edge deployment. We introduce the first oven-based cooking-progression dataset with chef-annotated doneness levels and propose an edge-efficient recipe and cooking state guided generator that synthesizes realistic food images conditioned on raw food image. This formulation enables user-preferred visual targets rather than fixed presets. To ensure temporal consistency and culinary plausibility, we introduce a domain-specific \textit{Culinary Image Similarity (CIS)} metric, which serves both as a training loss and a progress-monitoring signal. Our model outperforms existing baselines with significant reductions in FID scores (30\% improvement on our dataset; 60\% on public datasets)

cs.CV↗

arXiv2025

Symmetry-induced activity patterns of active-inactive clusters in complex networks

Synchrony patterns characterize network states in which nodes organize into clusters based on their synchronized dynamics. The synchronized clusters may further exhibit either active or inactive states. The simultaneous invariance of active and inactive clusters of synchronized nodes poses a dynamical constraint because fluctuations from active clusters must cancel out for a desired cluster to be inactive. By exploiting permutation symmetries in the network structure and choosing dynamics on top such that internal dynamics and coupling functions are odd functions in the phase space, we demonstrate that this combination of structure and dynamics exhibits stable invariant patterns composed of coexisting active and inactive clusters. The symmetries in a network generate active clusters that are in antisynchrony with each other, resulting in the cancellation of fluctuations for clusters connected with these antisynchronous clusters. We use full network symmetries to obtain synchronized clusters, while quotient network symmetries are used to find coexisting active-inactive states of clusters. We show that as the coupling between nodes changes, active clusters lose their activity at different coupling values, and the network transitions from one activity pattern to another. Numerical simulations are presented for networks of Van der Pol and Stuart-Landau oscillators. Finally, we extend the master stability framework to these patterns and provide stability conditions for their existence.

nlin.AO↗