arXiv subjects

Rishabh Sharma

Publications and source records attributed to Rishabh Sharma.

At least 19 recordsLinked to original sources

arXiv2026

Functional H_infinity Filtering for Descriptor Systems with Incrementally Quadratic Nonlinearities under Disturbances

This paper develops a functional H_infinity filter for nonlinear descriptor systems subject to external disturbances. Conventional H_infinity filtering approaches for descriptor systems impose restrictive regularity assumptions and employ implicit descriptor-form filters, leading to practical implementation difficulties. Moreover, existing approaches mainly target full-or reduced-order state estimation, which is computationally inefficient when only a specific functional of the state is required. To address these limitations, the filter is formulated directly in an explicit state-space framework and can be initialized with arbitrary initial values. The filter order is chosen to be less than or equal to the dimension of the functional vector to be estimated, thereby reducing computational complexity. The considered nonlinearities are characterized using incremental quadratic constraints parameterized by appropriate multiplier matrices, which encompass Lipschitz, one-sided Lipschitz, monotone, and many other nonlinearities. Sufficient criteria for the existence of the proposed filter are established through a rank condition imposed on the system matrices together with a set of linear matrix inequalities (LMIs). Under these conditions, asymptotic stability of the estimation error dynamics is guaranteed, while the influence of external disturbances on the error is bounded within a prescribed L2-performance framework. Finally, numerical simulations demonstrate and validate the effectiveness of our theoretical results.

math.OC↗

arXiv2026

Cyclic Denoising Reveals Ultrastable Memories in Diffusion Models

We introduce cyclic denoising -- repeated forward and reverse diffusion at controlled noise amplitudes -- as an extraction attack for image diffusion models. Inspired by random organization in disordered solids, cyclic denoising exposes regions of the learned distribution that are largely inaccessible to standard sampling. The dynamics drive samples toward attractors with a broad stability spectrum. The deepest attractors are ultrastable: they regenerate after near-total corruption and persist through thousands of noising-denoising cycles. Many of these attractors correspond to memorized training images, including stock photographs, brand watermarks, and web-crawl artifacts. The attack requires only sampler-level control, with no gradients, weight inspection, prompts, captions, or prior knowledge of the training data. Unlike generate-and-filter attacks, which rely on large-scale prompted generation and post-hoc similarity or membership-inference filtering, our main protocol is fully unconditioned. We demonstrate the phenomenon in Stable Diffusion v1.4 and in a pixel-space DDPM, showing consistent behavior across latent- and pixel-space diffusion models. Across noise amplitudes, we observe a yielding-like transition: low-amplitude cycling produces trivial absorbing fixed points or limit cycles, while larger amplitudes induce rearrangements, basin hopping, and long-lived trapping in structured memorized attractor basins. We also observe hierarchical partial absorption, prompt-stabilized basins, and cross-initial-condition universality of the recovered attractor set. Our results therefore show that cyclic denoising is both a physics-inspired probe of generative landscapes and a practical tool for memorization auditing, with implications for privacy, copyright compliance, and model fingerprinting.

cs.LG↗

arXiv2026

Hard to See, Hard to Label: Generative and Symbolic Acquisition for Subtle Visual Phenomena

Subtle visual anomalies such as hairline cracks, sub-millimeter voids, and low-contrast inclusions are structurally atypical yet visually ambiguous, making them both difficult to annotate and easy to overlook during active learning. Standard acquisition heuristics based on discriminative uncertainty or feature diversity often overselect dominant patterns while underexploring sparse yet important regions of the data space. This failure mode is especially severe in industrial defect inspection, where anomalies may be both low-prevalence and difficult to distinguish from surrounding structure. To resolve this, we propose GSAL, an active learning framework for object detection that combines a diffusion-based difficulty signal with a hierarchical semantic coverage prior. The diffusion component scores images and proposals using reconstruction discrepancy and denoising variability, prioritizing visually atypical or ambiguous examples. However, diffusion alone does not prevent acquisition from repeatedly favoring hard samples within dominant semantic modes. The semantic component therefore organizes candidate samples in a three-level concept graph and promotes coverage of underrepresented semantic regions while providing interpretable acquisition rationales. By balancing visual difficulty with semantic coverage, GSAL improves retrieval of subtle and rare targets that are often missed by uncertainty-only selection. Experiments on a proprietary thin-film defect, Pascal VOC and MS COCO dataset show consistent gains in label efficiency and rare-class retrieval over uncertainty-, diversity-, and hybrid-based baselines

cs.CV↗

arXiv2026

Inertial effects on flow dynamics near a moving contact line

This study investigates the role of inertia in moving contact lines using experiments, theoretical analysis, and numerical simulations. Experiments are conducted using a plate immersion configuration over a wide range of Reynolds numbers from $O(10^{-3})$ to $O(10)$. Flow configurations and quantitative measurements are obtained using high-speed imaging and particle image velocimetry. The streamfunction contours reconstructed from the experimental velocity fields are compared with the viscous modulated wedge solution (viscous-MWS) and inertial-MWS theory. Experimental observations show that the streamfunction contours agree well with viscous predictions at low Reynolds numbers; however, systematic deviations emerge as the Reynolds number increases. The inertial-MWS theory, an inertial extension of the Huh and Scriven framework, accounts for these deviations, but only within a narrow range of Reynolds numbers $10^{-1} < Re < 1$. At higher Reynolds numbers, inertial theory fails to accurately capture the deviations in the streamfunction contours observed in the experiments. Moreover, simulations conducted using the volume of fluid method support our findings, exhibiting deviations in streamfunction contours consistent with experimental observations. We demonstrate that inertia does not fundamentally alter the underlying flow configuration but instead induces a systematic deviation in the streamfunction contours. At finite $Re$, the interfacial speed transitions from a nearly constant value in the viscous regime to a monotonic decay along the interface. These findings expose the need for more sophisticated models of moving contact lines.

physics.flu-dyn↗

arXiv2026

Cross-View World Models

World models enable agents to plan by imagining future states, but existing approaches operate from a single viewpoint, typically egocentric, even when other perspectives would make planning easier; navigation, for instance, benefits from a bird's-eye view. We introduce Cross-View World Models (XVWM), trained with a cross-view prediction objective: given a sequence of frames from one viewpoint, predict the future state from the same or a different viewpoint after an action is taken. Enforcing cross-view consistency acts as geometric regularization: because the input and output views may share little or no visual overlap, to predict across viewpoints, the model must learn view-invariant representations of the environment's 3D structure. We train on synchronized multi-view gameplay data from Aimlabs, an aim-training platform providing precisely aligned multi-camera recordings with high-frequency action labels. The resulting model gives agents parallel imagination streams across viewpoints, enabling planning in whichever frame of reference best suits the task while executing from the egocentric view. Our results show that multi-view consistency provides a strong learning signal for spatially grounded representations. Finally, predicting the consequences of one's actions from another viewpoint may offer a foundation for perspective-taking in multi-agent settings.

cs.CV↗

arXiv2026

Exploring the properties of the Hadronic Phase in Heavy-Ion Collisions at RHIC Energies via Partial Chemical Equilibrium

The hadronic phase in heavy-ion collisions plays a crucial role in shaping the final-state hadron abundances. In this work, we study Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7-200 GeV using the Hadron Resonance Gas model in Partial Chemical Equilibrium (HRG-PCE). By fitting the yields of stable hadrons and short-lived resonances such as K$^*(892)^0$, we extract both chemical and kinetic freeze-out temperatures as functions of center-of-mass energy and centrality. The analysis, performed using the Thermal-FIST package, avoids assumptions about radial flow profile or freeze-out hypersurfaces. Furthermore, we estimate the baryon annihilation freeze-out temperature from the experimentally measured $\bar{\rm p}/$p ratio, using the HRG-PCE framework extended to include $B\bar{B} \leftrightarrow n\pi$ reactions. The inferred annihilation freeze-out temperature lies between the chemical and kinetic freeze-out temperatures, suggesting that baryon annihilation remains active in the early hadronic phase but ceases prior to kinetic freeze-out. These results provide a consistent picture of the sequential decoupling of hadronic processes and demonstrate that inelastic hadronic interactions significantly influence the chemical composition of the system between chemical and kinetic freeze-outs at RHIC energies.

nucl-th↗

arXiv2025

Towards compressed baryonic matter densities: thermodynamics and transport coefficients

We study the thermodynamic and transport properties of hot and dense quantum chromodynamic matter expected to be produced in low-energy heavy-ion collisions, using three different effective quantum chromodynamic frameworks: the Nambu--Jona-Lasinio model, the chiral effective model, and the hadron resonance gas model. We briefly outline the theoretical formulation of thermodynamic quantities and transport coefficients within these approaches, where quarks are treated with effective masses in the Nambu--Jona-Lasinio and chiral effective models, and hadronic degrees of freedom are employed in the hadron resonance gas model. The transport coefficients are evaluated using the Boltzmann transport equation in the relaxation-time approximation. Following the theoretical overview, we present a comprehensive analysis of the behavior of these quantities as functions of the baryon chemical potential or net baryon density. The Lorenz ratio $\kappa/(\sigma T)$ is found to increase rapidly-indicating a strong violation of the Wiedemann-Franz law in the low-$\mu_{B}$ regime--while approaching the universal value at higher baryon chemical potentials or densities. The shear-viscosity-to-entropy-density ratio $\eta/s$ remains nearly constant at low $\mu_{B}$ but exhibits a gradual increase as $\mu_{B}$ grows. We also discuss the qualitative similarities of these trends with those observed in the electron-hole plasma of graphene, an emergent quasi-relativistic system characterized by massless energy-momentum dispersion.

nucl-th↗

arXiv2024

Flavour-Dependent Chemical Freeze-Out of Light Nuclei in Relativistic Heavy-Ion Collisions

We study the production of light nuclei in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7 - 200 GeV and Pb+Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 2.76 and 5.02 TeV within a flavour-dependent freeze-out framework, assuming different flavoured hadrons undergo separate chemical freeze-out. Using the Thermal-FIST package, thermal parameters extracted from fits to various sets of hadron yields, including and excluding light nuclei, are used to calculate the ratios of the yields of light nuclei, namely, $d/p$, $\bar{d}/\bar{p}$, $t/p$, and $t/d$. A comparison with data from the STAR and ALICE collaborations shows that a sequential freeze-out scenario provides a better description of light nuclei yield ratios than the traditional single freeze-out approach. These results suggest the flavour-dependent chemical freeze-out for final state light-nuclei production persists in heavy-ion collisions at both RHIC and LHC energies.

hep-ph↗

arXiv2024

Dynamics of Hot QCD Matter 2024 -- Hard Probes

The hot and dense QCD matter, known as the Quark-Gluon Plasma (QGP), is explored through heavy-ion collision experiments at the LHC and RHIC. Jets and heavy flavors, produced from the initial hard scattering, are used as hard probes to study the properties of the QGP. Recent experimental observations on jet quenching and heavy-flavor suppression have strengthened our understanding, allowing for fine-tuning of theoretical models in hard probes. The second conference, HOT QCD Matter 2024, was organized to bring the community together for discussions on key topics in the field. This article comprises 15 sections, each addressing various aspects of hard probes in relativistic heavy-ion collisions, offering a snapshot of current experimental observations and theoretical advancements. The article begins with a discussion on memory effects in the quantum evolution of quarkonia in the quark-gluon plasma, followed by an experimental review, new insights on jet quenching at RHIC and LHC, and concludes with a machine learning approach to heavy flavor production at the Large Hadron Collider.

nucl-ex↗

arXiv2024

Heavy quarkonium dissociation in the presence of magnetic field and anisotropy using dissociation energy criterion

In this article, we have studied the dissociation temperature of 1S and 2S states of heavy quarkonium in the presence of anisotropy and a strong magnetic field background using the dissociation energy criterion. We utilized the medium-modified form of the Cornell potential, which depends on temperature as well as the anisotropic parameter {\xi} and the magnetic field. The binding energy (B.E.) and dissociation energy (D.E.) of heavy quarkonium have been examined for different values of the magnetic field and anisotropy. It is noted that B.E. starts decreasing from higher values as we increase the anisotropy, while D.E. exhibits the opposite behavior. The dissociation temperature appears to increase with anisotropy, while it decreases with the magnetic field, as shown in Table 1 and 2 respectively. These results align well with recent research findings.

hep-ph↗

arXiv2024

Functional H_infity Filtering for Descriptor Systems with Monotone nonlinearities

This paper introduces a novel approach to design of functional H_\infty filters for a class of nonlinear descriptor systems subjected to disturbances. Departing from conventional assumptions regarding system regularity, we adopt a more inclusive approach by considering general descriptor systems that satisfy a rank condition on their coefficient matrices. Under this rank condition, we establish a linear matrix inequality (LMI) as a sufficient criterion ensuring the stability of the error system and constraining the L 2 gain of the mapping from disturbances to errors to a predetermined level. The efficacy of the proposed approach is demonstrated through a practical example involving a simple constrained mechanical system.

math.OC↗

arXiv2024

Study of Heavy Quarkonia in the presence of magnetic field by Nikiforov Uvarov method

The N-dimensional radial Schrodinger equation has been solved using the Nikiforov Uvarov (NU) method, in which we used the medium modified form of Cornell potential and quasi-particle Debye mass with strong magnetic field background. The binding energies and the mass spectra of heavy quarkonium have been studied in the N-dimensional space for different values of magnetic field, the binding energy decreases with increasing magnetic field, which shows early dissociation of heavy quarkonium system. The influence of dimensionality number has also been discussed on binding energies of J/ψ and Υ for fixed value of magnetic field. It is found that with an increase in dimensionality, the binding energy starts decreasing from a higher initial value. The results obtained are quite consistent with recent studies.

hep-ph↗

arXiv2024

Loading a quantum gas from a hybrid dimple trap to a shell trap

Starting from a degenerate Bose gas in a hybrid trap combining a magnetic quadrupole trap and an attractive optical trap resulting from a focused laser beam, we demonstrate the efficient loading of this quantum gas into a shell-shaped trap. The shell trap is purely magnetic and relies on adiabatic potentials for atoms in an inhomogeneous magnetic field dressed by a radiofrequency (rf) field. We show that direct rf evaporation in the hybrid trap enables an efficient and simple preparation of the cold sample, well adapted to the subsequent loading procedure. The transfer into the shell trap is adiabatic and limits the final excitation of the center-of-mass motion to below 2 micrometres.

cond-mat.quant-gas↗

arXiv2024

Thermal melting of a vortex lattice in a quasi two-dimensional Bose gas

We report the observation of the melting of a vortex lattice in a fast rotating quasi-two dimensional Bose gas, under the influence of thermal fluctuations. We image the vortex lattice after a time-of-flight expansion, for increasing rotation frequency at constant atom number and temperature. We detect the vortex positions and study the order of the lattice using the pair correlation function and the orientational correlation function. We evidence the melting transition by an abrupt change in the decay of orientational correlations, associated to a proliferation of dislocations. Our findings are consistent with the hexatic to liquid transition in the KTHNY scenario for two-dimensional melting.

cond-mat.quant-gas↗

arXiv2024

System size dependence of thermodynamic variables at kinetic freeze-out in high-energy collisions using the Tsallis distribution

We use a thermodynamically consistent form of Tsallis distribution to study the dependence of various thermodynamic quantities on the system size in high-energy collisions. The charged hadron spectra obtained in $p$+$p$, $p$+Pb, Xe+Xe, and Pb+Pb collisions at LHC are used to determine the energy density, pressure, particle density, entropy density, mean free path, Knudsen number, heat capacity, isothermal compressibility, expansion coefficient, and speed of sound at the kinetic freeze-out surface. These quantities are studied as a function of the system size. Notably, the rate of increase (or decrease) in these thermodynamic variables is found to be more rapid in small systems such as $p$+$p$ and $p$+Pb collisions than in large systems such as Xe+Xe and Pb+Pb collisions. This may be due to the small volume of the hadronic system in small collision systems at kinetic freeze-out. It is observed that high-multiplicity $p$+$p$ collisions produce similar thermodynamic conditions as peripheral heavy-ion collisions at kinetic freeze-out.

hep-ph↗

arXiv2023

Elliptic and triangular flow of light nuclei in Au+Au collisions in the BES-II energies using the STAR detector

Light nuclei might be formed in heavy-ion collisions by the coalescence of produced (anti-)nucleons or transported nucleons. Due to their low binding energies, they are more likely to form at later stages of the hadronic fireball. In this proceedings, we report the transverse momentum and centrality dependence of elliptic ($v_{2}$) and triangular ($v_{3}$) flow of $d$, $t$, and $^3$He in Au+Au collisions at $\sqrt{s_{NN}}$ = 14.6 -- 54.4 GeV. The mass number scaling of $v_{2}(p_{T})$ and $v_{3}(p_{T})$ of light nuclei is discussed. We also report the comparison of $v_{2}(p_{T})$ and $v_{3}(p_{T})$ of light nuclei with a transport-plus-coalescence model calculation.

nucl-ex↗

arXiv2023

Dissociation and thermodynamical properties of heavy quarkonia in an anisotropic strongly coupled hot QGP: using baryonic chemical potential

We extended the recent work Phys. Rev. D 97(9), 094033 (2018) to investigate quarkonium dissociation in presence of baryonic chemical potential (mu_b) and anisotropy (ξ) using quasi-particle approach in hot quantum chromodynamics (QCD) medium. We have determined binding energy and thermal width of S-states of charmonia and bottomonia for n=1 and n=2 (radial quantum number) with anisotropic parameter (ξ) and baryonic chemical potential. We have also determined the effects of baryonic chemical potential and anisotropy on mass spectra of 1S-states of quarkonia and the results obtained were consistent with theoretical and experimental works. But the key result obtained was dissociation temperature of the S-states with the effect of {mu_b} and ξ. At last, we have calculated the thermodynamical properties of QGP (i.e., pressure, energy density and speed of sound) using the parameter ξ and {mu_b}, which is the main key to study suppression of the quarkonium with latest determined value of energy density psNN after incorporating the effect of ξ and (mu_b).

hep-ph↗

arXiv2023

Study of Quarkonium properties using SUSYQM method with baryonic chemical potential

In this article, we employed the Quasi-particle debye mass at finite baryonic chemical potential which can be used in the medium modified heavy quark potential to solve the N-dimensional Schroedinger equation. The bound state solution of the Schroedinger equation using Cornell potential is obtained by Super-Symmetry Quantum Mechanics (SUSYQM) method. The thermodynamical properties of quark matter is calculated by using baryonic chemical potential (mu). We found that the binding energy of quarkonia dissociates more with quasi-particle debye mass in comparison to non-perturbative and leading order debye mass. The medium modified form of potential (real part) has been used to study the thermodynamical properties of quark matter with different equation of states (EoS) (i.e., pressure, energy density and speed of sound) with {mu}. The mass spectra of quarkonia has been also calculated in the N-dimensional space, and compared with the experimental data at N=3. We have also calculated the dissociation temperature (T_D) for the ground states of quarkonium using the dissociation criteria of thermal width.

hep-ph↗