Publications

Order by: publication date number of citations

• Conformal maps and superfluid vortex dynamics on curved and bounded surfaces: The case of an elliptical boundary

  Matteo Caldara, Andrea Richaud, Pietro Massignan, Alexander L. Fetter

  SciPost Phys. 17, 039 (2024) · published 8 August 2024 | Toggle abstract · pdf

  Recent advances in cold-atom platforms have made real-time dynamics accessible, renewing interest in the motion of superfluid vortices in two-dimensional domains. Here we show that the energy and the trajectories of arbitrary vortex configurations may be computed on a complicated (curved or bounded) surface, provided that one knows a conformal map that links the latter to a simpler domain (like the full plane, or a circular boundary). We also prove that Hamilton's equations based on the vortex energy agree with the complex dynamical equations for the vortex dynamics, demonstrating that the vortex trajectories are constant-energy curves. We use these ideas to study the dynamics of vortices in a two-dimensional incompressible superfluid with an elliptical boundary, and we derive an analytical expression for the complex potential describing the hydrodynamic flow throughout the fluid. For a vortex inside an elliptical boundary, the orbits are nearly self-similar ellipses.

• T-odd quark-gluon-quark correlation function in the light-front quark-diquark model

  Shubham Sharma, Narinder Kumar, Harleen Dahiya

  SciPost Phys. Proc. 8, 170 (2022) · published 14 July 2022 | Toggle abstract · pdf

  We have scrutinized the transverse momentum dependent quark-gluon-quark correlation function. We have utilized the light-front quark-diquark model to study the time-reversal-odd interaction-dependent twist-3 gluon distributions which we have obtained from the disintegration of the transverse momentum dependent quark-gluon-quark correlator. Specifically, we have studied the behavior of $\tilde{e}_{L}$ and $\tilde{e}_{T}$ while considering our diquark to be an axial-vector.

• Valence quark distributions of light mesons in light-cone quark model

  Satvir Kaur, Narinder Kumar, Jiangshan Lan, Chandan Mondal, Harleen Dahiya

  SciPost Phys. Proc. 8, 172 (2022) · published 14 July 2022 | Toggle abstract · pdf

  In order to investigate the tomographical structure of light pseudoscalar mesons, particularly, pion and kaon, we study the valence quark distribution function (PDF) and the generalized parton distributions (GPDs) using light-cone quark model (LCQM).

• All fractional Shapiro steps in the RSJ model with two Josephson harmonics

  Pavel N. Tsarev, Yakov V. Fominov

  SciPost Phys. 19, 148 (2025) · published 8 December 2025 | Toggle abstract · pdf

  Synchronization between the internal dynamics of the superconducting phase in a Josephson junction (JJ) and an external ac signal is a fundamental physical phenomenon, manifesting as constant-voltage Shapiro steps in the current-voltage characteristic. Mathematically, this phase-locking effect is captured by the Resistively Shunted Junction (RSJ) model, an important example of a nonlinear dynamical system. The standard RSJ model considers an overdamped JJ with a sinusoidal (single-harmonic) current-phase relation (CPR) in the current-driven regime with a monochromatic ac component. While this model predicts only integer Shapiro steps, the inclusion of higher Josephson harmonics is known to generate fractional Shapiro steps. In this paper, we show that only two Josephson harmonics in the CPR are sufficient to produce all possible fractional Shapiro steps within the RSJ framework. Using perturbative methods, we analyze the amplitudes of these fractional steps. Furthermore, by introducing a phase shift between the two Josephson harmonics, we reveal an asymmetry between positive and negative fractional steps—a signature of the Josephson diode effect.

• Spin degrees of freedom incorporated in conformal group: Introduction of an intrinsic momentum operator

  Seiichi Kuwata

  SciPost Phys. Proc. 14, 034 (2023) · published 24 November 2023 | Toggle abstract · pdf

  Considering spin degrees of freedom incorporated in the conformal generators, we introduce an intrinsic momentum operator $\pi_\mu$, which is feasible for the Bhabha wave equation. If a physical state $\psi_{ph}$ for spin s is annihilated by the $\pi_\mu$, the degree of $\psi_{ph}$, deg $\psi_{ph}$, should equal twice the spin degrees of freedom, $2 ( 2 s + 1)$ for a massive particle, where the multiplicity $2$ indicates the chirality. The relation deg $\psi_{ph}$ = 2(2s+1) holds in the representation $R_5$ (s,s), irreducible representation of the Lorentz group in five dimensions.

• Hierarchy of degenerate stationary states in a boundary-driven dipole-conserving spin chain

  Apoorv Srivastava, Shovan Dutta

  SciPost Phys. 18, 111 (2025) · published 27 March 2025 | Toggle abstract · pdf

  Kinetically constrained spin chains serve as a prototype for structured ergodicity breaking in isolated quantum systems. We show that such a system exhibits a hierarchy of degenerate steady states when driven by incoherent pump and loss at the boundary. By tuning the relative pump and loss and how local the constraints are, one can stabilize mixed steady states, noiseless subsystems, and various decoherence-free subspaces, all of which preserve large amounts of information. We also find that a dipole-conserving bulk suppresses current in steady state. These exact results based on the flow in Hilbert space hold regardless of the specific Hamiltonian or drive mechanism. Our findings show that a competition of kinetic constraints and local drives can induce different forms of ergodicity breaking in open systems, which should be accessible in quantum simulators.

• Dark matter searches and energy accumulation and release in materials

  Sergey Pereverzev

  SciPost Phys. Proc. 12, 009 (2023) · published 3 July 2023 | Toggle abstract · pdf

  Efforts to identify dark matter by detecting nuclear recoils produced by dark matter particles reveal low-energy backgrounds of unknown origin in different types of detectors. In many cases, energy accumulation and delayed burst-like releases of stored energy could provide an explanation. These dynamics follow Prigogine's ideas on systems with energy flow and the general Self-Organized Criticality scenario. We compare these models with properties of excess backgrounds in cryogenic solid-state detectors, relaxation processes in glasses and crystals, our observations of delayed luminescence in NaI(Tl), and make predictions for more phenomena present in these systems and in superconducting photon detectors and qubits. Experiments to create accurate phenomenological models are needed.

• Multiscale response of ionic systems to a spatially varying electric field

  Jesper Schmidt Hansen

  SciPost Phys. 2, 017 (2017) · published 27 May 2017 | Toggle abstract · pdf

  In this paper the response of ionic systems subjected to a spatially varying electric field is studied. Following the Nernst-Planck equation, two forces driving the mass flux are present, namely, the concentration gradient and the electric potential gradient. The mass flux due to the concentration gradient is modelled through Fick's law, and a new constitutive relation for the mass flux due to the potential gradient is proposed. In the regime of low screening the response function due to the potential gradient is closely related to the ionic conductivity. In the large screening regime, on the other hand, the response function is governed by the charge-charge structure. Molecular dynamics simulations are conducted and the two wave vector dependent response functions are evaluated for models of a molten salt and an ionic liquid. In the low screening regime the response functions show same wave vector dependency, indicating that it is the same underlying physical processes that govern the response. In the screening regime the wave vector dependency is very different and, thus, the overall response is determined by different processes. This is in agreement with the observed failure of the Nernst-Einstein relation.

• Influence of the Pauli principle on two-cluster potential energy

  Yuliya A. Lashko, Victor S. Vasilevsky, Gennady F. Filippov

  SciPost Phys. Proc. 3, 021 (2020) · published 25 February 2020 | Toggle abstract · pdf

  We study effects of the Pauli principle on the potential energy of two-cluster systems. The object of the investigation is the lightest nuclei of p-shell with a dominant $\alpha$-cluster channel. For this aim we construct matrix elements of two-cluster potential energy between cluster oscillator functions with and without full antisymmetrization. Eigenvalues and eigenfunctions of the potential energy matrix are studied in detail. Eigenfunctions of the potential energy operator are presented in oscillator, coordinate and momentum spaces. We demonstrate that the Pauli principle affects more strongly the eigenfunctions than the eigenvalues of the matrix and leads to the formation of resonance and trapped states.

• On irregularities in the cosmic ray spectrum of \(10^{16}-10^{18}\) eV range

  Stanislav P. Knurenko, Igor S. Petrov

  SciPost Phys. Proc. 13, 020 (2023) · published 28 September 2023 | Toggle abstract · pdf

  Existing small, medium and large arrays for the study of cosmic rays of ultra-high energies are aimed for obtaining information about our galaxy and extragalactic space, namely to search and study astronomical objects that produce the flux of relativistic particles. The drift and interaction of such particles with magnetic fields and shock waves taking place in interstellar space causes the same interest. The shape of the energy spectrum of cosmic rays in the energy range $10^{15}-10^{18}$ eV, where the "knee" and the "second knee" are observed, can be formed as a superposition of the partial spectra of various chemical elements. Verification of galactic models, using recent experimental spectral data, makes it possible to study the nature of the galactic and extragalactic components of cosmic rays. The paper presents the result of the energy spectrum of cosmic rays in the range $10^{16}-10^{18}$ eV of measurements obtained with the Small Cherenkov array - a part of the Yakutsk array.