Publications

Order by: publication date number of citations

• Prethermalization in coupled one-dimensional quantum gases

  Maciej Łebek, Miłosz Panfil, Robert M. Konik

  SciPost Phys. 17, 007 (2024) · published 10 July 2024 | Toggle abstract · pdf

  We consider the problem of the development of steady states in one-dimensional Bose gas tubes that are weakly coupled to one another through a density-density interaction. We analyze this development through a Boltzmann collision integral approach. We argue that when the leading order of the collision integral, where single particle-hole excitations are created in individual gases, is dominant, the state of the gas evolves first to a non-thermal fixed point, i.e. a prethermalization plateau. This order is dominant when a pair of tubes are inequivalent with, say, different temperatures or different effective interaction parameters, $\gamma$. When both tubes are in the strongly interacting regime we additionally characterize this non-thermal prethermalization plateau by constructing the quasi-conserved quantities that control the existence of this plateau as well as the associated generalized Gibbs ensemble.

  2 citations

• Interfacially adsorbed bubbles determine the shape of droplets

  Alessio Squarcini, Antonio Tinti

  SciPost Phys. 15, 164 (2023) · published 16 October 2023 | Toggle abstract · pdf

  The characterization of density correlations in the presence of strongly fluctuating interfaces has always been considered a difficult problem in statistical mechanics. Here we study - by using recently developed exact field-theoretical techniques - density correlations for an interface with endpoints on a wall forming a droplet in 2D. Our framework applies to interfaces entropically repelled by a hard wall as well as to wetting transitions. In the former case bubbles adsorbed on the interface are taken into account by the theory which yields a systematic treatment of finite-size corrections to one- and two-point functions and show how these are related to Brownian excursions. Our analytical predictions are confirmed by Monte Carlo simulations without free parameters. We also determine one- and two-point functions at wetting by using integrable boundary field theory. We show that correlations are long ranged for entropic repulsion and at wetting. For both regimes we investigate correlations in momentum space by generalizing the notion of interface structure factor to semi-confined systems. Distinctive signatures of the two regimes manifest in the structure factor through a term that we identify on top of the capillary-wave one.

  2 citations

• Microscopic derivation of Ginzburg-Landau theories for hierarchical quantum Hall states

  Yoran Tournois, Maria Hermanns, Thors Hans Hansson

  SciPost Phys. 8, 079 (2020) · published 18 May 2020 | Toggle abstract · pdf

  We propose a Ginzburg-Landau theory for a large and important part of the abelian quantum Hall hierarchy, including the prominently observed Jain sequences. By a generalized "flux attachment" construction we extend the Ginzburg-Landau-Chern-Simons composite boson theory to states obtained by both quasielectron and quasihole condensation, and express the corresponding wave functions as correlators in conformal field theories. This yields a precise identification of the relativistic scalar fields entering these correlators in terms of the original electron field.

  2 citations

• Adiabatic deformations of quantum Hall droplets

  Blagoje Oblak, Benoit Estienne

  SciPost Phys. 15, 159 (2023) · published 13 October 2023 | Toggle abstract · pdf

  We consider area-preserving deformations of the plane, acting on electronic wave functions through "quantomorphisms" that change both the underlying metric and the confining potential. We show that adiabatic sequences of such transformations produce Berry phases that can be written in closed form in terms of the many-body current and density, even in the presence of interactions. For a large class of deformations that generalize squeezing and shearing, the leading piece of the phase is a super-extensive Aharonov-Bohm term ($\propto N^2$ for $N$ electrons) in the thermodynamic limit. Its gauge-invariant subleading partner only measures the current, whose dominant contribution to the phase stems from a jump at the edge in the limit of strong magnetic fields. This results in a finite Berry curvature per unit area, reminiscent of the Hall viscosity. We show that the latter is in fact included in our formalism, bypassing its standard derivation on a torus and suggesting realistic experimental setups for its observation in quantum simulators.

  2 citations

• Dualities and loops on squashed $S^3$

  Charles Thull

  SciPost Phys. 15, 156 (2023) · published 12 October 2023 | Toggle abstract · pdf

  We consider $\mathcal{N}=4$ supersymmetric gauge theories on the squashed three-sphere with six preserved supercharges. We first discuss how Wilson and vortex loops preserve up to four of the supercharges and we find squashing independence for the expectation values of these 2/3-BPS loops. We then show how the additional supersymmetries facilitate the analytic matching of partition functions and loop operator expectation values to those in the mirror dual theory, allowing one to lift all the results that were previously established on the round sphere to the squashed sphere. Additionally, on the squashed sphere with four preserved supercharges, we numerically evaluate the partition functions of ABJM and its dual super-Yang-Mills at low ranks of the gauge group. We find matching values of their partition functions, prompting us to conjecture the general equality on the squashed sphere. From the numerics we also observe the squashing dependence of the Lee-Yang zeros and of the non-perturbative corrections to the all order large $N$ expression for the ABJM partition function.

  2 citations

• Structural and magnetic anisotropy in YBa$_2$Cu$_3$O$_7$/La$_{0.67}$Sr$_{0.33}$MnO$_3$ bilayer on SrTiO$_3$ substrate

  Ankita Singh, Ram Prakash Pandeya, Sawani Dutta, Srinivas C. Kandukuri, Kalobaran Maiti

  SciPost Phys. Proc. 11, 007 (2023) · published 5 June 2023 | Toggle abstract · pdf

  We study the magnetic properties and emergence of superconductivity in YBa$_2$Cu$_3$O$_7$ (YBCO)/ La$_{0.67}$Sr$_{0.33}$MnO$_3$ (LSMO) heterostructures. Bilayer films of superconducting layer, YBCO, and ferromagnetic layer, LSMO were grown on SrTiO$_{3}$ (STO) (001) substrate using ultrahigh vacuum Pulsed Laser Deposition system. Magnetization data at 100 K as a function of applied magnetic field shows ferromagnetic behaviour due to the LSMO layer. Cooling below 100 K leads to superconductivity in this material; the onset of superconductivity occurs at a temperature, $T_{c,SC},$ of 86 K for $H_{ext}\perp c$ (in-plane) \& 84 K for $H_{ext}||c$ (out-of-plane) under 100 Oe applied field. In-plane magnetic measurements show significant suppression of diamagnetic behaviour as compared to the out-of-plane measurements. The susceptibility signals are higher for out-of-plane direction. Such strong anisotropy in magnetism and the transition temperatures reveal complex interplay of magnetism and superconductivity in this system and calls for further study in this direction.

  2 citations

• Constructing non-Abelian quantum spin liquids using combinatorial gauge symmetry

  Dmitry Green, Claudio Chamon

  SciPost Phys. 15, 067 (2023) · published 22 August 2023 | Toggle abstract · pdf

  We construct Hamiltonians with only 1- and 2-body interactions that exhibit an exact non-Abelian gauge symmetry (specifically, combinatiorial gauge symmetry). Our spin Hamiltonian realizes the quantum double associated to the group of quaternions. It contains only ferromagnetic and anti-ferromagnetic $ZZ$ interactions, plus longitudinal and transverse fields, and therefore is an explicit example of a spin Hamiltonian with no sign problem that realizes a non-Abelian topological phase. In addition to the spin model, we propose a superconducting quantum circuit version with the same symmetry.

  2 citations

• Introducing the Journal of Robustness Reports

  František Bartoš, Alexandra Sarafoglou, Balazs Aczel, Suzanne Hoogeveen, Christopher D. Chambers, Eric-Jan Wagenmakers

  J. Robust. Rep. 0-Editorial (2025) · published 16 April 2025 | Toggle abstract · pdf

  The vast majority of empirical research articles report a single primary analysis outcome that is the result of a single analysis plan, executed by a single analysis team (usually the team that also designed the experiment and collected the data). However, recent many-analyst projects have demonstrated that different analysis teams generally adopt a unique approach and that there exists considerable variability in the associated conclusions. There appears to be no single optimal statistical analysis plan, and different plausible plans need not lead to the same conclusion. A high variability in outcomes signals that the conclusions are relatively fragile and dependent on the specifics of the analysis plan. Crucially, without multiple teams analyzing the data, it is difficult to gauge the extent to which the conclusions are robust. We have recently proposed that empirical articles of particular scientific interest or societal importance are accompanied by two or three short reports that summarize the results of alternative analyses conducted by independent experts [F. Bartoš et al., Nat. Hum. Behav. (2025)]. In order to showcase the practical feasibility and epistemic benefits of this approach we have founded the Journal of Robustness Reports, which is dedicated to publishing short reanalyses of empirical findings. This editorial describes the scope and the workflow of the Journal of Robustness Reports including the type and format of the published articles. We hope that the Journal of Robustness Reports will help make reanalyses of published findings the norm across the empirical sciences.

  2 citations

• Interface junctions in QCD${}_4$

  Pranay Gorantla, Ho Tat Lam

  SciPost Phys. 10, 085 (2021) · published 22 April 2021 | Toggle abstract · pdf

  We study 3+1 dimensional $SU(N)$ Quantum Chromodynamics (QCD) with $N_f$ degenerate quarks that have a spatially varying complex mass. It leads to a network of interfaces connected by interface junctions. We use anomaly inflow to constrain these defects. Based on the chiral Lagrangian and the conjectures on the interfaces, characterized by a spatially varying $\theta$-parameter, we propose a low-energy description of such networks of interfaces. Interestingly, we observe that the operators in the effective field theories on the junctions can carry baryon charges, and their spin and isospin representations coincide with baryons. We also study defects, characterized by spatially varying coupling constants, in 2+1 dimensional Chern-Simons-matter theories and in a 3+1 dimensional real scalar theory.

  2 citations

• Fidelity decay and error accumulation in random quantum circuits

  Nadir Samos Sáenz de Buruaga, Rafał Bistroń, Marcin Rudziński, Rodrigo M. C. Pereira, Karol Życzkowski, Pedro Ribeiro

  SciPost Phys. 19, 013 (2025) · published 8 July 2025 | Toggle abstract · pdf

  Fidelity decay captures the inevitable state degradation in any practical implementation of a quantum process. We devise bounds for the decay of fidelity for a generic evolution given by a random quantum circuit model that encompasses errors arising from the implementation of two-qubit gates and qubit permutations. We show that fidelity decays exponentially with both circuit depth and the number of qubits raised to an architecture-dependent power and we determine the decay rates as a function of the amplitude of the aforementioned errors. Furthermore, we demonstrate the utility of our results in benchmarking quantum processors using the quantum volume figure of merit and provide insights into strategies for improving processor performance. These findings pave the way for understanding how states evolving under generic quantum dynamics degrade due to the accumulation of different kinds of perturbations.

  2 citations