Publications

Order by: publication date number of citations

• Matrix method and the suppression of Runge's phenomenon

  Shui-Fa Shen, Wei-Liang Qian, Jie Zhang, Yu Pan, Yu-Peng Yan, Cheng-Gang Shao

  SciPost Phys. Core 7, 034 (2024) · published 5 June 2024 | Toggle abstract · pdf

  Higher-degree polynomial interpolations carried out on uniformly distributed nodes are often plagued by overfitting, known as Runge's phenomenon. This work investigates Runge's phenomenon and its suppression in various versions of the matrix method for black hole quasinormal modes. It is shown that an appropriate choice of boundary conditions gives rise to desirable suppression of oscillations associated with the increasing Lebesgue constant. For the case of discontinuous effective potentials, where the application of the above boundary condition is not feasible, the recently proposed scheme with delimited expansion domain also leads to satisfactory results. The onset of Runge's phenomenon and its effective suppression are demonstrated by evaluating the relevant waveforms. Furthermore, we argue that both scenarios are either closely related to or practical imitations of the Chebyshev grid. The implications of the present study are also addressed.

  4 citations

• Efficient on-shell matching

  Mikael Chala, Javier L. Miras, José Santiago, Fuensanta Vilches

  SciPost Phys. 18, 185 (2025) · published 11 June 2025 | Toggle abstract · pdf

  We propose an efficient method to perform on-shell matching calculations in effective field theories. The standard off-shell approach to matching requires the use of a Green's basis that includes redundant and evanescent operators. The reduction of such a basis to a physical one is often highly non-trivial, difficult to automate and error prone. Our proposal is based on a numerical solution of the corresponding on-shell matching equations, which automatically implements in a trivial way the delicate cancellation between the non-local terms in the full theory and those in the effective one. The use of rational on-shell kinematics ensures an exact analytic solution despite the numerical procedure. In this way we only need a physical basis to perform the matching. Our procedure can be used to reduce any Green's basis to an arbitrary physical one, or to translate between physical bases; to renormalize arbitrary effective Lagrangians, directly in terms of a physical basis; and to perform finite matching, including evanescent contributions, as we discuss with explicit examples.

  4 citations

• Gravitational higher-form symmetries and the origin of hidden symmetries in Kaluza-Klein compactifications

  Carmen Gómez-Fayrén, Tomás Ortín, Matteo Zatti

  SciPost Phys. Core 8, 010 (2025) · published 29 January 2025 | Toggle abstract · pdf

  We show that, in presence of isometries and non-trivial topology, the Einstein–Hilbert action is invariant under certain transformations of the metric which are not diffeomorphisms. These transformations are similar to the higher-form symmetries of field theories with $p$-form fields. In the context of toroidal Kaluza–Klein compactifications, we show that these symmetries give rise to some of the "hidden symmetries" (dualities) of the dimensionally-reduced theories.

  4 citations

• A Python GPU-accelerated solver for the Gross-Pitaevskii equation and applications to many-body cavity QED

  Lorenzo Fioroni, Luca Gravina, Justyna Stefaniak, Alexander Baumgärtner, Fabian Finger, Davide Dreon, Tobias Donner

  SciPost Phys. Codebases 38 (2024) · published 6 November 2024 | Toggle abstract · pdf

  TorchGPE is a general-purpose Python package developed for solving the Gross-Pitaevskii equation (GPE). This solver is designed to integrate wave functions across a spectrum of linear and non-linear potentials. A distinctive aspect of TorchGPE is its modular approach, which allows the incorporation of arbitrary self-consistent and time-dependent potentials, e.g., those relevant in many-body cavity QED models. The package employs a symmetric split-step Fourier propagation method, effective in both real and imaginary time. In our work, we demonstrate a significant improvement in computational efficiency by leveraging GPU computing capabilities. With the integration of the latter technology, TorchGPE achieves a substantial speed-up with respect to conventional CPU-based methods, greatly expanding the scope and potential of research in this field.

  4 citations

• Jet substructure observables for jet quenching in quark gluon plasma: A machine learning driven analysis

  Miguel Crispim Romão, José Guilherme Milhano, Marco van Leeuwen

  SciPost Phys. 16, 015 (2024) · published 18 January 2024 | Toggle abstract · pdf

  We present a survey of a comprehensive set of jet substructure observables commonly used to study the modifications of jets resulting from interactions with the Quark Gluon Plasma in Heavy Ion Collisions. The JEWEL event generator is used to produce simulated samples of quenched and unquenched jets. Three distinct analyses using Machine Learning techniques on the jet substructure observables have been performed to identify both linear and non-linear relations between the observables, and to distinguish the Quenched and Unquenched jet samples. We find that most of the observables are highly correlated, and that their information content can be captured by a small set of observables. We also find that the correlations between observables are resilient to quenching effects and that specific pairs of observables exhaust the full sensitivity to quenching effects. The code, the datasets, and instructions on how to reproduce this work are also provided.

  4 citations

• Time-reparametrization invariances, multithermalization and the Parisi scheme

  Jorge Kurchan

  SciPost Phys. Core 6, 001 (2023) · published 17 January 2023 | Toggle abstract · pdf

  The Parisi scheme for equilibrium and the corresponding slow dynamics with multithermalization - same temperature common to all observables, different temperatures only possible at widely separated timescales – imply one another. Consistency requires that two systems brought into infinitesimal coupling be able to rearrange their timescales in order that all their temperatures match: this time reorganisation is only possible because the systems have a set of time-reparametrization invariances, that are thus seen to be an essential component of the scenario.

  4 citations

• Random matrix universality in dynamical correlation functions at late times

  Oscar Bouverot-Dupuis, Silvia Pappalardi, Jorge Kurchan, Anatoli Polkovnikov, Laura Foini

  SciPost Phys. 19, 050 (2025) · published 20 August 2025 | Toggle abstract · pdf

  We study the behaviour of two-time correlation functions at late times for finite system sizes considering observables whose (one-point) average value does not depend on energy. In the long time limit, we show that such correlation functions display a ramp and a plateau determined by the correlations of energy levels, similar to what is already known for the spectral form factor. The plateau value is determined, in absence of degenerate energy levels, by the fluctuations of diagonal matrix elements, which highlights differences between different symmetry classes. We show this behaviour analytically by employing results from Random Matrix Theory and the Eigenstate Thermalisation Hypothesis, and numerically by exact diagonalization in the toy example of a Hamiltonian drawn from a Random Matrix ensemble and in a more realistic example of disordered spin glasses at high temperature. Importantly, correlation functions in the ramp regime do not show self-averaging behaviour, and, at difference with the spectral form factor the time average does not coincide with the ensemble average.

  4 citations

• The DarkSide-20k TPC and underground argon cryogenic system

  Thomas N. Thorpe on behalf of the DS-20k collaboration

  SciPost Phys. Proc. 12, 069 (2023) · published 5 July 2023 | Toggle abstract · pdf

  DarkSide-20k (DS-20k) will exploit the physical and chemical properties of liquid argon (LAr) housed within a large dual-phase time project chamber (TPC) in its direct search for dark matter. The TPC will utilize a compact, integrated design with many novel features to enable the 20t fiducial volume of underground argon. Underground Argon (UAr) is sourced from underground CO$_2$ wells and depleted in the radioactive isotope $^{39}$Ar, greatly enhancing the experimental sensitivity to dark matter interactions. Sourcing and transporting the $\mathcal{O}$(100t) of UAr for (DS-20k) is costly, and a dedicated single-closed-loop cryogenic system has been designed, constructed, and tested to handle the valuable UAr. We present an overview of the (DS-20k) TPC design and the first results from the UAr cryogenic system.

  4 citations

• High-low pressure domain wall for the classical Toda lattice

  Christian B. Mendl, Herbert Spohn

  SciPost Phys. Core 5, 002 (2022) · published 24 January 2022 | Toggle abstract · pdf

  We study the classical Toda lattice with domain wall initial conditions, for which left and right half lattice are in thermal equilibrium but with distinct parameters of pressure, mean velocity, and temperature. In the hydrodynamic regime the respective space-time profiles scale ballisticly. The particular case of interest is a jump from low to high pressure at uniform temperature and zero mean velocity. Thereby the scaling function for the average stretch (also free volume) is forced to change sign. By direct inspection, the hydrodynamic equations for the Toda lattice seem to be singular at zero stretch. In our contribution we report on numerical solutions and convincingly establish that nevertheless the self-similar solution exhibits smooth behavior.

  4 citations

• Proliferation of non-linear excitations in the piecewise-linear perceptron

  Antonio Sclocchi, Pierfrancesco Urbani

  SciPost Phys. 10, 013 (2021) · published 21 January 2021 | Toggle abstract · pdf

  We investigate the properties of local minima of the energy landscape of a continuous non-convex optimization problem, the spherical perceptron with piecewise linear cost function and show that they are critical, marginally stable and displaying a set of pseudogaps, singularities and non-linear excitations whose properties appear to be in the same universality class of jammed packings of hard spheres. The piecewise linear perceptron problem appears as an evolution of the purely linear perceptron optimization problem that has been recently investigated in [1]. Its cost function contains two non-analytic points where the derivative has a jump. Correspondingly, in the non-convex/glassy phase, these two points give rise to four pseudogaps in the force distribution and this induces four power laws in the gap distribution as well. In addition one can define an extended notion of isostaticity and show that local minima appear again to be isostatic in this phase. We believe that our results generalize naturally to more complex cases with a proliferation of non-linear excitations as the number of non-analytic points in the cost function is increased.

  4 citations