Publications

Order by: publication date number of citations

• Aperiodic spin chains at the boundary of hyperbolic tilings

  Pablo Basteiro, Rathindra Nath Das, Giuseppe Di Giulio, Johanna Erdmenger

  SciPost Phys. 15, 218 (2023) · published 30 November 2023 | Toggle abstract · pdf

  In view of making progress towards establishing a holographic duality for theories defined on a discrete tiling of the hyperbolic plane, we consider a recently proposed boundary spin chain Hamiltonian with aperiodic couplings that are chosen such as to reflect the inflation rule, i.e. the construction principle, of the bulk tiling. As a remnant of conformal symmetry, the spin degrees of freedom are arranged in multiplets of the dihedral group under which the bulk lattice is invariant. For the boundary Hamiltonian, we use strong-disorder RG techniques and evaluate correlation functions, the entanglement entropy and mutual information for the case that the ground state is in an aperiodic singlet phase. We find that two-point functions decay as a power-law with exponent equal to one. Furthermore, we consider the case that the spin variables transform in the fundamental representation of SO(N), leading to a gapless system, and find that the effective central charge obtained from the entanglement entropy scales as lnN, reflecting the number of local degrees of freedom. We also determine the dependence of this central charge on the parameters specifying the bulk tiling. Moreover, we obtain an analytical expression for the mutual information, according to which there is no phase transition at any finite value of the distance between the two intervals involved.

  1 citation

• Codebase release 0.2 for Pychastic

  Radost Waszkiewicz, Maciej Bartczak, Kamil Kolasa, Maciej Lisicki

  SciPost Phys. Codebases 11-r0.2 (2023) · published 3 April 2023 | Toggle abstract · src

  In the last decade, Python-powered physics simulations ecosystem has been growing steadily, allowing greater interoperability, and becoming an important tool in numerical exploration of physical phenomena, particularly in soft matter systems. Driven by the need for fast and precise numerical integration in colloidal dynamics, here we formulate the problem of Brownian Dynamics (BD) in a mathematically consistent formalism of the Itō calculus, and develop a Python package to assist numerical computations. We show that, thanks to the automatic differentiation packages, the classical truncated Taylor-Itō integrators can be implemented without the burden of computing the derivatives of the coefficient functions beforehand. Furthermore, we show how to circumvent the difficulties of BD simulations such as calculations of the divergence of the mobility tensor in the diffusion equation and discontinuous trajectories encountered when working with dynamics on $S^2$ and $SO(3)$. The resulting Python package, Pychastic, is capable of performing BD simulations including hydrodynamic interactions at speeds comparable to dedicated implementations in lower-level programming languages, but with a much simpler end-user interface.

  1 citation

• Photomultiplier characterisation and its impact on background for SABRE South

  William J. D. Melbourne, Owen Stanley, Phillip Urquijo, Madeleine J. Zurowski

  SciPost Phys. Proc. 12, 061 (2023) · published 5 July 2023 | Toggle abstract · pdf

  SABRE (Sodium iodide with Active Background REjection) South is a NaI(Tl) based dark matter direct detection experiment located at the Stawell Underground Physics Laboratory (SUPL) [J. Phys. Conf. Ser. 2156, 012064 (2021), arXiv:2205.13849]. It is designed to detect an annual modulation of WIMP recoils as an independent replication of the long-standing DAMA/LIBRA modulation signal. SABRE South will have a low energy threshold of 1 keV in the NaI(Tl) crystal detector and a low experimental background. This requires precise characterisation of the photomultipliers used to understand both their sensitivity at low thresholds and their contribution to the background. We report on the photomultiplier characterisation test bench developed for the crystal detector photomultipliers including studies of the single photon response, transit time, and dark noise. A specific focus is on estimating the contribution to the experimental background of coincident photomultiplier noise due to its predominance at low energy and inability to be modelled using traditional MC simulation.

  1 citation

• NLO electroweak and QCD corrections to off-shell ttW production at the LHC

  Ansgar Denner, Giovanni Pelliccioli

  SciPost Phys. Proc. 7, 034 (2022) · published 21 June 2022 | Toggle abstract · pdf

  The foreseen luminosities for the next LHC runs will enable precise differential measurements of the associated production of top-antitop pairs with a W boson. Therefore, providing accurate theory predictions for this process is needed for realistic final states. We present the first combination of NLO electroweak and QCD corrections to off-shell ttW$^+$ production in the three-charged-lepton channel, including non-resonant effects, full spin-correlations and interferences. Such radiative corrections comprise the electroweak and QCD corrections to the leading QCD order, and the QCD corrections to the leading electroweak order.

  1 citation

• A path integral ground state Monte Carlo algorithm for entanglement of lattice bosons

  Emanuel Casiano-Diaz, C. M. Herdman, Adrian Del Maestro

  SciPost Phys. 14, 054 (2023) · published 29 March 2023 | Toggle abstract · pdf

  A ground state path integral quantum Monte Carlo algorithm is introduced that allows for the study of entanglement in lattice bosons at zero temperature. The Rényi entanglement entropy between spatial subregions is explored across the phase diagram of the one dimensional Bose-Hubbard model for systems consisting of up to $L=256$ sites at unit-filling without any restrictions on site occupancy, far beyond the reach of exact diagonalization. The favorable scaling of the algorithm is demonstrated through a further measurement of the Rényi entanglement entropy at the two dimensional superfluid-insulator critical point for large system sizes, confirming the existence of the expected entanglement boundary law in the ground state. The Rényi estimator is extended to measure the symmetry resolved entanglement that is operationally accessible as a resource for experimentally relevant lattice gases with fixed total particle number.

  1 citation

• Functional renormalisation group approach to shell models of turbulence

  Côme Fontaine, Malo Tarpin, Freddy Bouchet, Léonie Canet

  SciPost Phys. 15, 212 (2023) · published 28 November 2023 | Toggle abstract · pdf

  Shell models are simplified models of hydrodynamic turbulence, retaining only some essential features of the original equations, such as the non-linearity, symmetries and quadratic invariants. Yet, they were shown to reproduce the most salient properties of developed turbulence, in particular universal statistics and multi-scaling. We set up the functional renormalisation group (FRG) formalism to study generic shell models. In particular, we formulate an inverse RG flow, which consists in integrating out fluctuation modes from the large scales (small wavenumbers) to the small scales (large wavenumbers), which is physically grounded and has long been advocated in the context of turbulence. Focusing on the Sabra shell model, we study the effect of both a large-scale forcing, and a power-law forcing exerted at all scales. We show that these two types of forcing yield different fixed points, and thus correspond to distinct universality classes, characterised by different scaling exponents. We find that the power-law forcing leads to dimensional (K41-like) scaling, while the large-scale forcing entails anomalous scaling.

  1 citation

• Massless Rarita-Schwinger equations: Half and three halves spin solution

  Mauricio Valenzuela, Jorge Zanelli

  SciPost Phys. 16, 065 (2024) · published 4 March 2024 | Toggle abstract · pdf

  Counting the degrees of freedom of the massless Rarita-Schwinger theory is revisited using Behrends-Fronsdal projectors. The identification of the gauge invariant part of the vector-spinor is thus straightforward, consisting of spins 1/2 and 3/2. The validity of this statement is supported by the explicit solution found in the standard gamma-traceless gauge. Since the obtained systems are deterministic -free of arbitrary functions of time- we argue that the often-invoked residual gauge symmetry lacks fundamental grounding and should not be used to enforce new external constraints. The result is verified by the total Hamiltonian dynamics. We conclude that eliminating the spin-1/2 mode via the extended Hamiltonian dynamics would be acceptable if the Dirac conjecture was assumed; however, this framework does not accurately describe the original Lagrangian system.

  1 citation

• UV completion of extradimensional Yang-Mills theory for Gauge-Higgs unification

  Álvaro Pastor-Gutiérrez, Masatoshi Yamada

  SciPost Phys. 15, 101 (2023) · published 19 September 2023 | Toggle abstract · pdf

  The $SU(N)$ Yang-Mills theory in $\mathbb R^4\times S^1$ spacetime is studied as a simple toy model of Gauge-Higgs unification. The theory is perturbatively nonrenormalizable but could be formulated as an asymptotically safe theory, namely a nonperturbatively renormalizable theory. We study the fixed point structure of the Yang-Mills theory in $\mathbb R^4\times S^1$ by using the functional renormalization group in the background field approximation. We derive the functional flow equations for the gauge coupling and the background gauge-field potential. There exists a nontrivial fixed point for both couplings at finite compactification radii. At the fixed point, gauge coupling and vacuum energy are both relevant. The renormalization group flow of the gauge coupling describes the smooth transition between the ultraviolet asymptotically safe regime and the strong interacting infrared limit.

  1 citation

• Cracking hadron and nuclear collisions open with ropes and string shoving in PYTHIA8

  Smita Chakraborty

  SciPost Phys. Proc. 10, 017 (2022) · published 10 August 2022 | Toggle abstract · pdf

  Enhancement in strangeness yields in heavy-ion collisions is regarded as one of the attributes of the Quark-Gluon Plasma (QGP) along with jet quenching and final-state collectivity. To reproduce these effects in the MC implementation of the Lund string model in \pythia, the inclusion of non-perturbative mechanisms like string shoving and rope hadronization is crucial. In this proceeding, we discuss our latest implementation of these mechanisms and the preliminary results for the strangeness enhancement in high-multiplicity p-p, p-Pb and Xe-Xe. We conclude with remarks on the ongoing development of the model.

  1 citation

• 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.

  1 citation