Publications

Order by: publication date number of citations

• Associative bond swaps in molecular dynamics

  Simone Ciarella, Wouter G. Ellenbroek

  SciPost Phys. 12, 128 (2022) · published 12 April 2022 | Toggle abstract · pdf

  We implement a three-body potential to model associative bond swaps, and release it as part of the HOOMD-blue software. The use of a three-body potential to model swaps has been proven to be effective and has recently provided useful insights into the mechanics and dynamics of adaptive network materials such as vitrimers. It is elegant because it can be used in plain molecular dynamics simulations without the need for topology-altering Monte Carlo steps, and naturally represents typical physical features such as slip-bond behavior. It is easily tunable with a single parameter to control the average swap rate. Here, we show how associative bond swaps can be used to speed up the equilibration of systems that self-assemble by avoiding traps and pitfalls, corresponding to long-lived metastable configurations. Our results demonstrate the possibilities of these swaps not only for modeling systems that are associative by nature, but also for increasing simulation efficiency in other systems that are modellable in HOOMD-blue.

  2 citations

• Boundary description of microstates of the two-dimensional black hole

  Amr Ahmadain, Alexander Frenkel, Krishnendu Ray, Ronak M. Soni

  SciPost Phys. 16, 020 (2024) · published 22 January 2024 | Toggle abstract · pdf

  We identify the microstates of the non-supersymmetric, asymptotically flat 2d black hole in the dual c=1 matrix quantum mechanics (MQM). We calculate the partition function of the theory using Hamiltonian methods and reproduce one of two conflicting results found by Kazakov and Tseytlin. We find the entropy by counting states and the energy by approximately solving the Schrödinger equation. The dominant contribution to the partition function in the double-scaling limit is a novel bound state that can be considered an explicit dual of the black hole microstates. This bound state is long-lived and evaporates slowly, exactly like a black hole in asymptotically flat space.

  2 citations

• Gauging tensor networks with belief propagation

  Joseph Tindall, Matt Fishman

  SciPost Phys. 15, 222 (2023) · published 1 December 2023 | Toggle abstract · pdf

  Effectively compressing and optimizing tensor networks requires reliable methods for fixing the latent degrees of freedom of the tensors, known as the gauge. Here we introduce a new algorithm for gauging tensor networks using belief propagation, a method that was originally formulated for performing statistical inference on graphical models and has recently found applications in tensor network algorithms. We show that this method is closely related to known tensor network gauging methods. It has the practical advantage, however, that existing belief propagation implementations can be repurposed for tensor network gauging, and that belief propagation is a very simple algorithm based on just tensor contractions so it can be easier to implement, optimize, and generalize. We present numerical evidence and scaling arguments that this algorithm is faster than existing gauging algorithms, demonstrating its usage on structured, unstructured, and infinite tensor networks. Additionally, we apply this method to improve the accuracy of the widely used simple update gate evolution algorithm.

  2 citations

• SINDRUM II

  A. van der Schaaf

  SciPost Phys. Proc. 5, 008 (2021) · published 6 September 2021 | Toggle abstract · pdf

  In 1987 a collaboration including ETHZ - UZH - PSI - RWTH Aachen - Univ. Tbilisi proposed a new search for μe conversion in muonic atoms. The SINDRUM II spectrometer came into operation in the PSI μE1 area in 1989, but a dedicated beam line was delayed until 1998 by technical setbacks.

  2 citations

• Test lepton flavor universality with (semi)leptonic $D$ decays at BESIII

  S. F. Zhang on behalf of the BESIII Collaboration

  SciPost Phys. Proc. 1, 016 (2019) · published 19 February 2019 | Toggle abstract · pdf

  Using 2.93~fb$^{-1}$ data taken at $\sqrt{s}=3.773$~GeV, 0.482~fb$^{-1}$ data taken at $\sqrt{s}=4.009$~GeV and 3.19~fb$^{-1}$ data taken at $\sqrt{s}=4.178$~GeV with the BESIII detector, precision measurements of the branching fractions of $D^0\to K^-\mu^+\nu_\mu$, $D^+\to\bar K^0\mu^+\nu_\mu$, $D^0\to\pi^-\mu^+\nu_\mu$, $D^+\to\pi^0\mu^+\nu_\mu$, $D^+\to\ell^+\nu_\ell$ and $D_s^+\to\ell^+\nu_\ell$ are performed. Combining the known branching fractions of $D\to\bar Ke^+\nu_e$, $D\to\pi e^+\nu_e$ and $D^+_s\to\tau^+\nu_\tau$, we have tested the lepton flavor universality with $D\to\bar K\ell^+\nu_\ell$, $D\to\pi\ell^+\nu_\ell$, $D^+\to\ell^+\nu_\ell$ and $D_{s}^+\to\ell^+\nu_\ell$ decays. We have also tested lepton flavor universality in different $q_{\ell\nu_\ell}^2$ intervals for $D\to\bar K\ell^+\nu_\ell$~($\ell=e$ or $\mu$). Besides, hadronic form factor $f_+^K(0)$, $D$ meson decay constant $f_{D_s^+}$ and $f_{D^+}$, and quark mixing matrix element $|V_{cs}|$ and $|V_{cd}|$ are also extracted with the most precise accuracies to date.

  2 citations

• Structural classification of boron nitride twisted bilayers and ab initio investigation of their stacking-dependent electronic structure

  Sylvain Latil, Hakim Amara, Lorenzo Sponza

  SciPost Phys. 14, 053 (2023) · published 29 March 2023 | Toggle abstract · pdf

  Since the discovery of superconductive twisted bilayer graphene which initiated the field of twistronics, moiré systems have not ceased to exhibit fascinating properties. We demonstrate that in boron nitride twisted bilayers, for a given moiré periodicity, there are five different stackings which preserve the monolayer hexagonal symmetry (i.e. the invariance upon rotations of 120°) and not only two as always discussed in literature. We introduce some definitions and a nomenclature that identify unambiguously the twist angle and the stacking sequence of any hexagonal bilayer with order-3 rotation symmetry. Moreover, we employ density functional theory to study the evolution of the band structure as a function of the twist angle for each of the five stacking sequences of boron nitride bilayers. We show that the gap is indirect at any angle and in any stacking, and identify features that are conserved within the same stacking sequence irrespective of the angle of twist.

  2 citations

• Integrable deformations of superintegrable quantum circuits

  Tamás Gombor, Balázs Pozsgay

  SciPost Phys. 16, 114 (2024) · published 26 April 2024 | Toggle abstract · pdf

  Superintegrable models are very special dynamical systems: they possess more conservation laws than what is necessary for integrability. This severely constrains their dynamical processes, and it often leads to their exact solvability, even in non-equilibrium situations. In this paper we consider special Hamiltonian deformations of superintegrable quantum circuits. The deformations break superintegrability, but they preserve integrability. We focus on a selection of concrete models and show that for each model there is an (at least) one parameter family of integrable deformations. Our most interesting example is the so-called Rule54 model. We show that the model is compatible with a one parameter family of Yang-Baxter integrable spin chains with six-site interaction. Therefore, the Rule54 model does not have a unique integrability structure, instead it lies at the intersection of a family of quantum integrable models.

  2 citations

• Relating non-Hermitian and Hermitian quantum systems at criticality

  Chang-Tse Hsieh, Po-Yao Chang

  SciPost Phys. Core 6, 062 (2023) · published 12 September 2023 | Toggle abstract · pdf

  We demonstrate three types of transformations that establish connections between Hermitian and non-Hermitian quantum systems at criticality, which can be described by conformal field theories (CFTs). For the transformation preserving both the energy and the entanglement spectra, the corresponding central charges obtained from the logarithmic scaling of the entanglement entropy are identical for both Hermitian and non-Hermitian systems. The second transformation, while preserving the energy spectrum, does not perserve the entanglement spectrum. This leads to different entanglement entropy scalings and results in different central charges for the two types of systems. We demonstrate this transformation using the dilation method applied to the free fermion case. Through this method, we show that a non-Hermitian system with central charge $c = -4$ can be mapped to a Hermitian system with central charge $c = 2$. Lastly, we investigate the Galois conjugation in the Fibonacci model with the parameter $\phi \to - 1/\phi$, in which the transformation does not preserve both energy and entanglement spectra. We demonstrate the Fibonacci model and its Galois conjugation relate the tricritical Ising model/3-state Potts model and the Lee-Yang model with negative central charges from the scaling property of the entanglement entropy.

  2 citations

• Unveiling the anatomy of mode-coupling theory

  Ilian Pihlajamaa, Vincent E. Debets, Corentin C. L. Laudicina, Liesbeth M. C. Janssen

  SciPost Phys. 15, 217 (2023) · published 29 November 2023 | Toggle abstract · pdf

  The mode-coupling theory of the glass transition (MCT) has been at the forefront of fundamental glass research for decades, yet the theory's underlying approximations remain obscure. Here we quantify and critically assess the effect of each MCT approximation separately. Using Brownian dynamics simulations, we compute the memory kernel predicted by MCT after each approximation in its derivation, and compare it with the exact one. We find that some often-criticized approximations are in fact very accurate, while the opposite is true for others, providing new guiding cues for further theory development.

  2 citations

• LHC tau-pair production constraints on $a_\tau$ and $d_\tau$

  Ulrich Haisch, Luc Schnell, Joachim Weiss

  SciPost Phys. 16, 048 (2024) · published 14 February 2024 | Toggle abstract · pdf

  We point out that relevant constraints on the anomalous magnetic ($a_\tau$) and electric ($d_\tau$) moment of the tau lepton can be derived from tau-pair production measurements performed at the LHC. Our conclusion is based on the observation that the leading relative deviations from the Standard Model prediction for $pp \to \tau^+ \tau^-$ due to $a_\tau$ and $d_\tau$ are enhanced at high energies. Less precise measurements at hadron colliders can therefore offer the same or better sensitivity to new physics with respect to high-precision low-energy measurements performed at lepton machines. We derive bounds on $a_\tau$ and $d_\tau$ using the full LHC Run II data set on tau-pair production and compare our findings with the current best limits on the tau anomalous moments.

  2 citations