Publications

Order by: publication date number of citations

• On 2d CFTs that interpolate between minimal models

  Sylvain Ribault

  SciPost Phys. 6, 075 (2019) · published 25 June 2019 | Toggle abstract · pdf

  We investigate exactly solvable two-dimensional conformal field theories that exist at generic values of the central charge, and that interpolate between A-series or D-series minimal models. When the central charge becomes rational, correlation functions of these CFTs may tend to correlation functions of minimal models, or diverge, or have finite limits which can be logarithmic. These results are based on analytic relations between four-point structure constants and residues of conformal blocks.

  9 citations

• CrystalNets.jl: Identification of Crystal Topologies

  Lionel Zoubritzky, François-Xavier Coudert

  SciPost Chem. 1, 005 (2022) · published 17 June 2022 | Toggle abstract · pdf

  We present here an open-source Julia library for the topological identification of crystalline materials, with algorithmic and computational improvements over the previously available software in the field, resulting in a speed increase of one order of magnitude. This new algorithm and implementation can therefore be used at large scale in high-throughput screening methodologies. We have validated and benchmarked CrystalNets.jl against a diverse set of crystal databases, covering in particular metal–organic frameworks, aluminophosphates, zeolites, and other inorganic compounds.

  9 citations

• Two invertible networks for the matrix element method

  Anja Butter, Theo Heimel, Till Martini, Sascha Peitzsch, Tilman Plehn

  SciPost Phys. 15, 094 (2023) · published 14 September 2023 | Toggle abstract · pdf

  The matrix element method is widely considered the ultimate LHC inference tool for small event numbers. We show how a combination of two conditional generative neural networks encodes the QCD radiation and detector effects without any simplifying assumptions, while keeping the computation of likelihoods for individual events numerically efficient. We illustrate our approach for the CP-violating phase of the top Yukawa coupling in associated Higgs and single-top production. Currently, the limiting factor for the precision of our approach is jet combinatorics.

  9 citations

• Flow equations for disordered Floquet systems

  Steven J. Thomson, Duarte Magano, Marco Schirò

  SciPost Phys. 11, 028 (2021) · published 10 August 2021 | Toggle abstract · pdf

  In this work, we present a new approach to disordered, periodically driven (Floquet) quantum many-body systems based on flow equations. Specifically, we introduce a continuous unitary flow of Floquet operators in an extended Hilbert space, whose fixed point is both diagonal and time-independent, allowing us to directly obtain the Floquet modes. We first apply this method to a periodically driven Anderson insulator, for which it is exact, and then extend it to driven many-body localized systems within a truncated flow equation ansatz. In particular we compute the emergent Floquet local integrals of motion that characterise a periodically driven many-body localized phase. We demonstrate that the method remains well-controlled in the weakly-interacting regime, and allows us to access larger system sizes than accessible by numerically exact methods, paving the way for studies of two-dimensional driven many-body systems.

  9 citations

• Dynamics of a colloidal particle coupled to a Gaussian field: from a confinement-dependent to a non-linear memory

  Urna Basu, Vincent Démery, Andrea Gambassi

  SciPost Phys. 13, 078 (2022) · published 3 October 2022 | Toggle abstract · pdf

  The effective dynamics of a colloidal particle immersed in a complex medium is often described in terms of an overdamped linear Langevin equation for its velocity with a memory kernel which determines the effective (time-dependent) friction and the correlations of fluctuations. Recently, it has been shown in experiments and numerical simulations that this memory may depend on the possible optical confinement the particle is subject to, suggesting that this description does not capture faithfully the actual dynamics of the colloid, even at equilibrium. Here, we propose a different approach in which we model the medium as a Gaussian field linearly coupled to the colloid. The resulting effective evolution equation of the colloidal particle features a non-linear memory term which extends previous models and which explains qualitatively the experimental and numerical evidence in the presence of confinement. This non-linear term is related to the correlations of the effective noise via a novel fluctuation-dissipation relation which we derive.

  9 citations

• Minimal lectures on two-dimensional conformal field theory

  Sylvain Ribault

  SciPost Phys. Lect. Notes 1 (2018) · published 10 June 2018 | Toggle abstract · pdf

  We provide a brief but self-contained review of conformal field theory on the Riemann sphere. We first introduce general axioms such as local conformal invariance, and derive Ward identities and BPZ equations. We then define minimal models and Liouville theory by specific axioms on their spectrums and degenerate fields. We solve these theories by computing three- and four-point functions, and discuss their existence and uniqueness.

  9 citations

• Spatial structure of unstable normal modes in a glass-forming liquid

  Masanari Shimada, Daniele Coslovich, Hideyuki Mizuno, Atsushi Ikeda

  SciPost Phys. 10, 001 (2021) · published 4 January 2021 | Toggle abstract · pdf

  The phenomenology of glass-forming liquids is often described in terms of their underlying, high-dimensional potential energy surface. In particular, the statistics of stationary points sampled as a function of temperature provides useful insight into the thermodynamics and dynamics of the system. To make contact with the real space physics, however, analysis of the spatial structure of the normal modes is required. In this work, we numerically study the potential energy surface of a glass-forming ternary mixture. Starting from liquid configurations equilibrated over a broad range of temperatures using a swap Monte Carlo method, we locate the nearby stationary points and investigate the spatial architecture and the energetics of the associated unstable modes. Through this spatially-resolved analysis, originally developed to study local minima, we corroborate recent evidence that the nature of the unstable modes changes from delocalized to localized around the mode-coupling temperature. We find that the displacement amplitudes of the delocalized modes have a slowly decaying far field, whereas the localized modes consist of a core with large displacements and a rapidly decaying far field. The fractal dimension of unstable modes around the mobility edge is equal to 1, consistent with the scaling of the participation ratio. Finally, we find that around and below the mode-coupling temperature the unstable modes are localized around structural defects, characterized by a disordered local structure markedly different from the liquid's locally favored structure. These defects are similar to those associated to quasi-localized vibrations in local minima and are good candidates to predict the emergence of localized excitations at low temperature.

  9 citations

• Delocalization transition in low energy excitation modes of vector spin glasses

  Silvio Franz, Flavio Nicoletti, Giorgio Parisi, Federico Ricci-Tersenghi

  SciPost Phys. 12, 016 (2022) · published 12 January 2022 | Toggle abstract · pdf

  We study the energy minima of the fully-connected $m$-components vector spin glass model at zero temperature in an external magnetic field for $m\ge 3$. The model has a zero temperature transition from a paramagnetic phase at high field to a spin glass phase at low field. We study the eigenvalues and eigenvectors of the Hessian in the minima of the Hamiltonian. The spectrum is gapless both in the paramagnetic and in the spin glass phase, with a pseudo-gap behaving as $\lambda^{m-1}$ in the paramagnetic phase and as $\sqrt{\lambda}$ at criticality and in the spin glass phase. Despite the long-range nature of the model, the eigenstates close to the edge of the spectrum display quasi-localization properties. We show that the paramagnetic to spin glass transition corresponds to delocalization of the edge eigenvectors. We solve the model by the cavity method in the thermodynamic limit. We also perform numerical minimization of the Hamiltonian for $N\le 2048$ and compute the spectral properties, that show very strong corrections to the asymptotic scaling approaching the critical point.

  9 citations

• Interaction effects in a multi-channel Fabry-Pérot interferometer in the Aharonov-Bohm regime

  D. Ferraro, E. Sukhorukov

  SciPost Phys. 3, 014 (2017) · published 17 August 2017 | Toggle abstract · pdf

  We investigate a Fabry-P\'erot interferometer in the integer Hall regime in which only one edge channel is transmitted and n channels are trapped into the interferometer loop. Addressing recent experimental observations, we assume that Coulomb blockade effects are completely suppressed due to screening, while keeping track of a residual strong short range electron-electron interaction between the co-propagating edge channels trapped into the interferometer loop. This kind of interaction can be completely described in the framework of the edge-magnetoplasmon scattering matrix theory allowing us to evaluate the backscattering current and the associated differential conductance as a function of the bias voltage. The remarkable features of these quantities are discussed as a function of the number of trapped channels. The developed formalism reveals very general and provides also a simple way to model the experimentally relevant geometry in which some of the trapped channels are absorbed into an Ohmic contact, leading to energy dissipation.

  9 citations

• Stroboscopic aliasing in long-range interacting quantum systems

  Shane P. Kelly, Eddy Timmermans, Jamir Marino, S.-W. Tsai

  SciPost Phys. Core 4, 021 (2021) · published 10 September 2021 | Toggle abstract · pdf

  We unveil a mechanism for generating oscillations with arbitrary multiplets of the period of a given external drive, in long-range interacting quantum many-particle spin systems. These oscillations break discrete time translation symmetry as in time crystals, but they are understood via two intertwined stroboscopic effects similar to the aliasing resulting from video taping a single fast rotating helicopter blade. The first effect is similar to a single blade appearing as multiple blades due to a frame rate that is in resonance with the frequency of the helicopter blades' rotation; the second is akin to the optical appearance of the helicopter blades moving in reverse direction. Analogously to other dynamically stabilized states in interacting quantum many-body systems, this stroboscopic aliasing is robust to detuning and excursions from a chosen set of driving parameters, and it offers a novel route for engineering dynamical $n$-tuplets in long-range quantum simulators, with potential applications to spin squeezing generation and entangled state preparation.

  9 citations