Publications

Order by: publication date number of citations

• A non-abelian analogue of DBI from $T \overline{T}$

  T. Daniel Brennan, Christian Ferko, Savdeep Sethi

  SciPost Phys. 8, 052 (2020) · published 7 April 2020 | Toggle abstract · pdf

  The Dirac action describes the physics of the Nambu-Goldstone scalars found on branes. The Born-Infeld action defines a non-linear theory of electrodynamics. The combined Dirac-Born-Infeld (DBI) action describes the leading interactions supported on a single D-brane in string theory. We define a non-abelian analogue of DBI using the $T \overline{T}$ deformation in two dimensions. The resulting quantum theory is compatible with maximal supersymmetry and such theories are quite rare.

  23 citations

• On-shell effective theory for higher-spin dark matter

  Adam Falkowski, Giulia Isabella, Camila S. Machado

  SciPost Phys. 10, 101 (2021) · published 6 May 2021 | Toggle abstract · pdf

  We apply the on-shell amplitude techniques in the domain of dark matter. Without evoking fields and Lagrangians, an effective theory for a massive spin-$S$ particle is defined in terms of on-shell amplitudes, which are written down using the massive spinor formalism. This procedure greatly simplifies the study of theories with a higher-spin dark matter particle. In particular, it provides an efficient way to calculate the rates of processes controlling dark matter production, and offers better physical insight into how different processes depend on the relevant scales in the theory. We demonstrate the applicability of these methods by exploring two scenarios where higher-spin DM is produced via the freeze-in mechanism. One scenario is minimal, involving only universal gravitational interactions, and is compatible with dark matter masses in a very broad range from sub-TeV to the GUT scale. The other scenario involves direct coupling of higher-spin DM to the Standard Model via the Higgs intermediary, and leads to a rich phenomenology, including dark matter decay signatures.

  23 citations

• Unruh effect for interacting particles with ultracold atoms

  Arkadiusz Kosior, Maciej Lewenstein, Alessio Celi

  SciPost Phys. 5, 061 (2018) · published 11 December 2018 | Toggle abstract · pdf

  The Unruh effect is a quantum relativistic effect where the accelerated observer perceives the vacuum as a thermal state. Here we propose the experimental realization of the Unruh effect for interacting ultracold fermions in optical lattices by a sudden quench resulting in vacuum acceleration with varying interactions strengths in the real temperature background. We observe the inversion of statistics for the low lying excitations in the Wightman function as a result of competition between the spacetime and BCS Bogoliubov transformations. This paper opens up new perspectives for simulators of quantum gravity.

  23 citations

• The High Intensity Proton Accelerator Facility

  J. Grillenberger, C. Baumgarten, M. Seidel

  SciPost Phys. Proc. 5, 002 (2021) · published 6 September 2021 | Toggle abstract · pdf

  The High Intensity Proton Accelerator Facility at PSI routinely provides a proton beam with up to $1.4\,\rm{MW}$ power at a kinetic energy of $590\,\rm{MeV}$. The beam is used to generate neutrons in spallation targets and pions in meson production targets. The pions decay into muons and neutrinos, with applications focused on condensed matter research and particle physics at the intensity frontier. This section presents the main physics and technology concepts utilized in the facility. It includes beam dynamics, the control of beam losses and activation, power conversion, efficiency aspects, and performance figures, e.g., the availability of the facility.

  23 citations

• Reports of my demise are greatly exaggerated: $N$-subjettiness taggers take on jet images

  Liam Moore, Karl Nordström, Sreedevi Varma, Malcolm Fairbairn

  SciPost Phys. 7, 036 (2019) · published 24 September 2019 | Toggle abstract · pdf

  We compare the performance of a convolutional neural network (CNN) trained on jet images with dense neural networks (DNNs) trained on n-subjettiness variables to study the distinguishing power of these two separate techniques applied to top quark decays. We find that they perform almost identically and are highly correlated once jet mass information is included, which suggests they are accessing the same underlying information which can be intuitively understood as being contained in 4-, 5-, 6-, and 8-body kinematic phase spaces depending on the sample. This suggests both of these methods are highly useful for heavy object tagging and provides a tentative answer to the question of what the image network is actually learning.

  23 citations

• Random matrix theory of the isospectral twirling

  Salvatore F. E. Oliviero, Lorenzo Leone, Francesco Caravelli, Alioscia Hamma

  SciPost Phys. 10, 076 (2021) · published 25 March 2021 | Toggle abstract · pdf

  We present a systematic construction of probes into the dynamics of isospectral ensembles of Hamiltonians by the notion of Isospectral twirling, expanding the scopes and methods of ref.[1]. The relevant ensembles of Hamiltonians are those defined by salient spectral probability distributions. The Gaussian Unitary Ensembles (GUE) describes a class of quantum chaotic Hamiltonians, while spectra corresponding to the Poisson and Gaussian Diagonal Ensemble (GDE) describe non chaotic, integrable dynamics. We compute the Isospectral twirling of several classes of important quantities in the analysis of quantum many-body systems: Frame potentials, Loschmidt Echos, OTOCs, Entanglement, Tripartite mutual information, coherence, distance to equilibrium states, work in quantum batteries and extension to CP-maps. Moreover, we perform averages in these ensembles by random matrix theory and show how these quantities clearly separate chaotic quantum dynamics from non chaotic ones.

  23 citations

• Many-body quantum dynamics slows down at low density

  Xiao Chen, Yingfei Gu, Andrew Lucas

  SciPost Phys. 9, 071 (2020) · published 12 November 2020 | Toggle abstract · pdf

  We study quantum many-body systems with a global U(1) conservation law, focusing on a theory of $N$ interacting fermions with charge conservation, or $N$ interacting spins with one conserved component of total spin. We define an effective operator size at finite chemical potential through suitably regularized out-of-time-ordered correlation functions. The growth rate of this density-dependent operator size vanishes algebraically with charge density; hence we obtain new bounds on Lyapunov exponents and butterfly velocities in charged systems at a given density, which are parametrically stronger than any Lieb-Robinson bound. We argue that the density dependence of our bound on the Lyapunov exponent is saturated in the charged Sachdev-Ye-Kitaev model. We also study random automaton quantum circuits and Brownian Sachdev-Ye-Kitaev models, each of which exhibit a different density dependence for the Lyapunov exponent, and explain the discrepancy. We propose that our results are a cartoon for understanding Planckian-limited energy-conserving dynamics at finite temperature.

  23 citations

• Eikonal amplitudes from curved backgrounds

  Tim Adamo, Andrea Cristofoli, Piotr Tourkine

  SciPost Phys. 13, 032 (2022) · published 25 August 2022 | Toggle abstract · pdf

  Eikonal exponentiation in QFT describes the emergence of classical physics at long distances in terms of a non-trivial resummation of infinitely many diagrams. Long ago, 't Hooft proposed a beautiful correspondence between ultra-relativistic scalar eikonal scattering and one-to-one scattering in a background shockwave space-time, bypassing the need to resum. In this spirit, we propose here a covariant method for computing one-to-one amplitudes in curved background space-times which gives rise what we conjecture to be a general expression for the eikonal amplitude. We show how the one-to-one scattering amplitude for scalars on any stationary space-time reduces to a boundary term that captures the long-distance behavior of the background and has the structure of an exponentiated eikonal amplitude. In the case of scalar scattering on Schwarzschild, we recover the known results for gravitational scattering of massive scalars in the eikonal regime. For Kerr, we find a remarkable exponentiation of the tree-level amplitude for gravitational scattering between a massive scalar and a massive particle of infinite spin. This amplitude exhibits a Kawai-Lewellen-Tye-like factorization, which we use to evaluate the eikonal amplitude in momentum space, and study its analytic properties.

  23 citations

• Liu-Nagel phase diagrams in infinite dimension

  Giulio Biroli, Pierfrancesco Urbani

  SciPost Phys. 4, 020 (2018) · published 27 April 2018 | Toggle abstract · pdf

  We study Harmonic Soft Spheres as a model of thermal structural glasses in the limit of infinite dimensions. We show that cooling, compressing and shearing a glass lead to a Gardner transition and, hence, to a marginally stable amorphous solid as found for Hard Spheres systems. A general outcome of our results is that a reduced stability of the glass favors the appearance of the Gardner transition. Therefore using strong perturbations, e.g. shear and compression, on standard glasses or using weak perturbations on weakly stable glasses, e.g. the ones prepared close to the jamming point, are the generic ways to induce a Gardner transition. The formalism that we discuss allows to study general perturbations, including strain deformations that are important to study soft glassy rheology at the mean field level.

  23 citations

• Fast counting with tensor networks

  Stefanos Kourtis, Claudio Chamon, Eduardo R. Mucciolo, Andrei E. Ruckenstein

  SciPost Phys. 7, 060 (2019) · published 12 November 2019 | Toggle abstract · pdf

  We introduce tensor network contraction algorithms for counting satisfying assignments of constraint satisfaction problems (#CSPs). We represent each arbitrary #CSP formula as a tensor network, whose full contraction yields the number of satisfying assignments of that formula, and use graph theoretical methods to determine favorable orders of contraction. We employ our heuristics for the solution of #P-hard counting boolean satisfiability (#SAT) problems, namely monotone #1-in-3SAT and #Cubic-Vertex-Cover, and find that they outperform state-of-the-art solvers by a significant margin.

  23 citations