Publications

Order by: publication date number of citations

• The giant graviton expansion in $AdS_5 \times S^5$

  Giorgos Eleftheriou, Sameer Murthy, Martí Rosselló

  SciPost Phys. 17, 098 (2024) · published 1 October 2024 | Toggle abstract · pdf

  The superconformal index of $\frac12$-BPS states of $\mathcal{N}=4$ $U(N)$ super Yang-Mills theory has a known infinite $q$-series expression with successive terms suppressed by $q^N$. We derive a holographic bulk interpretation of this series by evaluating the corresponding functional integral in the dual AdS$_5 × S^5$. The integral localizes to a product of small fluctuations of the vacuum and of the collective modes of an arbitrary number of giant-gravitons wrapping an $S^3$ of maximal size inside the $S^5$. The quantum mechanics of the small fluctuations of one maximal giant is described by a supersymmetric version of the Landau problem. The quadratic fluctuation determinant reduces to a sum over the supersymmetric ground states, and precisely reproduces the first non-trivial term in the infinite series. Further, we show that the terms corresponding to multiple giants are obtained precisely by the matrix versions of the above super-quantum-mechanics.

• Bethe vectors and recurrence relations for twisted Yangian based models

  Vidas Regelskis

  SciPost Phys. 17, 126 (2024) · published 5 November 2024 | Toggle abstract · pdf

  We study Olshanski twisted Yangian based models, known as one-dimensional "soliton non-preserving" open spin chains, by means of algebraic Bethe Ansatz. The even case, when the bulk symmetry is $\mathfrak{gl}_{2n}$ and the boundary symmetry is $\mathfrak{sp}_{2n}$ or $\mathfrak{so}_{2n}$, was studied in [Ann. Henri Poincaré 20, 339 (2018)]. In the present work, we focus on the odd case, when the bulk symmetry is $\mathfrak{gl}_{2n+1}$ and the boundary symmetry is $\mathfrak{so}_{2n+1}$. We explicitly construct Bethe vectors and present a more symmetric form of the trace formula. We use the composite model approach and $Y(\mathfrak{gl}_n)$-type recurrence relations to obtain recurrence relations for twisted Yangian based Bethe vectors, for both even and odd cases.

• Nonequilibrium probability currents in optically-driven colloidal suspensions

  Samudrajit Thapa, Daniel Zaretzky, Ron Vatash, Grzegorz Gradziuk, Chase Broedersz, Yair Shokef, Yael Roichman

  SciPost Phys. 17, 096 (2024) · published 1 October 2024 | Toggle abstract · pdf

  In the absence of directional motion it is often hard to recognize athermal fluctuations. Probability currents provide such a measure in terms of the rate at which they enclose area in the reduced phase space. We measure this area enclosing rate for trapped colloidal particles, where only one particle is driven. By combining experiment, theory, and simulation, we single out the effect of the different time scales in the system on the measured probability currents. In this controlled experimental setup, particles interact hydrodynamically. These interactions lead to a strong spatial dependence of the probability currents and to a local influence of athermal agitation. In a multiple-particle system, we show that even when the driving acts only on one particle, probability currents occur between other, non-driven particles. This may have significant implications for the interpretation of fluctuations in biological systems containing elastic networks in addition to a suspending fluid.

• Generating the electro-weak scale by vector-like quark condensation

  Sophie Klett, Manfred Lindner, Andreas Trautner

  SciPost Phys. 14, 076 (2023) · published 19 April 2023 | Toggle abstract · pdf

  We show that vector-like quarks in the fundamental or higher-dimensional representations of QCD can generate the electro-weak scale in a phenomenologically viable way by chiral symmetry breaking condensates. The thereby generated scales are determined by numerically solving the Dyson-Schwinger equation and these scales are sizable, because they grow with the hard vector-like mass. Communicating such a scale to the Standard Model via a conformally invariant scalar sector can dynamically generate the electro-weak scale without a naturalness problem, because all non-dynamical mass scales are protected by chiral symmetry. We present a minimal setup which requires only a new neutral scalar with mass not too far above the electro-weak scale, as well as vector-like quarks at the (multi-)TeV scale. Both are consistent with current bounds and are attractive for future experimental searches at the LHC and future colliders. Depending on the hypercharge of the vector-like quarks, hadrons made of them are color-neutral bound states which would be interesting Dark Matter candidates.

• Higgs-confinement transitions in QCD from symmetry protected topological phases

  Thomas T. Dumitrescu, Po-Shen Hsin

  SciPost Phys. 17, 093 (2024) · published 26 September 2024 | Toggle abstract · pdf

  In gauge theories with fundamental matter there is typically no sharp way to distinguish confining and Higgs regimes, e.g. using generalized global symmetries acting on loop order parameters. It is standard lore that these two regimes are continuously connected, as has been explicitly demonstrated in certain lattice and continuum models. We point out that Higgsing and confinement sometimes lead to distinct symmetry protected topological (SPT) phases -- necessarily separated by a phase transition -- for ordinary global symmetries. We present explicit examples in 3+1 dimensions, obtained by adding elementary Higgs fields and Yukawa couplings to QCD while preserving parity $\mathsf{P}$ and time reversal $\mathsf{T}$. In a suitable scheme, the confining phases of these theories are trivial SPTs, while their Higgs phases are characterized by non-trivial $\mathsf{P}$- and $\mathsf{T}$-invariant theta-angles $\theta_f, \theta_g = \pi$ for flavor or gravity background gauge fields, i.e. they are topological insulators or superconductors. Finally, we consider conventional three-flavor QCD (without elementary Higgs fields) at finite $U(1)_B$ baryon-number chemical potential $\mu_B$, which preserves $\mathsf{P}$ and $\mathsf{T}$. At very large $\mu_B$, three-flavor QCD is known to be a completely Higgsed color superconductor that also spontaneously breaks $U(1)_B$. We argue that this high-density phase is in fact a gapless SPT, with a gravitational theta-angle $\theta_g = \pi$ that safely co-exists with the $U(1)_B$ Nambu-Goldstone boson. We explain why this SPT motivates unexpected transitions in the QCD phase diagram, as well as anomalous surface modes at the boundary of quark-matter cores inside neutron stars.

• Sifting composite from elementary models at FCCee and CePC

  Giacomo Cacciapaglia, Aldo Deandrea, Abhishek M. Iyer, Andres Pinto

  SciPost Phys. 14, 170 (2023) · published 26 June 2023 | Toggle abstract · pdf

  New Physics models with either an elementary or composite origin are often associated with a similar imprint in a direct search at colliders, case in point being the production of a light pseudoscalar in association with a monochromatic photon from the decay of a Z boson at future $e+e-$ colliders. We exploit the correlation between the discovery of a signal in the Z decays and electroweak precision measurements as a tool to distinguish a composite model from an elementary scalar one. Our results offer an appealing and rich physics case for future colliders and demonstrate how a lepton collider at the Z mass can be a discovery machine for new physics in the Higgs sector.

• Variational quantum gate optimization at the pulse level

  Sean Greenaway, Francesco Petiziol, Hongzheng Zhao, Florian Mintert

  SciPost Phys. 16, 082 (2024) · published 22 March 2024 | Toggle abstract · pdf

  We experimentally investigate the viability of a variational quantum gate optimization protocol informed by the underlying physical Hamiltonian of fixed-frequency transmon qubits. Through the successful experimental optimization of two and three qubit quantum gates the utility of the scheme for obtaining gates based on static effective Hamiltonians is demonstrated. The limits of such a strategy are investigated through the optimization of a time-dependent, Floquet-engineered gate, however parameter drift is identified as a key limiting factor preventing the implementation of such a scheme which the variational optimization protocol is unable to overcome.

• Disorder in AdS$_3$/CFT$_2$

  Moritz Dorband, Daniel Grumiller, René Meyer, Suting Zhao

  SciPost Phys. 16, 017 (2024) · published 18 January 2024 | Toggle abstract · pdf

  We perturbatively study marginally relevant quenched disorder in AdS$_3$/CFT$_2$ to second order in the disorder strength. Using the Chern-Simons formulation of AdS$_3$ gravity for the Poincaré patch, we introduce disorder via the chemical potentials. We discuss the bulk and boundary properties resulting from the disorder-averaged metric. The disorder generates a small mass and angular momentum. In the bulk and the boundary, we find unphysical features due to the disorder average. Motivated by these features, we propose a Poincaré-Lindstedt-inspired resummation method. We discuss how this method enables us to remove all of the unphysical features and compare with other approaches to averaging.

• Relative cluster entropy for power-law correlated sequences

  Anna Carbone, Linda Ponta

  SciPost Phys. 13, 076 (2022) · published 30 September 2022 | Toggle abstract · pdf

  We propose an information-theoretical measure, the \textit{relative cluster entropy} $\mathcal{D_{C}}[P \| Q] $, to discriminate among cluster partitions characterised by probability distribution functions $P$ and $Q$. The measure is illustrated with the clusters generated by pairs of fractional Brownian motions with Hurst exponents $H_1$ and $H_2$ respectively. For subdiffusive, normal and superdiffusive sequences, the relative entropy sensibly depends on the difference between $H_1$ and $H_2$. By using the \textit{minimum relative entropy} principle, cluster sequences characterized by different correlation degrees are distinguished and the optimal Hurst exponent is selected. As a case study, real-world cluster partitions of market price series are compared to those obtained from fully uncorrelated sequences (simple Browniam motions) assumed as a model. The \textit{minimum relative cluster entropy} yields optimal Hurst exponents $H_1=0.55$, $H_1=0.57$, and $H_1=0.63$ respectively for the prices of DJIA, S\&P500, NASDAQ: a clear indication of non-markovianity. Finally, we derive the analytical expression of the relative cluster entropy and the outcomes are discussed for arbitrary pairs of power-laws probability distribution functions of continuous random variables.

• Importance of the X-ray edge singularity for the detection of relic neutrinos in the PTOLEMY project

  Zhiyang Tan, Vadim Cheianov

  SciPost Phys. 17, 022 (2024) · published 26 July 2024 | Toggle abstract · pdf

  Direct detection of relic neutrinos in a beta-decay experiment is an ambitious goal that has long been beyond the reach of available technology. One of the most challenging practical difficulties for such an experiment is managing a large amount of radioactive material without compromising the energy resolution required to distinguish useful events from the substantial beta-decay background. The PTOLEMY project offers an innovative solution to this problem by depositing radioactive material on graphene. While this approach is expected to address the main challenge, it introduces new issues due to the proximity of the beta decayers to a solid-state system. In this work, we focus on the effect of the shakeup of the graphene electron system caused by a beta-decay event. We calculate the distortion of the relic neutrino peaks resulting from this shakeup, analyze the impact of the distortion on the visibility of neutrino capture events, and discuss potential technological solutions to enhance the visibility of these events.