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There is a dichotomy in the nonequilibrium dynamics of quantum many body systems. In the presence of integrability, expectation values of local operators equilibrate to values described by a generalized Gibbs ensemble, which retains…

Strongly Correlated Electrons · Physics 2019-05-15 Neil J. Robinson , Andrew J. A. James , Robert M. Konik

We investigate off-diagonal matrix elements of local operators in integrable spin chains, focusing on the isotropic spin-$1/2$ Heisenberg chain ($XXX$ chain). We employ state-of-the-art Algebraic Bethe Ansatz results, which allow us to…

Statistical Mechanics · Physics 2026-02-18 Federico Rottoli , Vincenzo Alba

The eigenstate thermalization hypothesis (ETH) describes the properties of diagonal and off-diagonal matrix elements of local operators in the eigenenergy basis. In this work, we propose a relation between (i) the singular behaviour of the…

Quantum Physics · Physics 2025-03-18 Luca Capizzi , Jiaozi Wang , Xiansong Xu , Leonardo Mazza , Dario Poletti

We investigate the extent to which the eigenstate thermalization hypothesis~(ETH) is valid or violated in the non-integrable and the integrable spin-$1/2$ XXZ chain. We perform the energy-resolved analysis of the statistical properties of…

Statistical Mechanics · Physics 2021-02-03 Jae Dong Noh

Correlation functions of most composite operators decay exponentially with time at non-zero temperature, even in free field theories. This insight was recently codified in an OTH (operator thermalisation hypothesis). We reconsider an early…

High Energy Physics - Theory · Physics 2020-10-28 Julius Engelsöy , Jorge Larana-Aragon , Bo Sundborg , Nico Wintergerst

The Eigenstate Thermalization Hypothesis (ETH) explains emergence of the thermodynamic equilibrium by assuming a particular structure of observable's matrix elements in the energy eigenbasis. Schematically, it postulates that off-diagonal…

Statistical Mechanics · Physics 2022-05-11 Jiaozi Wang , Mats H. Lamann , Jonas Richter , Robin Steinigeweg , Anatoly Dymarsky , Jochen Gemmer

A non-hermitian deformation of the one-dimensional transverse Ising model is shown to have the property of quasi-hermiticity. The transverse Ising chain is obtained from the starting non-hermitian Hamiltonian through a similarity…

Statistical Mechanics · Physics 2009-11-09 Tetsuo Deguchi , Pijush K. Ghosh

The Eigenstate Thermalization Hypothesis (ETH) represents a cornerstone in the theoretical understanding of the emergence of thermal behavior in closed quantum systems. The ETH asserts that expectation values of simple observables in energy…

Statistical Mechanics · Physics 2024-05-15 Giorgio Cipolloni , Jonah Kudler-Flam

The eigenstate thermalisation hypothesis (ETH) is a statistical characterisation of eigen-energies, eigenstates and matrix elements of local operators in thermalising quantum systems. We develop an ETH-like ansatz of a partially…

Quantum Physics · Physics 2022-08-01 Philip JD Crowley , Anushya Chandran

Isolated quantum systems typically approach thermal equilibrium as described by the Eigenstate Thermalization Hypothesis (ETH). Going beyond this involves either higher order correlators (full thermalization) or the formation of state…

Quantum Physics · Physics 2026-05-01 Tabea Herrmann , Felix Fritzsch , Arnd Bäcker

The eigenstate thermalization hypothesis (ETH) is one of the cornerstones in our understanding of quantum statistical mechanics. The extent to which ETH holds for nonlocal operators is an open question that we partially address in this…

Statistical Mechanics · Physics 2019-02-27 Ivan M. Khaymovich , Masudul Haque , Paul A. McClarty

We study thermalization of transverse field Ising chain with power law decaying interaction $\sim 1/r^{\alpha}$ following a global quantum quench of the transverse field to two different dynamical regimes. We quantify the thermalization…

Statistical Mechanics · Physics 2025-01-13 Nishan Ranabhat , Mario Collura

Quantum thermalization is well understood via the Eigenstate Thermalization Hypothesis (ETH). The general form of ETH, describing all the relevant correlations of matrix elements, may be derived on the basis of a `typicality' argument of…

Statistical Mechanics · Physics 2023-03-30 Silvia Pappalardi , Laura Foini , Jorge Kurchan

If we prepare an isolated, interacting quantum system in an eigenstate and perturb a local observable at an initial time, its expectation value will relax towards a thermal expectation value, even though the time evolution of the system is…

Quantum Physics · Physics 2024-06-04 Tobias Helbig , Tobias Hofmann , Ronny Thomale , Martin Greiter

We develop a class of matrix models which implement and formalize the `eigenstate thermalization hypothesis' (ETH) and point out that in general these models must contain non-Gaussian corrections, already in order to correctly capture…

High Energy Physics - Theory · Physics 2023-01-06 Daniel Louis Jafferis , David K. Kolchmeyer , Baur Mukhametzhanov , Julian Sonner

In a recent Letter [PhysRevLett.119.030601 (2017), arXiv:1702.08227], Shiraishi and Mori claim to provide a general method for constructing local Hamiltonians that do not exhibit eigenstate thermalization. We argue that the claim is based…

Statistical Mechanics · Physics 2018-07-19 Rubem Mondaini , Krishnanand Mallayya , Lea F. Santos , Marcos Rigol

By developing a semi-classical analysis based on the Eigenstate Thermalization Hypothesis, we determine the long time behavior of a large spin evolving with a nonlinear Hamiltonian. Despite integrable classical dynamics, we find the…

Quantum Physics · Physics 2020-11-10 Shane P. Kelly , Eddy Timmermans , S. -W. Tsai

We study the quantum relaxation of the two-dimensional transverse-field Ising model after global quenches with a real-time variational Monte Carlo method and address the question whether this non-integrable, two-dimensional system…

Statistical Mechanics · Physics 2017-01-18 Benjamin Blaß , Heiko Rieger

The Eigenstate Thermalization Hypothesis (ETH) provides a sufficient condition for thermalization of isolated quantum systems. While the standard ETH is formulated in the absence of degeneracy, physical systems often possess symmetries that…

High Energy Physics - Theory · Physics 2026-05-27 Soma Onoda , Osamu Fukushima , Ryusuke Hamazaki , Okuto Morikawa

An isolated quantum system is said to thermalize if ${\rm Tr} (A \rho(t)) \to {\rm Tr} (A \rho_{\rm eq})$ for time $t \to \infty$. Here $\rho(t)$ is the time-dependent density matrix of the system, $\rho_{\rm eq}$ is the time-independent…

Quantum Physics · Physics 2024-04-22 Hans A. Weidenmüller