arXiv subjects

Felix Izrailev

Publications and source records attributed to Felix Izrailev.

3 recordsLinked to original sources

arXiv2021

Spectrum statistics in the integrable Lieb-Liniger model

We address the old and widely debated question of the statistical properties of integrable quantum systems, through the analysis of the paradigmatic Lieb-Liniger model. This quantum many-body model of 1-d interacting bosons allows for the rigorous determination of energy spectra via the Bethe ansatz approach and our interest is understanding whether Poisson statistics is a characteristic feature of this model. Using both analytical and numerical studies we show that the properties of spectra strongly depend on whether the analysis is done for a full energy spectrum or for a single subset with fixed total momentum. We show that the Poisson distribution of spacing between nearest-neighbor energies can occur only for a set of energy levels with fixed total momentum, for neither too large nor too weak interaction strength, and for sufficiently high energy. On the other hand, when studying long-range correlations between energy levels, we found strong deviations from the predictions given by a Poisson process.

quant-ph↗

arXiv2020

Process of equilibration in many-body isolated systems: Diagonal versus thermodynamic entropy

As recently manifested , the quench dynamics of isolated quantum systems consisting of a finite number of particles, is characterized by an exponential spreading of wave packets in the many-body Hilbert space. This happens when the inter-particle interaction is strong enough, thus resulting in a chaotic structure of the many-body eigenstates considered in an unperturbed basis. The semi-analytical approach used here, allows one to estimate the rate of the exponential growth as well as the relaxation time, after which the equilibration (thermalization) emerges. The key ingredient parameter in the description of this process is the width $Γ$ of the Local Density of States (LDoS) defined by the initially excited state, the number of particles and the interaction strength. In this paper we show that apart from the meaning of $Γ$ as the decay rate of survival probability, the width of the LDoS is directly related to the diagonal entropy and the latter can be linked to the thermodynamic entropy of a system equilibrium state emerging after the complete relaxation. The analytical expression relating the two entropies is derived phenomenologically and numerically confirmed in a model of bosons with random two-body interaction, as well as in a deterministic model which becomes completely integrable in the continuous limit.

nlin.CD↗

arXiv1997

Quantum-Classical Correspondence in Energy Space: Two Interacting Spin-Particles

The Hamiltonian conservative system of two interacting particles has been considered both in classical and quantum description. The quantum model has been realized using a symmetrized two-particle basis reordered in the unperturbed energy. Main attention is paid to the structure of chaotic eigenfunctions (EF) and to the local spectral density of states (LDOS). A remarkable correspondence has been found for the shapes of EF and LDOS in the energy representation, to their classical counterparts. Comparison with the Band Random Matrix theory predictions has revealed quite significant differences which are due to dynamical nature of the model. On the other hand, a partial agreement is found by inserting randomness `` ad hoc '' in the dynamical model for two-body matrix elements. This shows that, at least for small number of particles, care must be taken when classical correlations are neglected. The question of quantum localization in the energy space is discussed both for dynamical and random model.

chao-dyn↗