Fidelity decay and entropy production in many-particle systems after random interaction quench

S. K. Haldar, N. D. Chavda, V. K. B. Kota

Published 2015-09-04Version 1

Fidelity decay and entropy production, with time, of a many particle system of fermions (or bosons) in a mean-field and quenched by a random two-body interaction is generated by a Hamiltonian that is represented by embedded Gaussian orthogonal ensemble of random matrices (for time-reversal and rotationally invariant systems) with one plus two-body interactions [EGOE(1+2)]. Numerical studies are carried out for a system of 8 fermions in 16 single particle states with the fermions carrying spin degree of freedom and also for a system with 10 bosons in 5 single particle states, by varying the strength of the interaction. Results for the fidelity decay compare well not only with the EGOE formula in the Gaussian domain but also with a new formula for the BW to Gaussian transition region. Applying the approximation suggested by Flambaum and Izrailev, formula for entropy production for EGOE(1+2) in the Gaussian region with extension into BW region is derived along with an analytical expression for the time $t_{sat}$ for onset of saturation of entropy. These EGOE results are in good agreement with numerical calculations. Finally, Fermion system shows significant spin dependence of the relaxation dynamics of the entropy.