The concept of fidelity decay is discussed from the point of view of the scattering matrix, and the scattering fidelity is introduced as the parametric cross-correlation of a given S-matrix element,… (More)

Abstract. Using supersymmetry techniques analytical expressions for the average of the fidelity amplitude fǫ(τ) = 〈ψ(0)| exp(2πıHǫτ) exp(−2πıH0τ)|ψ(0)〉 are obtained, where the H0 and Hǫ are taken… (More)

The scattering matrix was measured for a flat microwave cavity with classically chaotic dynamics. The system can be perturbed by small changes of the geometry. We define the "scattering fidelity" in… (More)

The scattering matrix was measured for microwave cavities with two antennas. It was analyzed in the regime of overlapping resonances. The theoretical description in terms of a statistical scattering… (More)

We study the time evolution of fidelity in a dynamical many-body system, namely, a kicked Ising model, modified to allow for a time-reversal invariance breaking. We find good agreement with the… (More)

Recently it has been shown that time-reversal invariant systems with discrete symmetries may display, in certain irreducible subspaces, spectral statistics corresponding to the Gaussian-unitary… (More)

In this work several aspects of quantum chaos are studied in the time domain. The wave equation for flat microwave cavities is equivalent to the Schrödinger equation in quantum mechanics. Therefore… (More)

The two-fluid model of liquid helium is generalized to the case that the super-fluid fraction has a small entropy content. We present theoretical arguments in favour of such a small superfluid… (More)

This letter is based on the hypothesis of a small entropy content of the superfluid fraction of liquid helium. We show that such a superfluid entropy gives rise to a new sound mode in a ring-shaped… (More)