From the Kubo formula to variable range hopping

Consider a multichannel closed ring with disorder. In the semiclassical treatment its conductance is given by the Drude formula. Quantum mechanics challenge this result both in the limit of strong disorder (eigenstates are not quantum-ergodic in real space) and in the limit of weak disorder (eigenstates are not quantum-ergodic in momentum space). Consequently the analysis of conductance requires going beyond linear response theory, leading to a resistor network picture of transitions between energy levels. We demonstrate that our semi-linear response theory provides a firm unified framework from which the "hopping" phenomenology of Mott can be derived.Comment: 5 pages, published version with an extended concluding paragrap

Neutrino neutral reaction on 4He, effects of final state interaction and realistic NN force

The inelastic neutral reaction of neutrino on 4He is calculated microscopically, including full final state interaction among the four nucleons. The calculation is performed using the Lorentz integral transform (LIT) method and the hyperspherical-harmonic effective interaction approach (EIHH), with a realistic nucleon-nucleon interaction. A detailed energy dependent calculation is given in the impulse approximation. With respect to previous calculations, this work predicts an increased reaction cross-section by 10%-30% for neutrino temperature up to 15 MeV.Comment: 4 pages, 2 fig

Monte--Carlo Thermodynamic Bethe Ansatz

We introduce a Monte--Carlo simulation approach to thermodynamic Bethe ansatz (TBA). We exemplify the method on one particle integrable models, which include a free boson and a free fermions systems along with the scaling Lee--Yang model (SLYM). It is confirmed that the central charges and energies are correct to a very good precision, typically 0.1% or so. The advantage of the method is that it enables the calculation of all the dimensions and even the particular partition function.Comment: 22 pages. Added a footnote and realizations for the minimal models. Fortran program, mont-s.f90, available from the source lin

Quantum pumping: The charge transported due to a translation of a scatterer

The amount of charge which is pushed by a moving scatterer is $dQ = -G dX$, where $dX$ is the displacement of the scatterer. The question is what is $G$. Does it depend on the transmission $g_0$ of the scatterer? Does the answer depend on whether the system is open (with leads attached to reservoirs) or closed? In the latter case: what are the implications of having ``quantum chaos" and/or coupling to to the environment? The answers to these questions illuminate some fundamental aspects of the theory of quantum pumping. For the analysis we take a network (graph) as a model system, and use the Kubo formula approach.Comment: 4 pages, 2 figures, minor changes, to be published in PRE (Rapid

Semiclassical Description of Tunneling in Mixed Systems: The Case of the Annular Billiard

We study quantum-mechanical tunneling between symmetry-related pairs of regular phase space regions that are separated by a chaotic layer. We consider the annular billiard, and use scattering theory to relate the splitting of quasi-degenerate states quantized on the two regular regions to specific paths connecting them. The tunneling amplitudes involved are given a semiclassical interpretation by extending the billiard boundaries to complex space and generalizing specular reflection to complex rays. We give analytical expressions for the splittings, and show that the dominant contributions come from {\em chaos-assisted}\/ paths that tunnel into and out of the chaotic layer.Comment: 4 pages, uuencoded postscript file, replaces a corrupted versio

Quantum Stirring in low dimensional devices

A circulating current can be induced in the Fermi sea by displacing a scatterer, or more generally by integrating a quantum pump into a closed circuit. The induced current may have either the same or the opposite sense with respect to the "pushing" direction of the pump. We work out explicit expressions for the associated geometric conductance using the Kubo-Dirac monopoles picture, and illuminate the connection with the theory of adiabatic passage in multiple path geometry.Comment: 6 pages, 5 figures, improved versio