Poster presented by Jani Lukkarinen

Topic: Theoretical Developments

Lattice methods in microcanonical quantum statistics

Abstract: Canonical ensemble has proven to be the most efficient and often the easiest way of applying quantum statistics and, as Euclidean quantum field theory, it shows up also in the lattice quantum field simulations. Nevertheless, the canonical ensemble is a sensible approximation only for those physical systems which have relatively large total energy fluctuations and ``sufficiently many particles''. For small, more isolated systems, the microcanonical ensemble or one of its variants should be used. These, however, can all be approximated by the Gaussian ensemble and here we present a procedure for the lattice evaluation of the Gaussian expectation values. If the system is not too far from being thermodynamical, it is possible to use the canonical ensemble as an approximation of the Gaussian one and we show how lattice methods can be employed in the evaluation of correction terms to the canonical expectation values.

Massimo Campostrini, campo@mailbox.difi.unipi.it