Large deviations for ideal quantum systems

We consider a general d-dimensional quantum system of non-interacting parti cles in a very large (formally infinite) container. We prove that, in equil ibrium, the fluctuations in the density of particles in a subdomain Lambda of the container are described by a large deviation function related to the pressure of the system. That is, untypical densities occur with a probabil ity exponentially small in the volume of Lambda, with the coefficient in th e exponent given by the appropriate thermodynamic potential. Furthermore, s mall fluctuations satisfy the central limit theorem. (C) 2000 American Inst itute of Physics. [S0022-2488(00)01803-X].