Graduate School in Nonlinear Science

Sponsored by the Danish Research Academy

MIDIT                               OFD                           CATS
Modelling, Nonlinear Dynamics       Optics and Fluid Dynamics     Chaos and Turbulence Studies
and Irreversible Thermodynamics     Risø National Laboratory      Niels Bohr Institute and 
Technical University of Denmark     Building 128                  Department of Chemistry
Building 321                        P.O. Box 49                   University of Copenhagen 
DK-2800 Lyngby                      DK-4000 Roskilde              DK-2100 Copenhagen Ø
Denmark                             Denmark                       Denmark


by Kim Ørskov Rasmussen
Center for Nonlinear Sciences
Los Alamos, USA

MIDIT-seminar 461

Tuesday August 24, 1999, 15.00 h
at MIDIT, IMM Building 305, room 027

Abstract: The statistical mechanics of the discrete nonlinear Schrödinger equation is studied by means of analytic and numerical techniques. The lower bound of the Hamiltonian permits the construction of standard Gibbsian equilibrium measures for positive temperatures. Beyond the T=infinity line, we identify a phase transition, through a discontinuity in the partition function. The phase transition is demonstrated to manifest itself in the creation of breather-like localized excitations. The interrelation between the statistical mechanics and the nonlinear dynamics of the system is explored numerically both in the positive and in the negative temperature regimes.