Pressure dependence of phonon populations and non-standard quasiadditive integrals of motion

The existing equilibrium statistical physics is based on application of standard quasiadditive integrals of motion, which include energy, momentum, rotation momentum, and number of particles. It is shown that this list is far from complete and that any quasiadditive dynamic variable can be mapped to corresponding quasiadditive integral of motion. As a result an ensemble with a given external pressure is constructed. It provides the first example of the distribution in which phonon populations depend on pressure differently than in the canonical Gibbs ensemble. Obtained results indicate the need to continue the studies of phonon populations based on Raman scattering, which were fulfilled earlier in LFTI and initiated this work.