arXiv subjects
Publications and source records attributed to Stefan V. Mashkevich.
We study the possibility of existence of bound states for two interacting He-4 atoms. It is shown that for some potentials, there exist not only discrete levels but also bands akin to those in the Kronig--Penney model.
Quantum decoherence is of primary importance for relaxation to an equilibrium distribution and, accordingly, for equilibrium processes. We demonstrate how coherence breaking implies evolution to a microcanonical distribution (``microcanonical postulate'') and, on that ground, consider an adiabatic process, in which there is no thermostat. We stress its difference from a zero-polytropic process, i.e., a process with zero heat capacity but involving a thermostat. We find the distribution for the adiabatic process and show that (i) in the classical limit this distribution is canonical, (ii) for macroscopic systems, the mean values of energy for adiabatic and zero-polytropic processes are the same, but its fluctuations are different, and (iii) in general, adiabatic and zero-polytropic processes are different, which is particularly essential for mesoscopic systems; for those latter, an adiabatic process is in general irreversible.
The general notion of distance dependent statistics in anyon-like systems is discussed. The two-body problem for such statistics is considered, the general formula for the second virial coefficient is derived and it is shown that in the limiting cases it reproduces the known results for ideal anyons.
Using the symmetry properties of the three-anyon spectrum, we obtain exactly the multiplicities of states with given energy and angular momentum. The results are shown to be in agreement with the proper quantum mechanical and semiclassical considerations, and the unexplained points are indicated.