Physical Review A
Privman-Fisher hypothesis on finite systems: Verification in the case of a relativistic Bose gas with pair production
Surjit Singh, Raj K. Pathria
Abstract
The Privman-Fisher hypothesis on the singular part of the free-energy density of a finite system, near the bulk critical point T=${T}_{c}$, is examined in the context of an ideal relativistic Bose gas confined to a cuboidal enclosure (${L}_{1}$\ifmmode\times\else\texttimes\fi{}${L}_{2}$\ifmmode\times\else\texttimes\fi{}${L}_{3}$) under periodic boundary conditions. Taking into account the possibility of particle-antiparticle pair production in the system, explicit expressions are derived for the free energy, the specific heat, and the condensate density at temperatures close to ${T}_{c}$, and the special cases of a cube, a square channel and a film are investigated at length. The various predictions of the Privman-Fisher hypothesis are fully borne out and the scaling functions governing the critical behavior of the system are found to be universal---irrespective of the severity of the relativistic effects. The influence of the latter enters only through the nonuniversal scale factors, ${C}_{1}$ and ${C}_{2}$, which depend on the particle mass m and density \ensuremath{\rho} as well.