2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/91980We discuss radiation fields in a compact space of finite size instead of that in a cavity for investigating the coupled atom-radiation field system. Representations of $T(1)\times SO(4)$ group are used to give a formulation for kinematics of the radiation fields. The explicit geometrical parameter dependence of statistical properties of radiation fields is obtained. Results show remarkable differences from that of the black-body radiation system in free space.LaTeX2e plain file of 10 pages, 1 eps figureQuantum Physicstext