2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/50931We consider the phase structure of a pure compact U(1) gauge theory in four dimensions at finite temperature by treating this system as a perturbative deformation of the topological model. Phases of a gauge theory can be investigated from the phase structure of the topological model. The thermal pressure of the topological model has been calculated, from which its phase structure can be derived. We have obtained phases of a compact U(1) gauge theory. Moreover, the critical-line equation has been explicitly evaluated.4 pages, 5 figures, REVTeX4, v2:several errors are corrected and references are addedHigh Energy Physics - TheoryHigh Energy Physics - Phenomenologytext