Temperature, Topology and Quantum Fields

This thesis uses Path Integrals and Green's Functions to study Gravity, Quantum Field Theory and Statistical Mechanics, particularly with respect to: finite temperature quantum systems of different spin in gravitational fields; finite temperature interacting quantum systems in perturbative regime; self-interacting fermi models in non-trivial space-time of different dimensions; non-linear quantum models at finite temperatures in a background curved space-time; 3-D topological field models in non-trivial space-time and at finite temperatures; thermal quantum systems in a background curved space-time. Results include: Non-Equivalence of Inertial and Gravitational Mass.