  In this thesis we study some aspects of cosmology and black holes using field
theoretic techniques. In second chapter, we present Lagrangian formulation for
the non-relativistic as well as relativistic generalized Chaplygin gas (GCG).
In rest of the thesis we discuss alternative approaches to compute the fluxes
of Hawking radiation. These methods are based on covariant gauge/gravitational
anomalies and chiral effective action. We also discuss a criterion to
differentiate various black hole vacua within the framework of covariant
anomaly approach.
