Finite field dependent BRST symmetry and its applications

Due to the lack of hard empirical data, symmetry principles have been proved to be the most invaluable tools in describing physical phenomenon. Gauge field theories (based on the local gauge invariance of the Lagrangian density of the theories) have enormous importance in describing all the fundamental interactions of nature and play the central role in understanding the present state of the art of modern particle physics. The standard model of particle physics which describes strong, weak and electromagnetic interactions on the same footing is a non-Abelian gauge theory.