Item

Abstract

In this thesis, we study certain physically motivated systems in which large-N physics and gauge redundancy play an important role. Recently, a new upper bound on microstate entropy was proposed and was demonstrated that the objects saturating this bound, so-called "saturons", share all the key properties of a black hole. This finding indicates that black hole properties are not specific to gravity and are universal to all saturons. We give the explicit check to this idea by showing that the maximal entropy bound states in Gross-Neveu model are saturons and carry the black hole like properties. The power of large-N physics and the asymptotic freedom of the theory allows us to give a very clean understanding of the connection. We thus uncover the foundation of black hole's underlying quantum physics within a fully calculable model. Secondly, we discuss a gauge redundant formulation of axion and demonstrate its insensitivity towards UV-physics. Finally, we explicitly construct some important BRST invariant states in electrodynamics and in large-N gravity, with particular implication of formulating de Sitter space as a coherent state constructed on top of the Minkowski vacuum. This construction is essential for understanding the viability and properties of de-Sitter like states within the S-matrix formulation of quantum gravity, currently the only known formulation. This formulation implies that de Sitter cannot be regarded as a vacuum. Instead, it must be represented as a coherent state that evolves in time non-trivially. This has important implications for physics of dark energy.