This thesis consists of two parts. In the first part, which is expository, abstract theory of one-parameter operator is studied semi-groups. We develop in detail the necessary Banach space and Banach algebra theories of ...

The so-called Einstein-Aether theory is General Relativity coupled (at second derivative order) to a dynamical time-like unit vector field (the "Aether"). It is a Lorentz-violating theory and has gained much attention in ...