Executive Summary : | Boundary conditions are central to obtaining many semiclassical results in various contexts. Hawking radiation, the Unruh effect, Casimir effect, moving mirrors all utilize the selection of appropriate mode functions subject to pre-specified boundary conditions which typically are taken to be robustly defined. In context of Hawking radiation and the Unruh effect the horizon servres as the place where boundary conditions are typically imposed. These horizons are often used as a collection of disjoint set of boundary data with which mode functions of quantum fields are developed in the causally disjoint regions [1]. The Casimir effect and the moving mirrors directly employ vanishing/reflective boundary conditions to obtain modified quantum correlator structures [2]. In such analysis, the surface of boundary data is supposed to be fixed, given by calssical geometry as apt for semicalssical analysis. However, varoius characteristic features of the Cauchy surface may be identified having quantum character. A horizon for instance may not be a classically defined null surface but may be subject to light cone fluctuations. Similarly the surfaces of reflective/vanishing boundary conditions will in principle be subject to inherent quantum fluctuations. Therefore, an aggregate effect of such fluctuations should be the realistic physical output. |