The brane universe as an open system

• Main Author: Jennings, D.
• Published: University of Cambridge 2007
• Subjects: 520
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.605097

Chapters 2 and 3 contain an analysis of the process of energy exchange between the brane universe and the bulk spacetime. In particular we focus on graviton emission from a general, asymmetric brane into a Schwarzschild Anti-de Sitter bulk, and consider the competing mechanism of bulk black holes radiating across the brane. We discuss the global structure of these spacetimes and impose experimental constraints on the time-varying dark radiation that appears in the Friedmann equation. Chapters 4 to 8 consider quantum effects that arise in the bulk spacetimes of branes. We make the observation that brane universe generally accelerate through their bulk spacetimes, and as such may be considered Unruh observers, subject to thermal excitations from a vacuum state. In particular, we focus on an accelerating brane in Anti de Sitter spacetime and compute the response function along its trajectory. It is found that modified thermal excitations occur along stationary trajectories with accelerations above the curvature scale of the bulk, with the modification dependent on the bulk curvature and the dimensionality of spacetime. We discuss the late-time asymptotic behaviour of this Unruh radiation and find that when the matter density on the brane shrinks to zero, the temperature of bulk spacetime coincides with the temperature of the brane. In addition, a brane-based view-point in presented in which the Unruh effect is recast as particle production on a lower dimensional spacetime. Chapter 8 is a discussion of how the bulk spacetime decoheres physics on the brane and breaks unitary time evolution.