Cosmological evolution with brane-bulk energy exchange

Abstract

The consequences for the brane cosmological evolution of energy exchange between the brane and the bulk are analyzed in detail, in the context of a non-factorizable background geometry with vanishing effective cosmological constant on the brane. A rich variety of brane cosmologies is obtained, depending on the precise mechanism of energy transfer, the equation of state of brane-matter and the spatial topology. An accelerating era is generically a feature of our solutions. In the case of low-density flat universe more dark matter than in the conventional FRW picture is predicted. Spatially compact solutions are found to delay their re-collapse.

Brane‐bulk energy exchange and cosmological acceleration

“…This is possible if we assume that the diagonal elements of the various contributions to the energy-momentum tensor satisfy the schematic inequality kkttz [6] …”

“…We will restrict ourselves for simplicity to the 4d regime. For the non-linear analysis we refer the reader to kkttz [6]. For a fixed point equations ( a11 2.35), ( aa11 2.36) must have a time-independent solution, without necessarily requiring w = −1 (λ = k = 0).…”

“…Here, I will mostly focus on the approach described in kkttz [6]. In any theory, where gravity is higher-dimensional classically (around flat space), a mechanism must be invoked to explain why observable gravity is four-dimensional at experimentally verifiable distances.…”

“…In all such realizations, the 4d graviton is accompanied by KK modes that propagate in the bulk and can thus mediate energy-exchanging processes between brane and bulk matter. Such processes are important because on the one hand they provide stringent constraints on brane-world models and on the other as it was argued in kkttz [6] they may generate interesting cosmological effects.…”

Late acceleration andw=−1crossing in induced gravity

“…Several examples of non-standard scaling are known [20,21,22]. Also, the energy exchange between the brane and the bulk may result in a complicated cosmological expansion [23,24,25].…”