Off-Diagonal Metrics and Anisotropic Brane Inflation

TL;DR

This paper investigates how off-diagonal metrics influence anisotropic reheating in brane-world cosmology, revealing that such metrics can produce anisotropic dark radiation and alter entropy production processes before nucleosynthesis.

Contribution

It introduces the role of off-diagonal bulk metrics and anholonomic frames in brane-world reheating, highlighting their impact on dark radiation and entropy production.

Findings

Significant anisotropic dark radiation can be produced during reheating.

Off-diagonal metric components modify entropy production processes.

Additional entropy production is generally needed before nucleosynthesis.

Abstract

We study anisotropic reheating (entropy production) on 3D brane from a decaying bulk scalar field in the brane-world picture of the Universe by considering off-diagonal metrics and anholonomic frames. We show that a significant amount of, in general, anisotropic dark radiation is produced in this process unless only the modes which satisfy a specific relation are excited. We conclude that subsequent entropy production within the brane is required in general before primordial nucleosynthesis and that the presence of off-diagonal components (like in the Salam, Strathee and Petracci works) of the bulk metric modifies the processes of entropy production which could substantially change the brane-world picture of the Universe.