Investigations In Higher Dimensional Gravity Theory

TL;DR

This thesis explores higher-dimensional gravity with brane worlds in supergravity, revealing how bulk effects influence cosmological evolution, including inflation and acceleration, through complex structure moduli of Calabi-Yau manifolds.

Contribution

It provides new solutions linking brane cosmology to Calabi-Yau complex structure moduli, demonstrating bulk effects can explain universe's inflation and acceleration without additional fields.

Findings

Solutions exhibit early inflation and late acceleration.

Cosmological history explained by bulk effects alone.

Analytic and numeric solutions constructed.

Abstract

In this thesis we study BPS 3-brane embedded in five dimensional $\mathcal{N}=2$ supergravity. We have found that when modeling our universe as a brane world filled with matter, radiation and/or pure energy, the time evolution of the brane world is strongly correlated to the complex structure moduli of the underlying Calabi-Yau manifold. Moreover most solutions exhibit an early time inflation and late time acceleration, which means our universe's whole cosmological history may be explained by only the bulk effects, without introducing an inflation field or even cosmological constant term in some cases. The constructed solutions are numeric and have been manifested analytically as well. Finally, since our solutions to the field equations are constrained by how far we know about the Calabi-Yau manifold itself, we have studied the solely time dependence of the complex structure moduli and the metric of the complex structure space in case the dimension of the complex structure space of the Calabi-Yau manifold $h_{(2,1)} = 1$ .