Hubble Law and Brane Matter after Ekpyrosis

TL;DR

This paper investigates brane matter in the ekpyrotic scenario, showing that positive brane tension is necessary for standard gravity and exploring conditions for realistic cosmology with small corrections.

Contribution

It demonstrates the conditions under which standard gravity and cosmology can be achieved in the ekpyrotic brane model, considering brane tension and extra-dimensional dynamics.

Findings

Positive brane tension is required for standard gravity.

Time-dependent brane matter is restricted unless certain constraints are relaxed.

Approximate standard cosmology is possible with small corrections from extra-dimensional effects.

Abstract

We study brane matter in the ekpyrotic scenario and observe that in order to obtain standard gravity on the visible brane, the tension of the visible brane should be positive. If the sizes of both the fifth dimension and the Calabi-Yau threefold are fixed, the Israel junction conditions do not allow time-dependent brane matter. Relaxing this constraint, it is possible to obtain approximately standard cosmology on the visible brane, with small corrections due to possible time-dependence of the Calabi-Yau threefold.