Accelerating universes driven by bulk particles

TL;DR

This paper models our universe as a 3d domain wall in 5d space, explaining inflation and late-time acceleration through bulk particle interactions and internal dark matter structures, linking to string/M-theory.

Contribution

It introduces a novel framework where bulk particles and internal dark matter structures drive universe expansion, connecting domain wall dynamics to string theory.

Findings

Expansion is exponential at early times and polynomial later.

Reflection coefficient depends on internal dark matter structures.

Increased internal structures accelerate domain wall expansion.

Abstract

We consider our universe as a 3d domain wall embedded in a 5d dimensional Minkowski space-time. We address the problem of inflation and late time acceleration driven by bulk particles colliding with the 3d domain wall. The expansion of our universe is mainly related to these bulk particles. Since our universe tends to be permeated by a large number of isolated structures, as temperature diminishes with the expansion, we model our universe with a 3d domain wall with increasing internal structures. These structures could be unstable 2d domain walls evolving to fermi-balls which are candidates to cold dark matter. The momentum transfer of bulk particles colliding with the 3d domain wall is related to the reflection coefficient. We show a nontrivial dependence of the reflection coefficient with the number of internal dark matter structures inside the 3d domain wall. As the population of such structures increases the velocity of the domain wall expansion also increases. The expansion is exponential at early times and polynomial at late times. We connect this picture with string/M-theory by considering BPS 3d domain walls with structures which can appear through the bosonic sector of a five-dimensional supergravity theory.