Acceleration of the Universe, String Theory and a Varying Speed of Light

TL;DR

This paper explores how a varying speed of light in an accelerating universe can resolve the horizon problem, enabling consistent string theory formulations by eliminating future horizons.

Contribution

It proposes a novel approach where the speed of light varies to remove future horizons, addressing a key obstacle in string theory related to accelerating universes.

Findings

Varying speed of light can eliminate future horizons.

This approach allows for a consistent S-matrix formulation in string theory.

Addresses the crisis posed by accelerating universe models for quantum theories.

Abstract

The existence of future horizons in spacetime geometries poses serious problems for string theory and quantum field theories. The observation that the expansion of the universe is accelerating has recently been shown to lead to a crisis for the mathematical formalism of string and M-theories, since the existence of a future horizon for an eternally accelerating universe does not allow the formulation of physical S-matrix observables. Postulating that the speed of light varies in an expanding universe in the future as well as in the past can eliminate future horizons, allowing for a consistent definition of S-matrix observables.