Will the tachyonic Universe survive the Big Brake?

TL;DR

This paper explores a tachyonic universe model that can evolve into a Big Brake singularity, analyzing its observational signatures, geodesic behavior, and ultimate fate of recollapse, with implications for future cosmological observations.

Contribution

It introduces a tachyon scalar field model that predicts a Big Brake singularity and examines its observational viability and cosmic evolution, including geodesic continuation and recollapse.

Findings

Some evolutions lead to a Big Brake observable with future data.

The Big Brake occurs at finite scale factor with diverging deceleration.

The universe will eventually recollapse into a Big Crunch.

Abstract

We investigate a Friedmann universe filled with a tachyon scalar field, which behaves as dustlike matter in the past, while it is able to accelerate the expansion rate of the universe at late times. The comparison with type Ia supernovae (SNIa) data allows for evolutions driving the universe into a Big Brake. Some of the evolutions leading to a Big Brake exhibit a large variation of the equation of state parameter at low redshifts which is potentially observable with future data though hardly detectable with present SNIa data. The soft Big Brake singularity occurs at finite values of the scale factor, vanishing energy density and Hubble parameter, but diverging deceleration and infinite pressure. We show that the geodesics can be continued through the Big Brake and that our model universe will recollapse eventually in a Big Crunch. Although the time to the Big Brake strongly depends on the present values of the tachyonic field and of its time derivative, the time from the Big Brake to the Big Crunch represents a kind of invariant timescale for all field parameters allowed by SNIa.