Past singularities in phantom theories

TL;DR

This paper investigates the nature of past singularities in phantom dark energy models, revealing finite past causal geodesics, diverging curvature along geodesics, and the impact of observer momentum on perceived duration to the Big Rip.

Contribution

It demonstrates that FLRW models with dark energy have finite pasts, analyzes curvature behavior along geodesics, and explores how observer momentum affects the perceived timeline to the Big Rip.

Findings

Causal geodesics cannot be extended beyond a finite proper time in these models.

Curvature along geodesics diverges as one approaches the past.

The proper time to the Big Rip can be made arbitrarily short by increasing observer momentum.

Abstract

FLRW models filled with just dark energy are shown to have a finite past, since causal geodesics cannot be extended beyond a certain proper time. It is shown that curvature measured along causal geodesics becomes infinity on travelling to the past, though curvature scalars tend to zero. Furthermore the time measured by free-falling observers from coincidence time to Big Rip is shown to be as short as wished by increasing their linear momentum.