'The End'

TL;DR

This paper introduces a natural scalar field mechanism that predicts the universe will eventually collapse after a period of accelerated expansion, addressing the 'Why Now?' problem.

Contribution

It presents a simple, technically natural model with a linear potential scalar field that causes cosmic collapse after a prolonged acceleration phase, integrating vacuum energy sequestering.

Findings

The universe is predicted to end in a collapse after about 10 billion years.

The model's parameters are radiatively stable due to shift symmetry.

It naturally explains the timing of cosmic acceleration and impending collapse.

Abstract

Recently we proposed a mechanism for sequestering the Standard Model vacuum energy that predicts that the universe will collapse. Here we present a simple mechanism for bringing about this collapse, employing a scalar field whose potential is linear and becomes negative, providing the negative energy density required to end the expansion. The slope of the potential is chosen to allow for the expansion to last until the current Hubble time, about $10^{10}$ years, to accommodate our universe. Crucially, this choice is technically natural due to a shift symmetry. Moreover, vacuum energy sequestering selects {\it radiatively stable} initial conditions for the collapse, which guarantee that immediately before the turnaround the universe is dominated by the linear potential which drives an epoch of accelerated expansion for at least an efold. Thus a single, technically natural choice for the slope ensures that the collapse is imminent and is preceded by the current stage of cosmic acceleration, giving a new answer to the 'Why Now?' problem.