Well-tempered teleparallel Horndeski cosmology: a teleparallel variation to the cosmological constant problem

TL;DR

This paper extends well-tempered cosmology to teleparallel Horndeski gravity, demonstrating its potential to address the cosmological constant problem through stable, dynamically screened vacuum states compatible with matter eras.

Contribution

It introduces the first self-tuning, well-tempered cosmological models within teleparallel Horndeski gravity, broadening the scope of dynamical screening mechanisms.

Findings

Demonstrated the stability of the vacuum in teleparallel well-tempered models

Showed compatibility with matter-dominated eras

Established stability through phase transitions

Abstract

Well-tempering is a promising classical method of dynamically screening an arbitrarily large vacuum energy and generating a late-time, low energy de Sitter vacuum state. In this paper, we study for the first time self-tuning in teleparallel gravity and obtain well-tempered cosmological models in the teleparallel gravity analogue of Horndeski theory. This broadens the scope of well-tempered cosmology and teases the potentially far richer cosmological dynamics that could be anchored on teleperallel gravity. We expand the well-tempered recipe to its most general form so far and use it to search for the first well-tempered cosmologies in teleparallel gravity. We also study the cosmological dynamics in a well-tempered model and demonstrate the dynamical stability of the vacuum, the compatibility with a matter era, and the stability of the vacuum through a phase transition.