Well-tempered Minkowski solutions in teleparallel Horndeski theory. (8th December 2021)

• Record Type: Journal Article
• Authors: Bernardo, Reginald Christian; Levi Said, Jackson; Caruana, Maria; Appleby, Stephen
• Is Part Of: Classical and quantum gravity. Volume 39:Number 1(2022)
• Publication Date: 2021-12-08
• Subjects: Minkowski vacuum state -- self-tuning solution -- well-tempered cosmology -- teleparallel gravity -- scalar-tensor theory -- vacuum energy; Quantum gravity -- Periodicals; Gravitation -- Periodicals; Relativity (Physics) -- Periodicals; Space and time -- Periodicals; Periodicals; 521.1
• DOI: 10.1088/1361-6382/ac36e4
• Languages: English
• ISSNs: 0264-9381

Abstract

Abstract: Well-tempering stands among the few classical methods of screening vacuum energy to deliver a late-time, low energy vacuum state. We build on the class of Horndeski models that admit a Minkowski vacuum state despite the presence of an arbitrarily large vacuum energy to obtain a much larger family of models in teleparallel Horndeski theory. We set up the routine for obtaining these models and present a variety of cases, all of which are able to screen a natural particle physics scale vacuum energy using degeneracy in the field equations. We establish that well-tempering is the unique method of utilizing degeneracy in Horndeski scalar-tensor gravity—and its teleparallel generalisation—that can accommodate self-tuned flat Minkowski solutions, when the explicit scalar field dependence in the action is minimal (a tadpole and a conformal coupling to the Ricci scalar). Finally, we study the dynamics of the well-tempered teleparallel Galileon. We generate its phase portraits and assess the attractor nature of the Minkowski vacuum under linear perturbations and through a phase transition of vacuum energy. 'The effort to understand the Universe is one of the very few things that lifts human life a little above the level of farce, and gives it some of the grace of tragedy.' -Steven Weinberg