Well-Tempered Minkowski Solutions in Teleparallel Horndeski Theory

Understand

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).