Effective Lagrangians and Universality Classes of Nonlinear Bigravity

TL;DR

This paper introduces the concept of universality classes in nonlinear bigravity theories, exploring their physical origins and discussing formal and phenomenological aspects of multigravity models.

Contribution

It presents a fully non-linear formulation of multigravity and defines universality classes of effective Lagrangians for bigravity, highlighting their emergence in various physical contexts.

Findings

Non-linear multigravity theories naturally arise in brane configurations and Kaluza-Klein reductions.

The concept of universality classes helps categorize different effective Lagrangians.

Discussion of formal and phenomenological issues related to massive gravitons.

Abstract

We discuss the fully non-linear formulation of multigravity. The concept of universality classes of effective Lagrangians describing bigravity, which is the simplest form of multigravity, is introduced. We show that non-linear multigravity theories can naturally arise in several different physical contexts: brane configurations, certain Kaluza-Klein reductions and some non-commutative geometry models. The formal and phenomenological aspects of multigravity (including the problems linked to the linearized theory of massive gravitons) are briefly discussed.