Cosmic acceleration and the challenge of modifying gravity

TL;DR

This paper discusses the difficulties and constraints in modifying general relativity to explain cosmic acceleration, emphasizing theoretical consistency and observational tests, and explores higher-dimensional gravity models as a potential approach.

Contribution

It reviews the challenges of constructing consistent modified gravity models and introduces a recent approach using higher-dimensional induced gravity for cosmological insights.

Findings

Modified gravity models face ghost and solar system constraints.

Upcoming observational data can potentially rule out or support these models.

Higher-dimensional induced gravity offers a promising avenue for cosmological modeling.

Abstract

I briefly discuss the challenges presented by attempting to modify general relativity to obtain an explanation for the observed accelerated expansion of the universe. Foremost among these are the questions of theoretical consistency - the avoidance of ghosts in particular - and the constraints imposed by precision local tests of gravity within the solar system. For those models that clear these highly constraining hurdles, modern observational cosmology offers its own suite of tests, improving with upcoming datasets, that offer the possibility of ruling out modified gravity approaches or providing an intriguing hint of new infrared physics. In the second half of the talk, I discuss a recent approach to extracting cosmology from higher-dimensional induced gravity models.