Some Adventures in the Search for a Modified Gravity Explanation for Cosmic Acceleration

TL;DR

This paper reviews various modified gravity theories, including f(R), DGP, and Galileon models, as potential explanations for cosmic acceleration, aiming to find a consistent and observationally viable alternative to dark energy.

Contribution

It provides a comprehensive overview of recent theoretical developments in modified gravity models addressing cosmic acceleration, including new extensions of Galileon theories.

Findings

f(R) models and DGP can produce accelerated expansion

Galileon models offer effective field theory descriptions of extra-dimensional effects

Recent multifield and curved space extensions enhance model viability

Abstract

The discovery of cosmic acceleration has raised the intriguing possibility that we are witnessing the first breakdown of General Relativity on cosmological scales. In this article I will briefly review current attempts to construct a theoretically consistent and observationally viable modification of gravity that is capable of describing the accelerating universe. I will discuss f(R) models, and their obvious extensions, and the DGP model as an example of extra-dimensional implementations. I will then briefly describe the Galileon models and their very recent multifield and curved space extensions - a class of four-dimensional effective field theories encoding extra dimensional modifications to gravity. This article is dedicated to the career of my friend and former colleague, Joshua Goldberg, and is written to appear in his festschrift.