Eddington-Born-Infeld gravity and the large scale structure of the Universe

TL;DR

This paper explores Eddington-Born-Infeld gravity as a unified framework for dark matter and dark energy, analyzing its effects on cosmic expansion and structure formation, and identifying conditions for compatibility with observations.

Contribution

It demonstrates how extra fields in Eddington-Born-Infeld gravity can mimic dark matter and dark energy, and examines their impact on large-scale structure and cosmic microwave background fluctuations.

Findings

Extra fields can behave as non-particulate dark matter with a cosmological constant.

Without a cosmological constant, the theory predicts excessive CMB fluctuations.

With a cosmological constant, the model aligns with current large-scale structure observations.

Abstract

It has been argued that a Universe governed by Eddington-Born-Infeld gravity can be compatible with current cosmological constraints. The extra fields introduced in this theory can behave both as dark matter and dark energy, unifying the dark sector in one coherent framework. We show the various roles the extra fields can play in the expansion of the Universe and study the evolution of linear perturbations in the various regimes. We find that, as a unified theory of the dark sector, Eddington-Born-Infeld gravity will lead to excessive fluctuations in the Cosmic Microwave Background on large scales. In the presence of a cosmological constant, however, the extra fields can behave as a form of non-particulate dark matter and can lead to a cosmology which is entirely compatible with current observations of large scale structure. We discuss the interpretation of this form of dark matter and how it can differ from standard, particulate dark matter.