Dark Energy in Practice

TL;DR

This review discusses dark energy and alternative gravity theories explaining the universe's late-time acceleration, highlighting observational challenges and future experiments to distinguish between these models.

Contribution

It provides a comparative analysis of dark energy and modified gravity theories, emphasizing the need for measurable parameters in future cosmological studies.

Findings

Dark energy is the leading explanation for cosmic acceleration.

Current observations cannot definitively distinguish between dark energy and modified gravity.

Future experiments are crucial for understanding the universe's acceleration mechanisms.

Abstract

In this paper we review a part of the approaches that have been considered to explain the extraordinary discovery of the late time acceleration of the Universe. We discuss the arguments that have led physicists and astronomers to accept dark energy as the current preferable candidate to explain the acceleration. We highlight the problems and the attempts to overcome the difficulties related to such a component. We also consider alternative theories capable of explaining the acceleration of the Universe, such as modification of gravity. We compare the two approaches and point out the observational consequences, reaching the sad but foresightful conclusion that we will not be able to distinguish between a Universe filled by dark energy or a Universe where gravity is different from General Relativity. We review the present observations and discuss the future experiments that will help us to learn more about our Universe. This is not intended to be a complete list of all the dark energy models but this paper should be seen as a review on the phenomena responsible for the acceleration. Moreover, in a landscape of hardly compelling theories, it is an important task to build simple measurable parameters useful for future experiments that will help us to understand more about the evolution of the Universe.