Why scalar field is indispensable in Teleparallel Gravity theory?

TL;DR

This paper discusses the importance of scalar fields in teleparallel gravity theories, highlighting their role in driving early inflation and radiation eras despite issues in other formulations.

Contribution

It emphasizes the necessity of scalar fields in teleparallel gravity to achieve viable cosmological evolution, addressing limitations of other formulations.

Findings

Scalar fields are essential for early inflation.

Scalar fields enable a viable radiation era.

Teleparallel theories are free from branched Hamiltonian issues.

Abstract

Teleparallel gravity theories were proposed as alternatives to the dark energy and modified theories of gravity. However, both the metric and symmetric teleparallel gravity theories have been found to have serious pathologies, such as coupling issues and Ostrogradski's instability leading to ghost degrees of freedom. In this article we explore the fact that the theories are at-least free from the issue of `Branched Hamiltonian' though, nonetheless, early inflation as well as a viable radiation era may only be driven by a scalar field.