Issue of Branched Hamiltonian, Inflation and indispensability of scalar field in generalized Teleparallel theories

Abstract

Generalized Teleparallel gravity theories were proposed as alternatives to the dark energy and modified theories of gravity. However, minimal generalization of TEGR and STEGR lead to the issue of branched Hamiltonian. Here, in the FLRW background we fix the coupling parameters of the said model in view of energy condition and show that the theory is free from the issue of Branched Hamiltonian unlike second-order Lanczos-Lovelock gravity. We also study scalar field driven inflation, which shows excellent agreement with recent observations. Nonetheless, a viable radiation era requires the very presence of the scalar field, which is retained at the late universe as dark energy. Thus the fundamental claim to act as an alternative to the dark energy is dubious.