Braneworld Cosmological Perturbations in Teleparallel Gravity

TL;DR

This paper develops gauge-invariant cosmological perturbation equations within braneworld teleparallel gravity, highlighting differences from general relativity, especially in tensor mode origins from the contortion tensor.

Contribution

It introduces a fully gauge-invariant framework for cosmological perturbations in braneworld teleparallel gravity, emphasizing the role of pentad fluctuations and contortion tensor in tensor modes.

Findings

Perturbations originate from pentad field fluctuations.

Tensor modes are derived from the contortion tensor.

Scalar and vector modes are present, tensor modes differ from GR.

Abstract

We describe the fully gauge invariant cosmological perturbation equations in braneworld teleparallel gravity. In this theory, perturbations are the result of small fluctuations in the pentad field. We derive the gauge invariant 'potentials' for both geometric and matter variables. Unlike the metric fluctuations in general relativity, pentad perturbations can only contain scalar and vector modes. As a result, in teleparallel gravity, tensor modes including gravitational waves, come from the contortion tensor.