Parity-violating Kalb-Ramond-Maxwell interactions and CMB anisotropy in a braneworld

TL;DR

This paper explores how string-inspired parity-violating interactions in a braneworld scenario could produce observable effects in CMB anisotropies, highlighting the need for further investigation into string-braneworld connections.

Contribution

It demonstrates potential enhancements in CMB parity-violating correlations due to string-based Kalb-Ramond axion-photon interactions within a Randall-Sundrum braneworld.

Findings

Potential observable parity-violating correlations in CMB anisotropy.

Non-observation would imply unnatural fine tuning of parameters.

Highlights the need to connect string models with braneworld scenarios.

Abstract

Following up on a recent paper by two of us (DM and SS), demonstrating the large enhancement in observable optical activity in radiation from high redshift sources arising from the string-based coupling of bulk Kalb-Ramond field to the Maxwell Chern Simons three-form on the brane in a Randall-Sundrum braneworld, we exhibit here a similar enhancement in parity-violating temperature-polarization correlations, yet unseen, in the CMB anisotropy due to a generalized parity-violating Kalb-Ramond axion-photon interaction proposed earlier by one of us (PM). The non-observation of such correlations in CMB anisotropies would necessitate unnatural fine tuning of the Kalb-Ramond axion parameters. As a stringy realization of Randall-Sundrum braneworld scenario is yet to be understood properly, our work indicates the need of a careful investigation to establish the connection between string-based phenomenological models and the Randall-Sundrum braneworld scenario