Parity-violating Kalb–Ramond–Maxwell interactions andCMB anisotropy in a braneworld

Abstract

Following up on a recent paper by two of us (DM and SS),demonstrating the large enhancement in observable opticalactivity in radiation from high red-shift sources arising fromthe string-based coupling of bulk Kalb–Ramond field to theMaxwell–Chern–Simons three-form on the brane in aRandall–Sundrum braneworld, we exhibit here a similarenhancement in parity-violating temperature–polarizationcorrelations, as yet unseen, in the CMB anisotropy due to ageneralized parity-violating Kalb–Ramond axion–photoninteraction proposed earlier by one of us (PM). Thenon-observation of such correlations in CMB anisotropies wouldnecessitate unnatural fine tuning of the Kalb–Ramond axionparameters. As a stringy realization of the Randall–Sundrumbraneworld scenario is yet to be understood properly, our workindicates the need for a careful investigation to establish theconnection between string-based phenomenological models and theRandall–Sundrum braneworld scenario.