We show that the Cosmic Microwave Background (CMB) polarization data gathered by the BOOMERanG 2003 flight and WMAP provide an opportunity to investigate {\it in-vacuo} birefringence, of a type expected in some quantum pictures of space-time, with a sensitivity that extends even beyond the desired Planck-scale energy. In order to render this constraint more transparent we rely on a well studied phenomenological model of quantum-gravity-induced birefringence, in which one easily establishes that effects introduced at the Planck scale would amount to values of a dimensionless parameter, denoted by ξ, with respect to the Planck energy which are roughly of order 1. By combining BOOMERanG and WMAP data we estimate ξ≃−0.110±0.076 at the 68% c.l. Moreover, we forecast on the sensitivity to ξ achievable by future CMB polarization experiments (PLANCK, Spider, EPIC), which, in the absence of systematics, will be at the 1-σ confidence of 8.5×10−4 (PLANCK), 6.1×10−3 (Spider), and 1.0×10−5 (EPIC) respectively. The cosmic variance-limited sensitivity from CMB is 6.1×10−6.
@article{arxiv.0904.3201,
title = {A Constraint on Planck-scale Modifications to Electrodynamics with CMB polarization data},
author = {Giulia Gubitosi and Luca Pagano and Giovanni Amelino-Camelia and Alessandro Melchiorri and Asantha Cooray},
journal= {arXiv preprint arXiv:0904.3201},
year = {2009}
}