Constraints on CPT violation from WMAP three year polarization data: a wavelet analysis

We perform a wavelet analysis of the temperature and polariz ation maps of the Cosmic Microwave Background (CMB) delivered by the WMAP experiment in search for a parity violating signal. Such a signal could be seeded by new physics beyond the standard mo del, for which the Lorentz and CPT symmetries may not hold. Under these circumstances, the lin ear polarization direction of a CMB photon may get rotated during its cosmological journey, a ph enomenon also called cosmological birefringence. Recently, Feng et al. have analyzed a subset the WMAP and BOOMERanG 2003 angular power spectra of the CMB, deriving a constraint that mildly favors a non zero rotation. By using wavelet transforms we set a tighter limit on the CMB pho ton rotation angle ∆ alpha = − 2 . 5 ± 3 . 0 (∆ alpha = − 2 . 5 ± 6 . 0) at the one (two) sigma level, consistent with a null detection