Lorentz violation from torsion trace and non-minimal coupling in radio galactic dynamos

Abstract

Earlier Kostelecky et al. [A. Kostelecky, N. Russell, and J. Tasson, Phys Rev Lett 100, 111102 (2008).] have obtained torsion bounds from Lorentz violation, where torsion components are taken from the axial part of torsion. In this brief report it is shown that more stringent bounds may be obtained by using nearly minimal magnetogenesis torsion trace instead of the minimal coupling between photons and axial torsion used by Kostelecky and his group. Just for comparison, in Kostelecky et al., the most stringent limit is estimated to be ${10}^{\ensuremath{-}31}\text{ }\text{ }\mathrm{GeV}$ while here one obtains ${10}^{\ensuremath{-}33}\text{ }\text{ }\mathrm{GeV}$. This estimate is obtained by constraining the torsion to galactic astronomy data. From the point of view of magnetogenesis, an interesting physical consequence is that dynamo action is obtained when the torsion trace background is negative, while the magnetic field energy decays when torsion is positive. Polarization of radio-galaxies can be used to obtain an even more stringent limit of $T\ensuremath{\sim}1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}46}\text{ }\text{ }\mathrm{GeV}$ to Lorentz violation. Using WMAP, Kostelecky and Mewes [A. Kostelecky and M. Mewes, Astrophys. J. 689, L1 (2008)] have found limits of the order of ${10}^{\ensuremath{-}43}\text{ }\text{ }\mathrm{GeV}$. These results are obtained by making use of flat torsion modes [L. Garcia de Andrade, Phys Lett B 696, 1 (2011)], but may easily be extended to Riemann-Cartan spacetime.