Photon mass and cosmological constant bounds from spacetime torsion

Photon mass and Cartan contortion bounds recently obtained from tiny Lorentz violation observations in cosmology are used to find a limit of ${\lambda}\le 10^{-4}{\alpha}$ for the massive photon-torsion dimensionless coupling. Here ${\alpha}$ represents the fine-structure constant. A gauge invariant Proca electrodynamics in spacetime endowed with torsion in de Sitter spacetime is used to obtain an upper bound for the present value of the cosmological constant given by ${\Lambda}\le 10^{-56} cm^{-2}$. This result is obtained in regions of the universe where the photons are massless. A relation between the contortion, photon mass and the radius of the universe is obtained. The Proca electrodynamics with torsion and the radius of the universe allow us to place more stringent bounds for the photon mass of $m_{\gamma}{\le} 10^{-44} GeV$ which is only two orders of magnitude lower than the astronomical bounds given by the PARTICLE DATA GROUP (PDG). We also show that charge is locally conserved in de Sitter spacetime with torsion and that plane waves are shown to be damping by contortion inhomogeneities while dispersion is isotropic and therefore Proca-Cartan photons do not violate Lorentz invariance.