Cosmological redshift and nonlinear electrodynamics propagation of photons from distant sources

By-now photons are the unique universal messengers. Cosmological sources like far-away galaxies or quasars are well-known light-emitters. Here we demonstrate that the nonlinear electrodynamics (NLED) description of photon propagation through the weak background intergalactic magnetic fields modifies in a fundamental way the cosmological redshift that a direct computation within a specific cosmological model can abscribe to a distant source. Independently of the class of NLED Lagrangian, the effective redshift turns out to be $1 + \tilde{z} = (1 + z) \Delta$,where$\Delta \equiv (1 + \Phi_e)/(1 + \Phi_o)$, with $\mathrm{\Phi }\equiv 8\mathrm{/}3(L_{FF}\mathrm{/}{L}_F)B^2$, being $L_F=dL\mathrm{/}dF$, $L_{FF}=d^{2}L\mathrm{/}d{F}^2$, the field $F\equiv F_{\alpha \beta} F^{\alpha \beta}$,and$B$ the magnetic field strength. Thus the effective redshift is always much higher then the standard redshift, but recovers such limit when the NLED correction $\mathrm{\Delta }({\mathrm{\Phi }}_e,{\mathrm{\Phi }}_o)⟶1$. This result may provide a physical foundation for the current observation-inspired interpretation that the universe undergoes an accelerate expansion. However, under the situation analyzed here, for any NLED the actual (spatial) position of the light-emitting far-away source remains untouched.