Electromagnetic wave propagation in general Kasner-like metrics

The curved spacetime Maxwell equations are applied to the anisotropically expanding Kasner metrics. Using application of vector identities we derive second-order differential wave for electromagnetic field components; through this explicit derivation, find that not uncoupled various components (as previously assumed), but gravitationally induced coupling between electric and magnetic is generated directly by anisotropy expansion. lack such terms in from several prior studies may indicate a generally incomplete understanding evolution energy anisotropic cosmologies. Uncoupling requires derivation fourth-order equation, which obtain Kasner-like metrics with generalized expansion/contraction rate indices. For axisymmetric case, [Formula: see text], exact solutions (for general propagation vectors), half appear have been found before previous studies. other use numerical methods demonstrate violation geometric optics approximation at early times, showing physical phase velocity be inhibited towards initial singularity, text] as text].