Time-varying optical media, whose dielectric properties are actively modulated in time, introduce a host of novel effects the classical propagation light, and intense current interest. In quantum domain, time-dependent media can be used to convert vacuum fluctuations (virtual photons) into pairs real photons. We refer these processes broadly as ``dynamical effects'' (DVEs). Despite interest for...

Abstract We introduce consideration of dispersive aspects standard perfect fluid Friedmann cosmology and study the new qualitative behaviours cosmological solutions that emerge as parameter changes zero eigenvalues appear in linear part equations. find due to their insufficient degeneracy, Milne, flat, Einstein-static, de Sitter cannot properly bifurcate. However, versions Milne flat universes ...