Origin of Magnetic Fields in the Universe due to Nonminimal Gravitational-Electromagnetic Coupling

Basically the only existing theories for the creation of a magnetic field (B) in the Universe are the creation of a seed field $\sim {10}^{-20\mathrm{}}\mathrm{G}$ in spiral galaxy which is subsequently supposedly amplified up to the observed ${10}^{-6\mathrm{}}–{10}^{-5\mathrm{}}\mathrm{G}$ by a dynamo process or a seed intergalactic field of $\sim {10}^{-12\mathrm{}}–{10}^{-10\mathrm{}}\mathrm{G}$ which is amplified by collapse and differential rotation. No satisfactory dynamo theory, however, exists today. We show that a $\sim {10}^{-6\mathrm{}}–{10}^{-5\mathrm{}}\mathrm{G}$ magnetic field in spiral galaxies is directly obtained from a nonminimal gravitational-electromagnetic coupling, without the need of significant dynamo amplification.