Void magnetic field and its primordial origin in inflation

Since magnetic fields in galaxies, galactic clusters and even void regions are observed, theoretical attempts to explain their origin are strongly motivated. It is interesting to consider that inflation is responsible for the origin of the magnetic fields as well as the density perturbation. However, it is known that inflationary magnetogenesis suffers from several problems. We explore these problems by using a specific model, namely the kinetic coupling model, and show how the model is constrained. Model independent arguments are also discussed.