title: Inflationary universe with anisotropic hair.
abstract: We study an inflationary scenario with a vector field coupled with an inflaton field and show that the inflationary Universe is endowed with anisotropy for a wide range of coupling functions. This anisotropic inflation is a tracking solution where the energy density of the vector field follows that of the inflaton field irrespective of initial conditions. We find a universal relation between the anisotropy and a slow-roll parameter of inflation. Our finding has observational implications and gives a counterexample to the cosmic no-hair conjecture.
authors.affiliation: Department of Physics, Kyoto University, Kyoto, 606-8501, Japan.
authors.forename: Masa-Aki
authors.initials: MA
authors.lastname: Watanabe
authors.forename: Sugumi
authors.initials: S
authors.lastname: Kanno
authors.forename: Jiro
authors.initials: J
authors.lastname: Soda