Spin-2 dark matter from an anisotropic universe in bigravity
Yusuke Manita, Katsuki Aoki, Tomohiro Fujita, Shinji Mukohyama
Abstract
Bigravity is one of the natural extensions of general relativity and contains an additional massive spin-2 field which can be a good candidate for dark matter. To discuss the production of spin-2 dark matter, we study fixed-point solutions of the background equations for axisymmetric Bianchi type-I universes in two bigravity theories without a Boulware-Deser ghost, i.e., Hassan-Rosen bigravity and the minimal theory of bigravity. We investigate the local and global stabilities of the fixed points and classify them. Based on the general analysis, we propose a new scenario where spin-2 dark matter is produced by the transition from an anisotropic fixed-point solution to an isotropic one. The produced spin-2 dark matter can account for all or a part of dark matter and can be directly detected by laser interferometers in the same way as gravitational waves.