Scalarization of dark matter stars

Abstract: We investigated scalarization in dark matter stars. In scalar tensor theories, the coupling between matter and a scalar field generates an effective mass, which is known to trigger the growth of the scalar field in stars and black holes (spontaneous scalarization). On the other hand, models in which the scalar field couples not only to baryonic matter but also to dark matter have been discussed in the literature. Moreover, in models with self interacting dark matter, it is known that dark matter can form compact objects. Within the framework of scalar tensor theories, we studied the parameter ranges in which the growth of the scalar field occurs in compact stars formed by self interacting dark matter. As a result, we found that scalarization occurs over most of the parameter region with a negative coupling parameter $β_d$. This parameter range is broader than that for scalarization in conventional neutron stars. Since the dark matter parameters considered correspond to those in which self-interacting dark matter resolves problems in galaxy formation, if dark matter stars actually exist, they could serve as probes for investigating the relationship between the scalar field and dark matter.