SPEAKER: Hector O. Silva (Mississippi University)
ABSTRACT: Among the various modified theories of gravity, scalar-tensor theories are arguably the most natural extensions to general relativity. Particularly interesting classes of these theories satisfy the stringent experimental constraints imposed in the weak-field limit, yet can largely deviate in their predictions from general relativity in the strong-field regime in presence of matter such as in neutron stars. This occurs through a mechanism called spontaneous scalarization, where a non-trivial scalar field can exist within the star altering its properties. Such scalar-tensor theories typically involve a conformal coupling between scalar field and matter. More recently however, it was understood that scalar-tensor theories allow for a wider class of couplings, named disformal. In this presentation we introduce the ideas of spontaneous scalarization and disformal coupling, discussing their impact on the structure of neutron stars in scalar-tensor theories of gravity.