Abstract: Among the various modified theories of gravity, scalar-tensor theories are arguablythe most natural extensions to general relativity. Particularly interesting classesof these theories satisfy the stringent experimental constraints imposed in theweak-field limit, yet can largely deviate in their predictions from general relativityin the strong-field regime in presence of matter such as in neutron stars. This occursthrough a mechanism called spontaneous scalarization, where a non-trivial scalar fieldcan exist within the star altering its properties. Such scalar-tensor theories typicallyinvolve a conformal coupling between scalar field and matter. More recentlyhowever, it was understood that scalar-tensor theories allow for a wider class ofcouplings, named disformal. In this presentation we introduce the ideas of spontaneousscalarization and disformal coupling, discussing their impact on the structure ofneutron stars in scalar-tensor theories of gravity.
This seminar is supported by Portuguese Funds through the CIDMA - Centre for Research and Development in Mathematics and Applications, and the Portuguese Foundation for Science and Technology ("FCT" - Fundação para a Ciência e a Tecnologia), within the project UID/MAT/04106/2013.