Towards Strong Field Tests of Beyond Horndeski Gravity Theories

Understand

Theories of gravity in the beyond Horndeski class encompass a wide range of scalar-tensor theories that will be tested on cosmological scales over the coming decade.

• In this work, we investigate the possibility of testing them in the strong-field regime by looking at the properties of compact objects-neutron, hyperon, and quark stars-embedded in an asymptotically de Sitter space-time, for a specific subclass of theories.
• We extend previous works to include slow rotation and find a relation between the dimensionless moment of intertia, ($\bar{I}=Ic^2/G_{\rm N} M^3$), and the compactness, $\cal{C}=G_{\rm N} M/Rc^2$ (an $\bar{I}$-$\cal{C}$ relation), independent of the equation of state, that is reminiscent of but distinct from the general relativity prediction.
• Several of our equations of state contain hyperons and free quarks, allowing us to revisit the hyperon puzzle.