Stars disformally coupled to a shift-symmetric scalar field

Understand

We investigate static and spherically symmetric stars disformally coupled to a scalar field.

• The scalar field is assumed to be shift symmetric, and hence the conformal and disformal factors of the metric coupled to matter are dependent only on the kinetic term of the scalar field.
• Assuming that the scalar field is linearly dependent on time, we consider a general shift-symmetric scalar-tensor theory and a general form of the matter energy-momentum tensor that allows for the anisotropic pressure and the heat flux in the radial direction.
• This is a natural starting point in light of how the gravitational field equations and the energy-momentum tensor transform under a disformal transformation.