Gravitational memory effects and Bondi-Metzner-Sachs symmetries in scalar-tensor theories

Understand

The relation between gravitational memory effects and Bondi-Metzner-Sachs symmetry of the asymptotically flat spacetimes is studied in the scalar-tensor theory.

• For this purpose, the solutions to the equations of motion near the future null infinity are obtained in the generalized Bondi-Sachs coordinates with a suitable determinant condition.
• It turns out that the Bondi-Metzner-Sachs group is also a semi-direct product of an infinitesimal dimensional supertranslation group and the Lorentz group as in general relativity.
• There are also degenerate vacua in both the tensor and the scalar sectors in the scalar-tensor theory.