Speaker
Description
The interaction of gravitational waves (GWs) passing through matter is normally treated as being very weak. We have re-investigated this issue using linearized perturbations within the Bondi-Sachs formalism, with a model comprising a spherical shell of matter surrounding a GW source. We find analytic expressions for the GWs when the background is Minkowskian, but for a general spherically symmetric background the GWs are found numerically. If the matter in the shell has high viscosity, then the shear induced in the velocity field results in an energy transfer so damping the GWs and heating the matter. The effect is very weak when the matter is far from the GW source, but can be highly significant when the shell radius is less than the GW wavelength. The applications to astrophysics include supernova explosions, the quasinormal mode regime after a neutron star merger, and a binary black hole merger at which matter is present, as well as to primordial gravitational waves in cosmology.