Polarization of a stochastic gravitational wave background through diffusion by massive structures

Understand

The geometric optics approximation traditionally used to study the propagation of gravitational waves on a curved background, breaks down in the vicinity of compact and extended astrophysical objects, where wave-like effects like diffusion and generation of polarization occur.

• We provide a framework to study the generation of polarization of a stochastic background of gravitational waves propagating in an inhomogeneous universe.
• The framework is general and can be applied to both cosmological and astrophysical gravitational wave backgrounds in any frequency range.
• We derive an order of magnitude estimate of the amount of polarization generated for cosmological and astrophysical backgrounds, in the frequency range covered by present and planned gravitational wave experiments.