Induced gravitational waves: the effect of first order tensor perturbations

Understand

Scalar induced gravitational waves contribute to the cosmological gravitational wave background.

• They can be related to the primordial density power spectrum produced towards the end of inflation and therefore are a convenient new tool to constrain models of inflation.
• These waves are sourced by terms quadratic in perturbations and hence appear at second order in cosmological perturbation theory.
• While the focus of research so far was on purely scalar source terms we also study the effect of including first order tensor perturbations as an additional source.