Large Anisotropies of the Stochastic Gravitational Wave Background from Cosmic Domain Walls

We investigate the stochastic gravitational wave background (SGWB) from cosmic domain walls (DWs) caused by quantum fluctuations of a light scalar field phi during inflation. Large-scale perturbations of phi lead to large-scale perturbations of DW energy density and anisotropies in the SGWB. We find that the angular power spectrum of this SGWB is scale invariant and at least of the order of 10(-2), which is a distinctive feature of observational interest. Since we have not detected primordial gravitational waves yet, anisotropies of the SGWB provide a nontrivial opportunity to verify the rationality of inflation and detect the energy scale of inflation, especially for low-scale inflationary models. Square kilometer array has the opportunity to detect the anisotropies of such SGWBs. The common-spectrum process observed recently by NANOGrav could also be interpreted by the SGWB from cosmic DWs.

Automated summary

The study focuses on the stochastic gravitational wave background (SGWB) generated by cosmic domain walls (DWs) due to quantum fluctuations of a light scalar field during inflation. The angular power spectrum of this SGWB is scale invariant and of observational interest, providing a unique opportunity to verify inflationary theories and detect inflation energy scales. Detecting the anisotropies of such SGWBs is possible with instruments like the Square Kilometer Array, and the common-spectrum process observed by NANOGrav could be linked to the SGWB from cosmic DWs.