Probe of spatial geometry from scalar induced gravitational waves

Understand

We investigate a novel probe of spatial geometry of the Universe through the observation of gravitational waves (GWs) induced by first order curvature perturbations.

• The existence of spatial curvature leaves imprints on the gravitational wave spectrum and formation of primordial black holes.
• Given the peaked scalar spectrum, the induced spectrum deviates from the flat space power spectrum and the deviation is dependent on the spatial curvature K and reheating temperature $T_{rh}$.
• For prolonged reheating and negative spatial curvature the spectrum is amplified enough and exhibits an additional peak solely due to K indicating a possible detection by future gravitational wave experiments including LISA and DECIGO.