Signatures of extra dimensions in gravitational waves

Understand

Considering gravitational waves propagating on the most general 4+N-dimensional space-time, we investigate the effects due to the N extra dimensions on the four-dimensional waves.

• All wave equations are derived in general and discussed.
• On Minkowski4 times an arbitrary Ricci-flat compact manifold, we find: a massless wave with an additional polarization, the breathing mode, and extra waves with high frequencies fixed by Kaluza-Klein masses.
• We discuss whether these two effects could be observed.