Signatures of primordial gravitational waves in matter power spectrum
  We simulate the evolution of a dust universe from $z=1089$ to $z=0$ by
numerically integrating the Einstein's equation for a spatially flat
Friedmann-Lemaire-Robertson-Walker (FLRW) background spacetime with scalar
perturbations which are derived from the matter power spectrum produced with
the Code for Anisotropies in the Microwave Background (CAMB). To investigate
the effects of primordial gravitational waves (GWs) on the inhomogeneity of the
universe, we add an additional decaying, divergenceless and traceless
primordial tensor perturbation with its initial amplitude being $3\times
10^{-4}$ to the above metric. We find that this primordial tensor perturbation
suppresses the matter power spectrum by about $0.01\%$ at $z=0$ for modes with
wave number similar to its. This suppression may be a possible probe of a GWs
background in the future.
