Factorization and polarization in linearized gravity.

We investigate all the four-body graviton interaction processes: gX → γX, gX → gX, and gg → gg with X as an elementary particle of spin less than two in the context of linearized gravity except the spin-3/2 case. We show explicitly that gravitational gauge invariance and Lorentz invariance cause every four-body graviton scattering amplitude to be factorized. We explore the implications of this factorization property by investigating polarization effects through the covariant density matrix formalism in each four-body graviton scattering process. PACS number(s) : 04.60.+n, 12.25.+e, 13.88.+e