A possible new cosmological redshift effect due to Λ on traveling gravitational waves in Friedmann universes

Abstract

In this paper, we continue the investigation concerning the propagation of gravitational waves in a cosmological background using Laplace transform. a We analyze the possible physical consequences of the result present in Ref. 19 where it is argued that a nonvanishing positive abscissa of convergence caused by the de Sitter expansion factor [Formula: see text] implies a shift in the frequencies domain of a traveling gravitational wave as measured by a comoving observer. In particular, we show that in a generic asymptotically de Sitter cosmological universe, this redshift effect does also arise. Conversely, in a universe expanding with, for example, a power law expansion, this phenomenon does not happen. This physically possible new redshift effect, although negligible for the actual very low value of [Formula: see text], can have interesting physical consequences concerning for example its relation with Bose–Einstein condensation or more speculatively with the nature of the cosmological constant in terms of gravitons, as recently suggested in Ref. 21 near a Bose–Einstein condensation phase.