A possible new cosmological redshift effect due to $\Lambda$ on traveling gravitational waves in Friedmann universes

TL;DR

This paper investigates a potential new redshift effect on gravitational waves caused by the cosmological constant in de Sitter universes, which could have implications for understanding dark energy and quantum gravity.

Contribution

It demonstrates that a frequency shift of gravitational waves occurs in asymptotically de Sitter universes due to the cosmological constant, a phenomenon absent in power-law expanding universes.

Findings

Redshift effect appears in de Sitter-like universes

No such effect in power-law expanding universes

Potential links to Bose-Einstein condensation and graviton properties

Abstract

In this paper we continue the investigation concerning the propagation of gravitational waves in a cosmological background using Laplace transform \cite{A}. We analyze the possible physical consequences of the result present in \cite{A} where it is argued that a non-vanishing positive abscissa of convergence caused by the de Sitter expansion factor $a(t)=e^{Ht}$ implies a shift in the frequencies domain of a traveling gravitational waves 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 $\Lambda$, 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 \cite{B} near a Bose-Einstein condensation phase.