Probing reheating temperature of the universe with gravitational wave background

TL;DR

This paper proposes that future gravitational wave observations around 1Hz can reveal the universe's thermal history before BBN, especially the reheating temperature, by analyzing the stochastic gravitational wave background.

Contribution

It demonstrates that space-based laser interferometers like DECIGO or BBO can determine the reheating temperature of the universe in the range of 10^{6-9} GeV, depending on specific parameters.

Findings

Detection of gravitational wave background can probe pre-BBN thermal history.

Reheating temperature can be estimated if it is around 10^{6-9} GeV.

Future experiments could constrain early universe models.

Abstract

Thermal history of the universe after big-bang nucleosynthesis (BBN) is well understood both theoretically and observationally, and recent cosmological observations also begin to reveal the inflationary dynamics. However, the epoch between inflation and BBN is scarcely known. In this paper we show that the detection of the stochastic gravitational wave background around 1Hz provides useful information about thermal history well before BBN. In particular, the reheating temperature of the universe may be determined by future space-based laser interferometer experiments such as DECIGO and/or BBO if it is around 10^{6-9} GeV, depending on the tensor-to-scalar ratio $r$ and dilution factor $F$.