Gravitational Wave Spectrums from Pole-like Inflations based on Generalized Gravity Theories

TL;DR

This paper develops a unified framework for analyzing gravitational wave spectra generated during pole-like inflation in various generalized gravity theories, deriving analytic power spectra and comparing them to observational data.

Contribution

It introduces a comprehensive formulation for gravitational wave evolution in generalized gravity theories and derives analytic spectra for pole-like inflation models, highlighting differences from standard inflation.

Findings

Derived analytic gravitational wave power spectra for pole-like inflation

Identified distinctive features in spectra from generalized gravity theories

Compared spectra with observational data, noting deviations from scale invariance

Abstract

We present a general and unified formulation which can handle the classical evolution and quantum generation processes of the cosmological gravitational wave in a broad class of generalized gravity theories. Applications are made in several inflation models based on the scalar-tensor theory, the induced gravity, and the low energy effective action of string theory. The gravitational wave power spectrums based on the vacuum expectation value of the quantized fluctuating metric during the pole-like inflation stages are derived in analytic forms. Assuming that the gravity theory transits to Einstein one while the relevant scales remain in the superhorizon scale, we derive the consequent power spectrums and the directional fluctuations of the relic radiation produced by the gravitational wave. The spectrums seeded by the vacuum fluctuations in the pole-like inflation models based on the generalized gravity show a distinguished common feature which differs from the scale invariant spectrum generated in an exponential inflation in Einstein gravity which is supported by observations.