Stochastic Gravitational Wave Backgrounds from Low-Scale Inflation

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Nerval, Simran
Inflation , Gravitational Waves , Early Universe Cosmology , Phenomenology
While Big Bang cosmology successfully explains much of the history of our Universe, there are certain features it does not explain, for example the spatial flatness and uniformity of our Universe. One widely studied explanation for these features is cosmological inflation. The objective of this thesis was to simulate the gravitational wave spectra generated by inflaton field configurations oscillating after inflation for E-Model, T-Model, and General Renormalizable Inflection Point Inflation. This thesis shows that these gravitational wave spectra provide access to some inflation models beyond the reach of any planned Cosmic Microwave Background (CMB) experiments, such as LiteBIRD, Simons Observatory, and CMB-S4. Specifically, while these experiments will be able to resolve the primordial power spectrum tensor-to-scalar ratio (r) down to 10^(-3), we show that gravitational wave background measurements have the potential to probe certain inflation models for r values down to 10^(-14). Importantly, all the gravitational wave spectra lie in the MHz-GHz frequency range, motivating development of gravitational wave detectors in this range.
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