{'fraction_non_alphanumeric': 0.04717853839037928, 'fraction_numerical': 0.0, 'mean_word_length': 5.597560975609756, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Stochastic gravity-wave background in inflationary-universe models.

The gravitational-wave-noise power spectrum P(\ensuremath{\omega}) is found for a simple cosmological model with an ``inflationary'' early stage of expansion. The source of the gravitational-wave noise is quantum fluctuations during the inflationary de Sitter stage, which are amplified by the subsequent expansion of the Universe. The resulting spectrum P(\ensuremath{\omega}) is compared to a naive estimate: a thermal spectrum at the (appropriately red-shifted) Gibbons-Hawking temperature. The two spectra are remarkably different. Unlike the thermal spectrum, P(\ensuremath{\omega}) increases at low frequencies. We show that the source of the corresponding long-wavelength perturbations is a global gravitational instability during the inflationary de Sitter stage of expansion. An interesting consequence of the low-frequency behavior of P(\ensuremath{\omega}) is that gravitational radiation contributes a constant fraction of the energy density of the Universe, even after the time of matter domination.