Gravitational-wave cosmology across 29 decades in frequency

By P. Lasky, C. Mingarelli, Tristan L. Smith, John T. Giblin Jr., E. Thrane, D. Reardon, Robert R. Caldwell, M. Bailes, N. Bhat, S. Burke-Spolaor and 18 more. 2015

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Quantum fluctuations of the gravitational field in the early Universe, amplified by inflation, produce a primordial gravitational-wave background across a broad frequency band. We derive constraints on the spectrum of this gravitational radiation, and hence on theories of the early Universe, by combining experiments that cover 29 orders of magnitude in frequency. These include Planck observations of cosmic microwave background temperature and polarization power spectra and lensing, together with baryon acoustic oscillations and big bang nucleosynthesis measurements, as well as new pulsar timing array and ground-based interferometer limits. While individual experiments constrain the gravitational-wave energy density in specific frequency bands, the combination of experiments allows us to constrain cosmological parameters, including the inflationary spectral index n_t and the tensor-to-scalar ratio r. Results from individual experiments include the most stringent nanohertz limit of the primordial background to date from the Parkes Pulsar Timing Array, Ω_(GW)(f) < 2.3 × 10^(−10). Observations of the cosmic microwave background alone limit the gravitational-wave spectral index at 95% confidence to n_t ≲ 5 for a tensor-to-scalar ratio of r = 0.11. However, the combination of all the above experiments limits n_t < 0.36. Future Advanced LIGO observations are expected to further constrain n_t < 0.34 by 2020. When cosmic microwave background experiments detect a nonzero r, our results will imply even more stringent constraints on n_t and, hence, theories of the early Universe.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7506bbcd95742c6ddb75a9e367c5a4430ee3a704

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Citations in the corpus

New physics from the polarized light of the cosmic microwave background (2022, background): “The most important message of this figure is that the GW spectrum spans a huge range of f , and various experiments can measure them across at least 21 decades in f 164–168 .”
Science with the space-based interferometer LISA. IV: probing inflation with gravitational waves (2016, background): “02 [79], even in the case of a detection of B-modes.”
The NANOGrav 11-year Data Set: High-precision Timing of 45 Millisecond Pulsars (2017, background): “…et al. 2014; Arzoumanian et al. 2015a), primordial gravitational waves from inflation (Grishchuk 1976, 1977; Starobinsky 1980; Lentati et al. 2015; Lasky et al. 2016), and gravitational waves originating from cosmic strings (e.g., Kibble 1976; Vilenkin 1981; Sanidas et al. 2012; Arzoumanian et…”
The NANOGrav 11 Year Data Set: Pulsar-timing Constraints on the Stochastic Gravitational-wave Background (2018, background): “…sources of cosmological origin, such as cosmic strings (Damour & Vilenkin 2001; Ölmez et al. 2010) and/or a primordial GW background (GWB) produced by quantum fluctuations of the gravitational field in the early Universe, amplified by inflation, e.g. Grishchuk (2005); Lasky et al. (2016).”
Primordial gravitational waves from axion-gauge fields dynamics (2016, background): “It is important to stress that, even if the amplitude of B-modes will turn out to be below the sensitivity threshold of upcoming experiments, these will provide bounds severely restricting the viable parameter space for inflationary models [62].”