Cosmological backgrounds of gravitational waves

By C. Caprini, Daniel G. Figueroa. Classical and quantum gravity, 2018

946 citations recorded by the source corpus.

Gravitational waves (GWs) have a great potential to probe cosmology. We review early universe sources that can lead to cosmological backgrounds of GWs. We begin by presenting proper definitions of GWs in flat space-time and in a cosmological setting (section ). Following, we discuss the reasons why early universe GW backgrounds are of a stochastic nature, and describe the general properties of a stochastic background (section ). We recap current observational constraints on stochastic backgrounds, and discuss the basic characteristics of present and future GW detectors, including advanced LIGO, advanced Virgo, the Einstein telescope, KAGRA, and LISA (section ). We then review in detail early universe GW generation mechanisms, as well as the properties of the GW backgrounds they give rise to. We classify the backgrounds in five categories: GWs from quantum vacuum fluctuations during standard slow-roll inflation (section ), GWs from processes that operate within extensions of the standard inflationary paradigm (section ), GWs from post-inflationary preheating and related non-perturbative phenomena (section ), GWs from first order phase transitions related or not to the electroweak symmetry breaking (section ), and GWs from general topological defects, and from cosmic strings in particular (section ). The phenomenology of these early universe processes is extremely rich, and some of the GW backgrounds they generate can be within the reach of near-future GW detectors. A future detection of any of these backgrounds will provide crucial information on the underlying high energy theory describing the early universe, probing energy scales well beyond the reach of particle accelerators.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/fc9add2f4d2c2f3c1b6d6c3304e76f116f9e2fea

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Citations in the corpus

Gravitational waves induced by scalar perturbations during a gradual transition from an early matter era to the radiation era (2019, neutral): “[7] for a recent review and Ref.”
Science case for the Einstein telescope (2019, background): “um vacuum uctuations due to the in ationary expansion is expected to be too low to be detected by 3G detectors, there are several other in ation-related mechanisms that can produce detectable signals [82,122,123]. For example, large GW amplitudes are naturally produced in in ationary models where th”
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Gravitational wave constraints on the primordial black hole dominated early universe (2020, background): “4The constraint on the energy density ratio of gravitational waves at the time of BBN is [75]”
Oscillations in the stochastic gravitational wave background from sharp features and particle production during inflation (2020, background): “Cosmological contributions to the SGWB arise from phase transitions, topological defects, tensor fluctuations sourced during inflation or preheating, and GWs induced by primordial scalar fluctuations in the post-inflationary era, see [2, 3] for recent reviews of these topics.”
Unveiling the gravitational universe at μ-Hz frequencies (2019, background): “to the Hubble factor at generation time H∗ [63]”
Dark Energy in Light of Multi-Messenger Gravitational-Wave Astronomy (2018, background): “For a nice review in the subject one can follow (Caprini and Figueroa, 2018).”