Measuring the tilt of primordial gravitational-wave power spectrum from observations

Li, Jun; Chen, Zu-Cheng; Huang, Qing-Guo

doi:10.1007/s11433-019-9605-5

Cited by 30 publications

(11 citation statements)

References 39 publications

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“…Recently, four major pulsar timing array (PTA) collaborations, namely the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) [1,2], the Parkes PTA (PPTA) [3,4], the European PTA (EPTA) along with the Indian PTA (InPTA) [5,6], and the Chinese PTA (CPTA) [7], have jointly announced compelling evidence of a commonspectrum signal consistent with the Hellings-Downs spatial correlations [8] in their latest data sets, thus suggesting a gravitational wave (GW) origin for this signal. While various physical phenomena [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] can produce GW signals within the PTA frequency band, the precise origin of this signal, whether attributed to supermassive black hole binaries [24][25][26][27] or other cosmological sources , remains an ongoing subject of investigation.…”

Section: Introductionmentioning

confidence: 99%

Probing the equation of state of the early Universe with pulsar timing arrays

Liu,

Chen,

Huang

2023

J. Cosmol. Astropart. Phys.

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The recently released data by pulsar timing array (PTA) collaborations have amassed substantial evidence corroborating the existence of a stochastic signal consistent with a gravitational-wave background at frequencies around the nanohertz regime. We investigate the situation in which the PTA signal originates from scalar-induced gravitational waves (SIGWs), which serves as a valuable tool to probe the equation of state parameterwduring the Universe's early stages. The joint consideration of the PTA data from the NANOGrav 15-year data set, PPTA DR3, and EPTA DR2 yields thatw = 0.60+0.32-0.39(median + 90% credible interval), indicating a period of condensate domination at the production of SIGWs is allowed by the data. Moreover, the data also supports radiation domination (w = 1/3) within the 90% credible interval. We also impose an upper bound on the reheating temperature thatTrh ≲ 0.2 GeV and the constraint onwreveals valuable information on the inflationary potential and the dynamics at the end of inflation.

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Section: Introductionmentioning

confidence: 99%

Probing the equation of state of the early Universe with pulsar timing arrays

Liu,

Chen,

Huang

2023

J. Cosmol. Astropart. Phys.

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“…The predicted SGWB from compact binary coalescences is well modeled by a power law of slope n GW = 2/3, and n GW = 0 corresponds to a scale-invariant energy. For the primordial GWs, Ω GW (f ) ∝ f nt+αt ln(f /fCMB)/2 , where n t is the spectral index of primordial GW power spectrum and α t is the running of spectral index [60][61][62][63]. For the white noise which corresponds to a random signal, the spectral density S h is a constant, and then Ω GW (f ) ∝ f 3 .…”

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confidence: 99%

Log-dependent slope of scalar induced gravitational waves in the infrared regions

2020

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We analytically calculate the scalar induced gravitational waves (SIGWs) and find a log-dependent slope of SIGW in the infrared regions (f < fc), namely nGW(f ) = 3 − 2/ ln(fc/f ), and nGW(f ) = 2 − 2/ ln(fc/f ) near the peak if the power spectrum of scalar curvature perturbation is quite narrow, where fc is roughly the frequency at the peak of SIGW. Such a log-dependent slope can be taken as a new template for distinguishing SIGW from other sources.

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“…How to explain the flatness of our Universe is one of the crucial motivations for inflationary cosmology [51][52][53] (see [54,55] for some recent investigations). In general, inflationary models have a large number of e-folds, and hence our Universe should be very closed to spatially flat.…”

Section: Spatial Curvaturementioning

confidence: 99%

Implications for cosmology from ground-based Cosmic Microwave Background observations

Wang

Huang

2020

J. Cosmol. Astropart. Phys.

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Cosmic Microwave Background (CMB) anisotropy encodes a lot of information about our Universe. In this paper we take the ground-based CMB observations (GCMB), including the South Pole Telescope (SPT), SPTpol and the Atacama Cosmology Telescope Polarimeter (ACTPol), as a new probe to the CMB anisotropy independent of two satellite observations, i.e. Wilkinson Microwave Anisotropy Probe (WMAP) and Planck. The combination of current GCMB data is consistent with WMAP and Planck. In the spatially flat ΛCDM model, the Hubble constant is H0=69.72± 1.63 km/s/Mpc at 68% confidence level (CL). Combining with baryon acoustic oscillation (BAO) and the Pantheon sample of Type Ia supernovae (SN), we find that H0=68.40± 0.58 km/s/Mpc (68% CL) in the spatially flat ΛCDM cosmology which has a tension with local measurement given by Riess et al. in 2019 at 3.7σ level, and Ωk=−0.0013± 0.0039 and Neff=2.90± 0.41 (68% CL) in the extended cosmological models.

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Measuring the tilt of primordial gravitational-wave power spectrum from observations

Cited by 30 publications

References 39 publications

Probing the equation of state of the early Universe with pulsar timing arrays

Probing the equation of state of the early Universe with pulsar timing arrays

Log-dependent slope of scalar induced gravitational waves in the infrared regions

Implications for cosmology from ground-based Cosmic Microwave Background observations

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