arXiv subjects

Guang-Hai Guo

Publications and source records attributed to Guang-Hai Guo.

4 recordsLinked to original sources

arXiv2023

Measuring the speed of scalar induced gravitational waves from observations

We investigate the scalar induced gravitational waves which propagate with a speed different from the speed of light. First, we analytically calculate the expression of the power spectrum of the scalar induced gravitational waves which is based on the speed and the spectrum of the primordial curvature perturbations. Then, we discuss several scalar power spectra and obtain corresponding fractional energy density, such as the monochromatic power spectrum, the scale invariant power spectrum and the power-law power spectrum. Finally, we constrain the scalar induced gravitational waves and evaluate the signatures of the speed from the combination of CMB+BAO and gravitational waves observations. The numerical results are obvious to reveal the influence of speed of scalar induced gravitational waves.

gr-qc↗

arXiv2023

Measuring the primordial curvature perturbations from the scalar induced gravitational waves

The scalar induced gravitational waves are produced from primordial curvature perturbations in the second order of perturbations. We constrain the fractional energy density of scalar induced gravitational waves from gravitational waves observations. If there is no detection of the scalar induced gravitational waves, the fractional energy density of scalar induced gravitational waves is constrained by some upper limits. Depends on these upper limits, we can obtain the constraints on the power spectrum of the primordial curvature perturbations. For a power-law scalar power spectrum, the constraints on the power spectrum are affected by adding the upper limit of scalar induced gravitational waves from Square Kilometer Array (SKA). In the standard model, the mean values of the scalar amplitude and the spectral index shift to lower values when SKA is added to the combination of Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillation (BAO) datasets, namely $\ln(10^{10}A_s)=3.038\pm0.013$ and $n_s=0.9589^{+0.0021}_{-0.0011}$ at $68\%$ confidence level. We also consider the effects of the existing ground-based gravitational-wave detectors, the existing Pulsar Timing Arrays (PTAs) and Five-hundred-meter Aperture Spherical radio Telescope (FAST), while the constraints from CMB+BAO datasets are totally within their upper limits of scalar induced gravitational waves. Furthermore, we characterize the scalar fluctuation spectrum in terms of the spectral index $n_s$ and its first two derivatives. We calculate corresponding power spectrum of scalar induced gravitational waves theoretically and give the constraints on the running of the spectral index and the running of the running of the spectral index.

astro-ph.CO↗

arXiv2022

Measuring the primordial gravitational waves from cosmic microwave background and stochastic gravitational wave background observations

We constrain the primordial gravitational waves from cosmic microwave background (CMB) and stochastic gravitational wave background (SGWB) observations. SGWB provides the latest way to explore the early universe and the cosmological evolution which can be reflected by primordial gravitational waves. We not only combine LIGO observations with CMB to measure primordial gravitational waves, but also forecast the potential abilities of the LISA detector and PTA projects. In the $Λ$CDM+$r$+$n_t$ model, the standard six parameters change slightly from SGWB observations. While the constraints on tensor-to-scalar ratio and tensor spectral index are improved obviously from SGWB observations. FAST projects have a significant impact on tensor-to-scalar ratio and tensor spectral index, namely $r<0.028$ and $n_t=-0.41^{+0.64}_{-0.96}$ at $95\%$ confidence level.

astro-ph.CO↗

arXiv2021

Measuring the scalar induced gravitational waves from observations

We measure the scalar induced gravitational waves from the cosmic microwave background (CMB) observations and the gravitational wave observations. In the $Λ$CDM+$r$ model, we constrain the cosmological parameters within the evolution of the scalar induced gravitational waves by the additional scalar power spectrum. The two special cases called narrow power spectrum and wide power spectrum have influence on the cosmological parameters, especially the combinations of Planck18+BAO+BK15+LISA. We also compare these numerical results from four datasets within LIGO, LISA, IPTA and FAST projects, respectively. The constraints from FAST have a significant impact on tensor-to-scalar ratio.

astro-ph.CO↗