arXiv subjects

Rong-gen Cai

Publications and source records attributed to Rong-gen Cai.

3 recordsLinked to original sources

arXiv2025

Generic effective sources for first-order in mass-ratio gravitational self-force calculations in Schwarzschild spacetime

The numerical calculation of gravitational self-force in extreme mass ratio inspiral systems is fundamentally challenging due to the singular nature of point-particle sources. To overcome these difficulties, the effective source method offers an innovative alternative by replacing traditional regularization techniques with a reformulation of the problem. In this paper, we present the first fully analytic framework for constructing effective sources to compute the gravitational self-force for generic orbits in Schwarzschild spacetime. By reformulating the singular field through angular modulation in terms of a tetrad decomposition, the effective source can be constructed with the linear combination of scalar modes. The derived effective source is continuous across the particle's worldline, enabling efficient numerical implementation in $1+1$ dimensions.

gr-qc↗

arXiv2019

Gravitational Waves Induced by non-Gaussian Scalar Perturbations

We study gravitational waves (GWs) induced by non-Gaussian curvature perturbations. We calculate the density parameter per logarithmic frequency interval, $Ω_\text{GW}(k)$, given that the power spectrum of the curvature perturbation $\mathcal{P}_\mathcal{R}(k)$ has a narrow peak at some small scale $k_*$, with a local-type non-Gaussianity, and constrain the nonlinear parameter $f_\text{NL}$ with the future LISA sensitivity curve as well as with constraints from the abundance of the primordial black holes (PBHs). We find that the non-Gaussian contribution to $Ω_\text{GW}$ increases as $k^3$, peaks at $k/k_*=4/\sqrt{3}$, and has a sharp cutoff at $k=4k_*$. The non-Gaussian part can exceed the Gaussian part if $\mathcal{P}_\mathcal{R}(k)f_\text{NL}^2\gtrsim1$. If both a slope $Ω_\text{GW}(k)\propto k^β$ with $β\sim3$ and the multiple-peak structure around a cutoff are observed, it can be recognized as a smoking gun of the primordial non-Gaussianity. We also find that if PBHs with masses of $10^{20}\text{g}$ to $10^{22}\text{g}$ are identified as cold dark matter of the Universe, the corresponding GWs must be detectable by LISA-like detectors, irrespective of the value of $\mathcal{P}_\mathcal{R}$ or $f_\text{NL}$.

astro-ph.CO↗

arXiv2010

Probing the cosmic acceleration from combinations of different data sets

We examine in some detail the influence of the systematics in different data sets including type Ia supernova sample, baryon acoustic oscillation data and the cosmic microwave background information on the fitting results of the Chevallier-Polarski-Linder parametrization. We find that the systematics in the data sets does influence the fitting results and leads to different evolutional behavior of dark energy. To check the versatility of Chevallier-Polarski-Linder parametrization, we also perform the analysis on the Wetterich parametrization of dark energy. The results show that both the parametrization of dark energy and the systematics in data sets influence the evolutional behavior of dark energy.

astro-ph.CO↗