155 citations · 1.2k across the 32 of their papers we have counts for
13 papers · 1 filter
Parity-violating primordial gravitational waves from null energy condition violation
Zi-Wei Jiang, Yong Cai, Fei Wang +1
We investigate the parity-violating effects in primordial gravitational waves (GWs) due to null energy condition (NEC) violation in two very early universe scenarios: bounce-inflat…
Climbing over the potential barrier during inflation via null energy condition violation
Shi Pan, Yong Cai, Yun-Song Piao
The violation of the null energy condition (NEC) may play a crucial role in enabling a scalar field to climb over high potential barriers, potentially significant in the very early…
Pulsar timing array observations as possible hints for nonsingular cosmology
Mian Zhu, Gen Ye, Yong Cai
Recent pulsar timing array (PTA) experiments have reported strong evidence of the stochastic gravitational wave background (SGWB). If interpreted as primordial gravitational waves…
Broken blue-tilted inflationary gravitational waves: a joint analysis of NANOGrav 15-year and BICEP/Keck 2018 data
Jun-Qian Jiang, Yong Cai, Gen Ye +1
Recently, the pulsar timing array (PTA) collaborations have reported the evidence for a stochastic gravitational wave background (SGWB) at nano-Hertz band. The spectrum of inflatio…
Phase-transition sound of inflation at gravitational waves detectors
Yu-Tong Wang, Yong Cai, Yun-Song Piao
It is well-known that the first-order phase transition (PT) will yield a stochastic gravitational waves (GWs) background with a logo-like spectrum. However, we show that when such…
Primordial perturbations with pre-inflationary bounce
Yong Cai, Yu-Tong Wang, Jin-Yun Zhao +1
Based on the effective field theory (EFT) of nonsingular cosmologies, we build a stable model, without the ghost and gradient instabilities, of bounce inflation (inflation is prece…
Probing the primordial universe with gravitational waves detectors
Yu-Tong Wang, Yong Cai, Zhi-Guo Liu +1
The spectrum of primordial gravitational waves (GWs), especially its tilt , carries significant information about the primordial universe. Combining recent aLIGO and Planck201…
Test of parametrized post-Newtonian gravity with galaxy-scale strong lensing systems
Shuo Cao, Xiaolei Li, Marek Biesiada +3
Based on a mass-selected sample of galaxy-scale strong gravitational lenses from the SLACS, BELLS, LSD and SL2S surveys and using a well-motivated fiducial set of lens-galaxy param…
Chirality oscillation of primordial gravitational waves during inflation
Yong Cai, Yu-Tong Wang, Yun-Song Piao
We show that if the gravitational Chern-Simons term couples to a massive scalar field (), the primordial gravitational waves (GWs) will show itself the chirality oscillation,…
Propagating speed of primordial gravitational waves and inflation
Yong Cai, Yu-Tong Wang, Yun-Song Piao
We show that if the propagating speed of gravitational waves (GWs) gradually diminishes during inflation, the power spectrum of primordial GWs will be strongly blue, while that of…
Is there an effect of a nontrivial during inflation?
Yong Cai, Yu-Tong Wang, Yun-Song Piao
Recently, we have shown that the propagation speed of the primordial gravitational waves (GWs) might be nontrivially varying during inflation, which could induce local oscill…
Oscillating modulation to B-mode polarization from varying propagating speed of primordial gravitational waves
Yong Cai, Yu-Tong Wang, Yun-Song Piao
In low-energy effective string theory and modified gravity theories, the propagating speed of primordial gravitational waves may deviate from unity. We find that the step-lik…
Pre-inflationary primordial perturbations
Yong Cai, Yu-Tong Wang, Yun-Song Piao
The large-scale power deficit in the cosmic microwave background fluctuations might be relevant with the physics of pre-inflation, a bounce, or a superinflationary phase preceding…