155 citations · 1.2k across the 32 of their papers we have counts for
32 papers
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…
Supermassive primordial black holes in multiverse: for nano-Hertz gravitational wave and high-redshift JWST galaxies
Hai-Long Huang, Yong Cai, Jun-Qian Jiang +2
Recently, observational hints for supermassive black holes have been accumulating, which has inspired ones to wonder: Can primordial black holes (PBHs) be supermassive, in particul…
Primordial black holes from null energy condition violation during inflation
Yong Cai, Mian Zhu, Yun-Song Piao
Primordial black holes (PBHs) and the violation of the null energy condition (NEC) have significant implications for our understanding of the very early universe. We present a nove…
Parity-violation in bouncing cosmology
Mian Zhu, Yong Cai
We investigate the possibility of the enhancement of parity-violation signal in bouncing cosmology. Specifically, we are interested in deciding which phase should generate the most…
Generating enhanced parity-violating gravitational waves during inflation with violation of the null energy condition
Yong Cai
A violation of the null energy condition (NEC) during inflation in a single-field inflation model will naturally enhance the amplitude of the parity violation effect (defined by $Δ…
Perturbative unitarity and NEC violation in genesis cosmology
Yong Cai, Ji Xu, Shuai Zhao +1
Explorations of the violation of null energy condition (NEC) in cosmology could enrich our understanding of the very early universe and the related gravity theories. Although a ful…
Generating enhanced primordial GWs during inflation with intermittent violation of NEC and diminishment of GW propagating speed
Yong Cai, Yun-Song Piao
We investigate both the null energy condition (NEC) violating scenario and the -diminishing scenario for generating enhanced power spectrum of primordial gravitational waves (…
SN 2015bf: a fast declining type II supernova with flash-ionised signatures
Han Lin, Xiaofeng Wang, Jujia Zhang +19
We present optical and ultraviolet photometry, as well as optical spectra, for the type II supernova (SN) 2015bf. Our observations cover the phases from to d af…
Intermittent null energy condition violations during inflation and primordial gravitational waves
Yong Cai, Yun-Song Piao
Primordial null energy condition (NEC) violation would imprint a blue-tilted spectrum on gravitational wave background (GWB). However, its implications on the GWB might be far rich…
Trans-Planckian censorship of multistage inflation and dark energy
Hao-Hao Li, Gen Ye, Yong Cai +1
We explore the bound of the trans-Planckian censorship conjecture on an inflation model with multiple stages. We show that if the first inflationary stage is responsible for the pr…
Pre-inflation and Trans-Planckian Censorship
Yong Cai, Yun-Song Piao
We investigate the implication of Trans-Planckian Censorship Conjecture (TCC) for the initial state of primordial perturbations. It is possible to set the state of perturbation mod…
Perturbative Reheating in Sneutrino-Higgs Cosmology
Yong Cai, Rehan Deen, Burt A. Ovrut +1
The theory of perturbative reheating in the Sneutrino-Higgs cosmology of the MSSM is presented. It is shown that following an epoch of inflation consistent with all Planck201…
The effective field theory approach of teleparallel gravity, gravity and beyond
Chunlong Li, Yong Cai, Yi-Fu Cai +1
We develop the effective field theory approach to torsional modified gravities, a formalism that allows for the systematic investigation of the background and perturbation levels s…
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…
Higher order derivative coupling to gravity and its cosmological implications
Yong Cai, Yun-Song Piao
We show that the operator in effective field theory is significant for avoiding the instability of nonsingular bounce, where and are the three-dimens…
A covariant Lagrangian for stable nonsingular bounce
Yong Cai, Yun-Song Piao
The nonsingular bounce models usually suffer from the ghost or gradient instabilities, as has been proved recently. In this paper, we propose a covariant effective theory for stabl…
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…
The Effective Field Theory of nonsingular cosmology: II
Yong Cai, Hai-Guang Li, Taotao Qiu +1
Based on the Effective Field Theory (EFT) of cosmological perturbations, we explicitly clarify the pathology in nonsingular cubic Galileon models and show how to cure it in EFT wit…
The Effective Field Theory of nonsingular cosmology
Yong Cai, Youping Wan, Hai-Guang Li +2
In this paper, we explore the nonsingular cosmology within the framework of the Effective Field Theory(EFT) of cosmological perturbations. Due to the recently proved no-go theorem,…