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On the constant-roll inflation
Zhu Yi, Yungui Gong
The primordial power spectra of scalar and tensor perturbations during slow-roll inflation are usually calculated with the method of Bessel function approximation. For constant-rol…
Constraints on Horndeski Theory Using the Observations of Nordtvedt Effect, Shapiro Time Delay and Binary Pulsars
Shaoqi Hou, Yungui Gong
Alternative theories of gravity not only modify the polarization contents of the gravitational wave, but also affect the motions of the stars and the energy radiated away via the g…
Extended source effect on microlensing light curves by an Ellis wormhole
Naoki Tsukamoto, Yungui Gong
We can survey an Ellis wormhole which is the simplest Morris-Thorne wormhole in our galaxy with microlensing. The light curve of a point source microlensed by the Ellis wormhole sh…
Constraints on scalar-tensor theory of gravity by the recent observational results on gravitational waves
Yungui Gong, Eleftherios Papantonopoulos, Zhu Yi
The speed of gravitational waves provides us a new tool to test alternative theories of gravity. The constraint on the speed of gravitational waves from GW170817 and GRB170817A is…
Gravitational Wave Polarizations in Gravity and Scalar-Tensor Theory
Yungui Gong, Shaoqi Hou
The detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory opens a new era to use gravitational waves to test alternative theories of gravity.…
Inflationary attractors from nonminimal coupling
Zhu Yi, Yungui Gong
We show explicitly how the E model attractor is obtained from the general scalar-tensor theory of gravity with arbitrary conformal factors in the strong coupling limit. By using co…
Primordial black holes and second order gravitational waves from ultra-slow-roll inflation
Haoran Di, Yungui Gong
The next generation of space-borne gravitational wave detectors may detect gravitational waves from extreme mass-ratio inspirals with primordial black holes. To produce primordial…
Particle collision with an arbitrarily high center-of-mass energy near a Bañados-Teitelboim-Zanelli black hole
Naoki Tsukamoto, Kota Ogasawara, Yungui Gong
We consider a particle collision with a high center-of-mass energy near a Bañados-Teitelboim-Zanelli (BTZ) black hole. We obtain the center-of-mass energy of two general colliding…
The reconstruction of tachyon inflationary potentials
Qin Fei, Yungui Gong, Jiong Lin +1
We derive a lower bound on the field excursion for the tachyon inflation, which is determined by the amplitude of the scalar perturbation and the number of -folds before the end…
Polarizations of Gravitational Waves in Horndeski Theory
Shaoqi Hou, Yungui Gong, Yunqi Liu
We analyze the polarization content of gravitational waves in Horndeski theory. Besides the familiar plus and cross polarizations in Einstein's General Relativity, there is one mor…
Reconstruction of extended inflationary potentials for attractors
Qing Gao, Yungui Gong
We give the procedure to reconstruct the extended inflationary potentials for attractors and use the attractor and the constant-roll model as examples to show how to reconstruc…
de Sitter spacetime with a Becchi-Rouet-Stora quartet
Rio Saitou, Yungui Gong
We generalize the topological model recently proposed and investigate the cosmological perturbations of the model. The model has an exact de Sitter background solution associated w…
Polarizations of gravitational waves in gravity
Dicong Liang, Yungui Gong, Shaoqi Hou +1
We point out that there are only three polarizations for gravitational waves in gravity, and the polarization due to the massive scalar mode is a mix of the pure longitudina…