277 citations · 1k across the 23 of their papers we have counts for
23 papers
Primordial Black Hole Abundances and Scalar Induced Gravitational Waves from Finite-Width Power Spectra in a Stiff Thermal History
Abolhassan Mohammadi, Yogesh, Cristian Joana +2
We study the formation of primordial black holes (PBHs) from large primordial perturbations that re-enter the horizon during an epoch with equation of state . We co…
Reconstruction of Primordial Power Spectrum from Gravitational Waves of High-Redshift Black Hole Binaries
Qianhang Ding, Xinpeng Wang, Masahide Yamaguchi +1
High-redshift binary black hole (BBH) events are promising candidates for primordial black holes (PBHs) detectable by next-generation gravitational wave (GW) detectors. A redshifte…
Gauge-independent approach to inflation in quadratic gravity
Adrian Palomares, Ying-li Zhang, Jinsu Kim
We investigate the scalar sector of linear cosmological perturbations in quadratic gravity. Working in the Einstein frame, we derive the equations of motion in a gauge-independent…
The Dual Primordial Black Hole Formation Scenario
Xinpeng Wang, Misao Sasaki, Ying-li Zhang
We report a novel mechanism where two families of primordial black holes (PBHs) may form at nearly the same comoving scales but at two different epochs. It is realized in two-stage…
Singular instantons with finite action
Misao Sasaki, Vicharit Yingcharoenrat, Ying-li Zhang
Recently, it was shown that in the absence of gravity there exist non--symmetric instanton solutions with finite action beyond Coleman's instantons. In this paper, focusing o…
Beyond Coleman's Instantons
Misao Sasaki, Vicharit Yingcharoenrat, Ying-li Zhang
In the absence of gravity, Coleman's theorem states that the -symmetric instanton solution, which is regular at the origin and exponentially decays at infinity, gives the low…
Enhanced Curvature Perturbation and Primordial Black Hole Formation in Two-stage Inflation with a break
Xinpeng Wang, Ying-li Zhang, Misao Sasaki
We investigate a model of -gravity with a non-minimally coupled scalar field that gives rise to two-stage inflation with a break, that is, with an intermediate stage where inf…
Reconstruction of Power Spectrum of Primordial Curvature Perturbations on small scales from Primordial Black Hole Binaries scenario of LIGO/VIRGO detection
Xinpeng Wang, Ying-li Zhang, Rampei Kimura +1
As a candidate bound for the Binary Black Hole (BBH) merger events detected by LIGO/Virgo, Primordial Black Holes (PBHs) provide a useful tool to investigate the primordial curvatu…
Establishing the Non-Primordial Origin of Black Hole-Neutron Star Mergers
Misao Sasaki, Volodymyr Takhistov, Valeri Vardanyan +1
Primordial black holes (PBHs) from the early Universe constitute an attractive dark matter candidate. First detections of black hole-neutron star (BH-NS) candidate gravitational wa…
Primordial Tensor Perturbation in Double Inflationary Scenario with a Break
Shi Pi, Misao Sasaki, Ying-li Zhang
We study the primordial tensor perturbation produced from the double inflationary scenario with an intermediate break stage. Because of the transitions, the power spectrum deviates…
Scalaron from -gravity as a Heavy Field
Shi Pi, Ying-li Zhang, Qing-Guo Huang +1
We study a model of inflation in which a scalar field is non-minimally coupled to Starobinsky's gravity. After transforming it to the Einstein frame, a new scalar field,…
Stable solutions of inflation driven by vector fields
Razieh Emami, Shinji Mukohyama, Ryo Namba +1
Many models of inflation driven by vector fields alone have been known to be plagued by pathological behaviors, namely ghost and/or gradient instabilities. In this work, we seek a…
Effective gravitational couplings for cosmological perturbations in generalized Proca theories
Antonio De Felice, Lavinia Heisenberg, Ryotaro Kase +3
We consider the finite interactions of the generalized Proca theory including the sixth-order Lagrangian and derive the full linear perturbation equations of motion on the flat Fri…
Screening fifth forces in generalized Proca theories
Antonio De Felice, Lavinia Heisenberg, Ryotaro Kase +3
For a massive vector field with derivative self-interactions, the breaking of the gauge invariance allows the propagation of a longitudinal mode in addition to the two transverse m…
Acausality in Nonlocal Gravity Theory
Ying-li Zhang, Kazuya Koyama, Misao Sasaki +1
We investigate the nonlocal gravity theory by deriving nonlocal equations of motion using the traditional variation principle in a homogeneous background. We focus on a class of mo…
Homogeneous Instantons in Bigravity
Ying-li Zhang, Misao Sasaki, Dong-han Yeom
We study homogeneous gravitational instantons, conventionally called the Hawking-Moss (HM) instantons, in bigravity theory. The HM instantons describe the amplitude of quantum tunn…
Scalar suppression on large scales in open inflation
Jonathan White, Ying-li Zhang, Misao Sasaki
We consider two toy models of open inflation and investigate their ability to give a suppression of scalar power on large scales whilst also satisfying observational constraints on…
Coleman-de Luccia instanton in dRGT massive gravity
Ying-li Zhang, Ryo Saito, Dong-han Yeom +1
We study the Coleman-de Luccia (CDL) instanton characterizing the tunneling from a false vacuum to the true vacuum in a semi-classical way in dRGT (deRham-Gabadadze-Tolley) massive…
Hartle-Hawking no-boundary proposal in dRGT massive gravity: Making inflation exponentially more probable
Misao Sasaki, Dong-han Yeom, Ying-li Zhang
It is known that the no-boundary proposal in the traditional Einstein gravity does not prefer inflation, that is, the probability of realizing a large number of e-folds is exponent…
Cosmological Solutions of a Nonlocal Model with a Perfect Fluid
Emilio Elizalde, Ekaterina O. Pozdeeva, Sergey Yu. Vernov +1
A nonlocal gravity model which does not assume the existence of a new dimensional parameter in the action and includes a function , with the d'Alembertian op…
Hawking-Moss instanton in nonlinear massive gravity
Ying-li Zhang, Ryo Saito, Misao Sasaki
As a first step toward understanding a lanscape of vacua in a theory of non-linear massive gravity, we consider a landscape of a single scalar field and study tunneling between a p…
Screening of cosmological constant in non-local cosmology
Ying-li Zhang, Misao Sasaki
We consider a model of non-local gravity with a large bare cosmological constant, , and study its cosmological solutions. The model is characterized by a function $f(ψ)=f_0 e^{α…
Screening of cosmological constant in non-local gravity
Shin'ichi Nojiri, Sergei D. Odintsov, Misao Sasaki +1
We discuss a possible mechanism to screen a cosmological constant in non-local gravity. We find that in a simple model of of non-local gravity with the Lagrangian of the form, $R+f…