23 citations · 30 across the 14 of their papers we have counts for
14 papers
Anisotropic separate universe : Long-wavelength perturbations and conserved quantities
Daiki Saito, Atsushi Naruko
We investigate the long-wavelength evolution of linear perturbations in a homogeneous and anisotropic background with a scalar field coupled to a vector field. Using the spatial gr…
Refocusing of Wheeler--DeWitt wave functions at inner horizons
Takeshi Chiba, Keiju Murata, Daiki Saito
We study quantum gravitational effects inside hyperbolic black holes with both outer and inner horizons by solving the Wheeler--DeWitt (WDW) equation in the minisuperspace approxim…
COSMOS: A numerical relativity code specialized for PBH formation
Chul-Moon Yoo, Hirotada Okawa, Albert Escrivà +7
Primordial black holes (PBHs) are black holes generated in the early universe without having gone through stellar evolution. In the standard formation process, PBHs are formed from…
Primordial black holes in excursion set theory: Formation probabilities, mass functions, and window functions
Hayami Iizuka, Daiki Saito, Koki Tokeshi
We study the mass function of primordial black holes (PBHs) within the excursion-set theory, in which the response of the stochastic density contrast to the variation of the coarse…
Rotating wormholes in five dimensions with equal angular momenta: large asymmetry regime
Keiya Uemichi, Yasutaka Koga, Daiki Saito +2
We clarify the relationship between rotation and the energy condition for stationary rotating wormhole solutions of the Einstein equations coupled to a phantom field in five-dimens…
Dynamical Formation of Self-Similar Wormholes
Yasutaka Koga, Ryota Maeda, Daiki Saito +1
We study spherically symmetric, self-similar wormhole solutions supported by colliding streams of negative-energy null dust, and their dynamical formation. Under the assumption of…
Primordial Black Hole Formation and Spin in Matter Domination Revisited
Weitao Ye, Yungui Gong, Tomohiro Harada +4
In this article, we calculate the mass distribution of primordial black holes (PBHs) formed in the matter-dominated (MD) era by the peak theory. We apply the Zel'dovich approximati…
Dynamical Formation of Charged Wormholes
Yasutaka Koga, Ryota Maeda, Daiki Saito +2
We construct static, spherically symmetric, charged traversable wormhole solutions to the Einstein--Maxwell equations, supported by bidirectional (ingoing and outgoing) null dust w…
Primordial black hole formation from a type II perturbation in the absence and presence of pressure
Koichiro Uehara, Albert Escrivà, Tomohiro Harada +2
We investigate primordial black holes (PBHs) formed from extremely large amplitudes of primordial curvature fluctuations, classified as type II. Type II fluctuations differ from ty…
Primordial Black Hole Formation from Type II Fluctuations with Primordial Non-Gaussianity
Masaaki Shimada, Albert Escrivá, Daiki Saito +2
This study investigates the formation of primordial black holes (PBHs) resulting from the collapse of adiabatic fluctuations with large amplitudes and non-Gaussianity. Ref. \cite{U…
Removing naked singularities in static axially symmetric spacetimes by patching with the flat spacetimes
Daiki Saito, Daisuke Yoshida
We investigate static, axially symmetric spacetimes without naked singularities that are constructed by patching Weyl class spacetimes with the flat spacetimes. Once the exterior g…
Remote Hawking-Moss instanton and the Lorentzian path integral
Daiki Saito, Naritaka Oshita
The Hawking-Moss (HM) bounce solution implies that the tunneling amplitude between vacua is uniquely determined by the vacuum energy at the initial vacuum and the top of a potentia…
Revisiting spins of primordial black holes in a matter-dominated era based on peak theory
Daiki Saito, Tomohiro Harada, Yasutaka Koga +1
We estimate the probability distribution for the spins of the primordial black holes (PBHs) that formed during an early matter-dominated era in the Universe. We employ the Zel'dovi…
Numerical simulation of type II primordial black hole formation
Koichiro Uehara, Albert Escrivà, Tomohiro Harada +2
This study investigates the formation of type II primordial black holes (PBHs) resulting from extremely large amplitudes of initial fluctuations in a radiation-dominated universe.…