109 citations · 613 across the 27 of their papers we have counts for
27 papers
Charged multi-sheet wormhole solutions
Yusuke Makita, Keisuke Izumi, Daisuke Yoshida
We construct charged wormhole solutions with an even number of asymptotically flat regions in the four-dimensional Einstein-Maxwell-massless phantom scalar system via the Harrison…
Entropy Bound and a Geometrically Nonsingular Universe
Takamasa Kanai, Kimihiro Nomura, Daisuke Yoshida
Bousso's entropy bound is a conjecture that the entropy through a null hypersurface emanating from a two-dimensional surface with a nonpositive expansion is bounded by the area of…
Implications of the singularity theorem for the size of a nonsingular universe
Kimihiro Nomura, Daisuke Yoshida
A general property of universes without initial singularity is investigated based on the singularity theorem, assuming the null convergence condition and the global hyperbolicity.…
Quasinormal modes of charged black holes with corrections from nonlinear electrodynamics
Kimihiro Nomura, Daisuke Yoshida
We study quasinormal modes related to gravitational and electromagnetic perturbations of spherically symmetric charged black holes in nonlinear electrodynamics. Beyond the linear M…
String Excitation by Initial Singularity of Inflation
Kanji Nishii, Daisuke Yoshida
We discuss excitation of string oscillation modes by an initial singularity of inflation. The initial singularity of inflation is known to occur with a finite Hubble parameter, whi…
Past extendibility and initial singularity in Friedmann-Lemaître-Robertson-Walker and Bianchi I spacetimes
Kimihiro Nomura, Daisuke Yoshida
We study past-directed extendibility of Friedmann-Lemaître-Robertson-Walker (FLRW) and Bianchi type I spacetimes with a scale factor vanishing in the past. We give criteria for det…