109 citations · 613 across the 27 of their papers we have counts for
17 papers · 1 filter
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…
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…
Theories with limited extrinsic curvature and a nonsingular anisotropic universe
Yuki Sakakihara, Daisuke Yoshida, Kazufumi Takahashi +1
We propose a class of theories that can limit scalars constructed from the extrinsic curvature. Applied to cosmology, this framework allows us to control not only the Hubble parame…
Stability of magnetic black holes in general nonlinear electrodynamics
Kimihiro Nomura, Daisuke Yoshida, Jiro Soda
We study the perturbative stability of magnetic black holes in a general class of nonlinear electrodynamics, where the Lagrangian is given by a general function of the field streng…
Cuscuton gravity as a classically stable limiting curvature theory
Jerome Quintin, Daisuke Yoshida
Finding effective theories of modified gravity that can resolve cosmological singularities and avoid other physical pathologies such as ghost and gradient instabilities has turned…
Ghost-free resummation of gravitational interactions of a 2-form gauge field
Kazufumi Takahashi, Daisuke Yoshida
We find that the recently-proposed ghost-free interaction of a 2-form gauge field in four dimensions, which contains derivative couplings in a nonperturbative manner, can be regard…
Stable cosmological solutions in degenerate theory of gravity
Ryotaro Kase, Rampei Kimura, Atsushi Naruko +1
We study cosmological applications of extended vector-tensor theories, whose Lagrangians contain up to two derivatives with respect to metric and vector field. We derive background…
Maximal extensions and singularities in inflationary spacetimes
Daisuke Yoshida, Jerome Quintin
Extendibility of inflationary spacetimes with flat spatial geometry is investigated. We find that the past boundary of an inflationary spacetime becomes a so-called parallely propa…
Singularities in Spherically Symmetric Solutions with Limited Curvature Invariants
Daisuke Yoshida, Robert H. Brandenberger
We investigate static, spherically symmetric solutions in gravitational theories which have limited curvature invariants, aiming to remove the singularity in the Schwarzschild spac…
Extended vector-tensor theories
Rampei Kimura, Atsushi Naruko, Daisuke Yoshida
Recently, several extensions of massive vector theory in curved space-time have been proposed in many literatures. In this paper, we consider the most general vector-tensor theorie…
Note on Covariant Stückelberg Formalism and Absence of Boulware-Deser Ghost in Bi-gravity
Toshifumi Noumi, Masahide Yamaguchi, Daisuke Yoshida
The covariant Stückelberg formalism is applied to bi-gravity in order to revisit the issue of absence of the Boulware-Deser (BD) ghost. We first confirm that the leading order acti…
Gravitational scalar-tensor theory
Atsushi Naruko, Daisuke Yoshida, Shinji Mukohyama
We consider a new form of theories of gravity in which the action is written in terms of the Ricci scalar and its first and second derivatives. Despite the higher derivative nature…
Perturbations of Cosmological and Black Hole Solutions in Massive gravity and Bi-gravity
Tsutomu Kobayashi, Masaru Siino, Masahide Yamaguchi +1
We investigate perturbations of a class of spherically symmetric solutions in massive gravity and bi-gravity. The background equations of motion for the particular class of solutio…
Covariant Stückelberg analysis of de Rham-Gabadadze-Tolley massive gravity with a general fiducial metric
Xian Gao, Tsutomu Kobayashi, Masahide Yamaguchi +1
The Stückelberg analysis of nonlinear massive gravity in the presence of a general fiducial metric is investigated. We develop a "covariant" formalism for the Stückelberg expansion…