研究者詳細 - 泉　圭介

その他リンク： http://arxiv.org/pdf/2108.02588v1

Asymptotic behavior of null geodesics near future null infinity: Significance of gravitational waves Open Access

Amo, M; Izumi, K; Tomikawa, Y; Yoshino, H; Shiromizu, T

PHYSICAL REVIEW D 104 巻 ( 6 ) 2021年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review D

We investigate the behavior of null geodesics near future null infinity in asymptotically flat spacetimes. In particular, we focus on the asymptotic behavior of null geodesics that correspond to worldlines of photons initially emitted in the directions tangential to the constant radial surfaces in the Bondi coordinates. The analysis is performed for general dimensions, and the difference between the four-dimensional cases and the higher-dimensional cases is stressed. In four dimensions, some assumptions are required to guarantee the null geodesics to reach future null infinity, in addition to the conditions of asymptotic flatness. Without these assumptions, gravitational waves may prevent photons from reaching null infinity. In higher dimensions, by contrast, such assumptions are not necessary, and gravitational waves do not affect the asymptotic behavior of null geodesics.

DOI： 10.1103/PhysRevD.104.064025

Holographic entanglement entropy of deSitter braneworld with Lovelock

その他リンク： http://arxiv.org/pdf/2106.03150v3

Divergence equations and uniqueness theorem of static spacetimes with conformal scalar hair Open Access

Shinohara, T; Tomikawa, Y; Izumi, K; Shiromizu, T

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS 2021 巻 ( 9 ) 2021年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Progress of Theoretical and Experimental Physics

We reexamine the Israel-type proof of the uniqueness theorem of the static spacetime outside the photon surface in the Einstein-conformal scalar system. We derive in a systematic fashion a new divergence identity which plays a key role in the proof. Our divergence identity includes three parameters, allowing us to give a new proof of the uniqueness.

DOI： 10.1093/ptep/ptab107

その他リンク： http://arxiv.org/pdf/2107.13133v1

Area bound for surfaces in generic gravitational field

Izumi Keisuke, Tomikawa Yoshimune, Shiromizu Tetsuya, Yoshino Hirotaka

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS 2021 巻 ( 8 ) 2021年8月

Perturbative S-matrix unitarity (S*S=1) in R-mu nu(2) gravity

Abe Yugo, Inami Takeo, Izumi Keisuke

MODERN PHYSICS LETTERS A 36 巻 ( 16 ) 2021年5月

Holographic entanglement entropy of a de Sitter braneworld with Lovelock terms

Kushihara Kouki, Izumi Keisuke, Shiromizu Tetsuya

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS 2021 巻 ( 4 ) 2021年4月

Kouki Kushihara, Keisuke Izumi, Tetsuya Shiromizu

2021年2月

Area bound for surfaces in generic gravitational field

Keisuke Izumi, Yoshimune Tomikawa, Tetsuya Shiromizu, Hirotaka Yoshino

2021年1月

We define an attractive gravity probe surface (AGPS) as a compact 2-surface
$S_\alpha$ with positive mean curvature $k$ satisfying $r^a D_a k / k^2 \ge
\alpha$ (for a constant $\alpha>-1/2$) in the local inverse mean curvature
flow, where $r^a D_a k$ is the derivative of $k$ in the outward unit normal
direction. For asymptotically flat spaces, any AGPS is proved to satisfy the
areal inequality $A_\alpha \le 4\pi [ ( 3+4\alpha)/(1+2\alpha) ]^2(Gm)^2$,
where $A_{\alpha}$ is the area of $S_\alpha$ and $m$ is Arnowitt-Deser-Misner
(ADM) mass. Equality is realized when the space is isometric to the
$t=$constant hypersurface of the Schwarzschild spacetime and $S_\alpha$ is an
$r=\mathrm{constant}$ surface with $r^a D_a k / k^2 = \alpha$. We adapt the two
methods, the inverse mean curvature flow and the conformal flow. Therefore, our
result is applicable to the case where $S_\alpha$ has multiple components. For
anti-de Sitter (AdS) spaces, the similar inequality is derived, but the proof
is performed only by using the inverse mean curvature flow. We also discuss the
cases with asymptotically locally AdS spaces.

その他リンク： http://arxiv.org/pdf/2101.03860v1

Invertible field transformations with derivatives: necessary and sufficient conditions 国際共著 Open Access

Babichev E., Izumi K., Tanahashi N., Yamaguchi M.

Advances in Theoretical and Mathematical Physics 25 巻 ( 2 ) 頁： 309 - 325 2021年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Advances in Theoretical and Mathematical Physics

We formulate explicitly the necessary and sufficient conditions for the local invertibility of a field transformation involving derivative terms. Our approach is to apply the method of characteristics of differential equations, by treating such a transformation as differential equations that give new variables in terms of original ones. The obtained results generalise the well-known and widely used inverse function theorem. Taking into account that field transformations are ubiquitous in modern physics and mathematics, our criteria for invertibility will find many useful applications.

DOI： 10.4310/ATMP.2021.v25.n2.a2

DOI： 10.4310/atmp.2021.v25.n2.a2

Invertible field transformations with derivatives: necessary and sufficient conditions

その他リンク： http://arxiv.org/pdf/1907.12333v1

Babichev, E; Izumi, K; Tanahashi, N; Yamaguchi, M

ADVANCES IN THEORETICAL AND MATHEMATICAL PHYSICS 25 巻 ( 2 ) 頁： 309 - 325 2021年

Perturbative $S$-matrix unitarity ($S^{\dagger}S=1$) in $R_{μν} ^2$ gravity

Yugo Abe, Takeo Inami, Keisuke Izumi

2020年12月

We show that in the quadratic curvature theory of gravity, or simply $R_{\mu
\nu} ^2$ gravity, the tree-level unitariy bound (tree unitarity) is violated in
the UV region but an analog for $S$-matrix unitarity ($SS^{\dagger} = 1$) is
satisfied. This theory is renormalizable, and hence the failure of tree
unitarity is a counter example of Llewellyn Smith's conjecture on the relation
between them. We have recently proposed a new conjecture that $S$-matrix
unitarity gives the same conditions as renormalizability. We verify that
$S$-matrix unitarity holds in the matter-graviton scattering at tree level in
the $R_{\mu \nu} ^2$ gravity, demonstrating our new conjecture.

その他リンク： http://arxiv.org/pdf/2012.01717v3

Loosely trapped surface and dynamically transversely trapping surface in Einstein-Maxwell systems 査読有り国際誌

Lee K., Shiromizu T., Yoshino H., Izumi K., Tomikawa Y.

Progress of Theoretical and Experimental Physics 2020 巻 ( 10 ) 2020年10月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Progress of Theoretical and Experimental Physics

We study the properties of the loosely trapped surface (LTS) and the dynamically transversely trapping surface (DTTS) in Einstein-Maxwell systems. These concepts of surfaces were proposed by four of the present authors in order to characterize strong gravity regions. We prove the Penrose-like inequalities for the area of LTSs/DTTSs. Interestingly, although the naively expected upper bound for the area is that of the photon sphere of a Reissner-Nordström black hole with the same mass and charge, the obtained inequalities include corrections represented by the energy density or pressure/tension of electromagnetic fields. Due to this correction, the Penrose-like inequality for the area of LTSs is tighter than the naively expected one. We also evaluate the correction term numerically in the Majumdar-Papapetrou two-black-hole spacetimes.

DOI： 10.1093/ptep/ptaa133

その他リンク： http://arxiv.org/pdf/2007.03139v1

Formation of dynamically transversely trapping surfaces and the stretched hoop conjecture 査読有り国際誌 Open Access

Yoshino, H; Izumi, K; Shiromizu, T; Tomikawa, Y

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS 2020 巻 ( 5 ) 2020年5月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Progress of Theoretical and Experimental Physics

A dynamically transversely trapping surface (DTTS) is a new concept for an extension of a photon sphere that appropriately represents a strong gravity region and has close analogy with a trapped surface. We study formation of a marginally DTTS in time-symmetric, conformally flat initial data with two black holes, with a spindle-shaped source, and with a ring-shaped source, and clarify that C ≲ 6π GM describes the condition for the DTTS formation well, where C is the circumference and M is the mass of the system. This indicates that an understanding analogous to the hoop conjecture for the horizon formation is possible. Exploring the ring system further, we find configurations where a marginally DTTS with the torus topology forms inside a marginally DTTS with the spherical topology, without being hidden by an apparent horizon. There also exist configurations where a marginally trapped surface with the torus topology forms inside a marginally trapped surface with the spherical topology, showing a further similarity between DTTSs and trapped surfaces.

DOI： 10.1093/ptep/ptaa050

その他リンク： http://arxiv.org/pdf/1911.09893v2

Transversely trapping surfaces: Dynamical version 査読有り国際誌 Open Access

Yoshino, H; Izumi, K; Shiromizu, T; Tomikawa, Y

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS 2020 巻 ( 2 ) 2020年2月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Progress of Theoretical and Experimental Physics

We propose new concepts, a dynamically transversely trapping surface (DTTS) and a marginally DTTS, as indicators for a strong gravity region. A DTTS is defined as a two-dimensional closed surface on a spacelike hypersurface such that photons emitted from arbitrary points on it in transverse directions are acceleratedly contracted in time, and a marginally DTTS is reduced to the photon sphere in spherically symmetric cases. (Marginally) DTTSs have a close analogy with (marginally) trapped surfaces in many aspects. After preparing the method of solving for a marginally DTTS in the time-symmetric initial data and the momentarily stationary axisymmetric initial data, some examples of marginally DTTSs are numerically constructed for systems of two black holes in the Brill-Lindquist initial data and in the Majumdar-Papapetrou spacetimes. Furthermore, the area of a DTTS is proved to satisfy the Penrose-like inequality A0 ≤ 4π (3GM)2, under some assumptions. Differences and connections between a DTTS and the other two concepts proposed by us previously, a loosely trapped surface [Prog. Theor. Exp. Phys. 2017, 033E01 (2017)] and a static/stationary transversely trapping surface [Prog. Theor. Exp. Phys. 2017, 063E01 (2017)], are also discussed. A (marginally) DTTS provides us with a theoretical tool to significantly advance our understanding of strong gravity fields. Also, since DTTSs are located outside the event horizon, they could possibly be related with future observations of strong gravity regions in dynamical evolutions.

DOI： 10.1093/ptep/ptz161

その他リンク： http://arxiv.org/pdf/1909.08420v2

S-matrix unitarity and renormalizability in higher-derivative theories 査読有り国際誌 Open Access

Abe, Y; Inami, T; Izumi, K; Kitamura, T; Noumi, T

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS 2019 巻 ( 8 ) 2019年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Progress of Theoretical and Experimental Physics

We investigate the relation between S-matrix unitarity (SS†=1) and renormalizability in theories with negative-norm states. The relation has been confirmed in many field theories, including gauge theories and Einstein gravity, by analyzing the unitarity bound, which follows from the S-matrix unitarity and the norm positivity. On the other hand, renormalizable theories with a higher-derivative kinetic term do not necessarily satisfy the unitarity bound because of the negative-norm states. In these theories it is not known whether the S-matrix unitarity provides a nontrivial constraint related to the renormalizability. In this paper, by relaxing the assumption of norm positivity we derive a bound on scattering amplitudes weaker than the unitarity bound, which may be used as a consistency requirement for S-matrix unitarity. We demonstrate in scalar field models with a higher-derivative kinetic term that the weaker bound and the renormalizability imply identical constraints.

DOI： 10.1093/ptep/ptz084

その他リンク： http://arxiv.org/pdf/1805.00262v1

Divergence equations and uniqueness theorem of static black holes 査読有り国際誌 Open Access

Nozawa, M; Shiromizu, T; Izumi, K; Yamada, S

CLASSICAL AND QUANTUM GRAVITY 35 巻 ( 17 ) 2018年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Classical and Quantum Gravity

Equations of divergence type in static spacetimes play a significant role in the proof of uniqueness theorems of black holes. We generalize the divergence equation originally discovered by Robinson in four dimensional vacuum spacetimes into several directions. We find that the deviation from spherical symmetry is encoded in a symmetric trace-free tensor H ij on a static timeslice. This tensor is the crux for the construction of the desired divergence equation, which allows us to conclude the uniqueness of the Schwarzschild black hole without using Smarr's integration mass formula. In Einstein-Maxwell(-dilaton) theory, we apply the maximal principle for a number of divergence equations to prove the uniqueness theorem of static black holes. In higher dimensional vacuum spacetimes, a central obstruction for applicability of the current proof is the integration of the -dimensional scalar curvature over the horizon cross-section, which has been evaluated to be a topological constant by the Gauss-Bonnet theorem for n = 4. Nevertheless, it turns out that the -dimensional symmetric and traceless tensor H ij is still instrumental for the modification of the uniqueness proof based upon the positive mass theorem, as well as for the derivation of the Penrose-type inequality.

DOI： 10.1088/1361-6382/aad206

Matter scattering and unitarity in Horava-Lifshitz gravity

その他リンク： http://arxiv.org/pdf/1805.11385v2

Matter scattering in quadratic gravity and unitarity 査読有り国際誌 Open Access

Abe, Y; Inami, T; Izumi, K; Kitamura, T

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS 2018 巻 ( 3 ) 2018年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Progress of Theoretical and Experimental Physics

We investigate the ultraviolet (UV) behavior of two-scalar elastic scattering 
with graviton exchanges in higher curvature gravity theory. In the Einstein 
gravity, matter scattering is shown not to satisfy tree unitarity at high 
energy. Among a few possible directions to cure unitarity (i.e. UV completion 
of Einstein gravity), string theory, modified gravity, inclusion of 
high-mass/high-spin states, we take $R_{\mu\nu}^2$ gravity coupled to matter. 
We show that the matter scattering with graviton interactions satisfies the 
unitarity bound at high energy, in contrast with the Einstein gravity. The 
difference in unitarity property of the two gravity theories is due to that in 
the UV behavior of the propagator and is probably connected to that in another 
UV property, namely renormalizability property of the two.

DOI： 10.1093/ptep/pty010

その他リンク： http://arxiv.org/pdf/1712.06305v2

Kitamura T., Inami T., Izumi K.

Proceedings of the 28th Workshop on General Relativity and Gravitation in Japan, JGRG 2018 2 巻頁： 105 - 116 2018年

On uniqueness of static spacetimes with non-trivial conformal scalar field 査読有り国際誌

Tomikawa, Y; Shiromizu, T; Izumi, K

CLASSICAL AND QUANTUM GRAVITY 34 巻 ( 15 ) 2017年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Classical and Quantum Gravity

We discuss the uniqueness of static spacetimes with non-trivial conformal scalar field. We can show that the spacetime is unique to be the Bocharova-Bronnikov-Melnikov-Bekenstein solution outside the surface composed of the unstable circular orbit of a photon (photon surface). In addition, we see that multiple disconnected photon surfaces having the same values of the scalar field do not exist.

DOI： 10.1088/1361-6382/aa7906