研究者詳細 - 泉　圭介

論文 - 泉　圭介

分割表示 89 件中 1 - 20 件目／全件表示 >>

Attractive gravity probe surface in the Einstein-Maxwell system Open Access

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

Physical Review D 110 巻 ( 12 ) 2024年12月

出版者・発行元：Physical Review D

We derive areal inequalities for five types of attractive gravity probe surfaces, which were proposed by us in order to characterize the strength of gravity in different ways including weak gravity region, taking into account of contributions of electric and magnetic charges, angular momentum, gravitational waves, and matters. These inequalities are generalizations of the Riemannian Penrose inequality for minimal surfaces and lead to the concept of extremality for a given surface whose condition is given in terms of the gravitational mass and the electromagnetic charges. This means that the extremality is a characteristic property not only of black hole horizons or minimal surfaces but also of surfaces in weak gravity region. We also derive areal inequalities and extremality conditions for surfaces in asymptotically locally anti-de Sitter spacetimes.

DOI： 10.1103/PhysRevD.110.124051

Loosely Trapped Surface for Slowly Rotating Black Hole Open Access

Izumi K., Shiromizu T., Yoshida D., Tomikawa Y., Yoshino H.

Progress of Theoretical and Experimental Physics 2024 巻 ( 11 ) 2024年11月

出版者・発行元：Progress of Theoretical and Experimental Physics

We construct the marginal loosely trapped surface (marginal LTS) for the Kerr spacetime with a small Kerr parameter perturbatively, where the LTS condition is saturated. An LTS is a surface that specifies the strong gravity region, which is a generalization of the photon sphere in the Schwarzschild spacetime. It turns out that there are an infinite number of marginal LTSs. At the leading order of the small Kerr parameter, all of the marginal LTSs have the same area. However, one can see that the maximal marginal LTS among them is uniquely determined at the higher order.

DOI： 10.1093/ptep/ptae158

Generalization of conformal-disformal transformations of the metric in scalar-tensor theories 査読有り

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

Physical Review D 110 巻 ( 6 ) 頁： 064063 2024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：Physical Review D

We study new classes of metric transformations in the context of scalar-tensor theories, which involve both higher derivatives of the scalar field and derivatives of the metric itself. In general, such transformations are not invertible as they involve derivatives of the metric, which typically leads to instability due to Ostrogradsky ghosts. We show, however, that a certain class of this type of transformations is invertible: We construct new examples of invertible conformal (and also disformal) transformations with higher derivatives. Finally, we make use of these new transformations to construct extended mimetic theories of gravity, and we study their properties in the context of cosmology.

DOI： 10.1103/PhysRevD.110.064063

Gedanken experiments to destroy a black hole by a test particle: Multiply charged black hole with higher derivative corrections Open Access

Izumi K., Noumi T., Yoshida D.

Physical Review D 110 巻 ( 4 ) 2024年8月

出版者・発行元：Physical Review D

We investigate a gedanken experiment to destroy an extremally charged black hole by dropping a test particle, provided that there are multiple U(1) gauge fields coupled with each other through higher derivative interactions. It is known that the Coulomb repulsion prevents a test particle that would break the extremal condition from falling into an extremal black hole and therefore the black hole cannot be destroyed. We extend this observation to include higher derivative corrections. Although the extremal condition is modified by the higher derivative interactions, we find that the repulsive force induced by the higher derivative couplings is responsible for preventing a test particle that would break the modified extremal condition to reach the event horizon. Thus, we confirm that the weak cosmic censorship conjecture holds for extremally charged black holes even in the presence of higher derivative corrections, as long as the test particle approximation is justified.

DOI： 10.1103/PhysRevD.110.044008

A generalization of photon sphere based on escape/capture cone Open Access

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

European Physical Journal C 84 巻 ( 6 ) 2024年6月

出版者・発行元：European Physical Journal C

In general asymptotically flat spacetimes, bearing the null geodesics reaching the future null infinity in mind, we propose new concepts, the “dark horizons” (outer dark horizon and inner dark horizon) as generalizations of the photon sphere. They are defined in terms of the structure of escape/capture cones of photons with respect to a unit timelike vector field to capture the motion of light sources. More specifically, considering a two-sphere that represents a set of emission directions of photons, the dark horizons are located at positions where a hemisphere is marginally included in the capture and escape cones, respectively. In addition, our definition succeeds in incorporating relativistic beaming effect. We show that the dark horizon is absent in the Minkowski spacetime, while they exist in spacetimes with black hole(s) under a certain condition. We derive the general properties of the dark horizons in spherically symmetric spacetimes and explicitly calculate the locations of the dark horizons in the Vaidya spacetime and the Kerr spacetime. In particular, in the Kerr spacetime, the outer dark horizon coincides with the shadow observed from infinity on the rotation axis.

DOI： 10.1140/epjc/s10052-024-12954-9

Attractive gravity probe surface, positivity of quasi-local mass, and Arnowitt-Deser-Misner mass expression Open Access

Shiromizu, T; Izumi, K

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS 2024 巻 ( 1 ) 2024年1月

Attractive gravity probe surface with positive cosmological constant Open Access

Shiromizu, T; Izumi, K

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS 2023 巻 ( 10 ) 2023年10月

出版者・発行元：Progress of Theoretical and Experimental Physics

In 4D spacetimes with a positi v e cosmological constant, we introduce a new geometrical object associated with the cosmological horizon and then show the areal inequality. We also e xamine the attracti v e gravity probe surfaces as an indicator for the existence of attractive gravity.

DOI： 10.1093/ptep/ptad119

Boundary conditions for constraint systems in variational principle Open Access

Izumi, K; Shimada, K; Tomonari, K; Yamaguchi, M

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS 2023 巻 ( 10 ) 2023年10月

出版者・発行元：Progress of Theoretical and Experimental Physics

We show the well-posed variational principle in constraint systems. In a naive procedure of the variational principle with constraints, the proper number of boundary conditions does not match that of physical degrees of freedom, which implies that, even in theories with up to first-order derivatives, the minimal (or extremal) value of the action with the boundary terms is not a solution of the equation of motion in the Dirac procedure of constrained systems. We propose specific and concrete steps to solve this problem. These steps utilize the Hamilton formalism, which allows us to separate the physical degrees of freedom from the constraints. This reveals the physical degrees of freedom that are necessary to be fixed on boundaries, and also enables us to specify the variables to be fixed and the surface terms.

DOI： 10.1093/ptep/ptad122

その他リンク： http://arxiv.org/pdf/2303.03805v2

Asymptotic behavior of null geodesics near future null infinity. IV. Null-access theorem for generic asymptotically flat spacetime Open Access

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

PHYSICAL REVIEW D 107 巻 ( 12 ) 2023年6月

出版者・発行元：Physical Review D

In our previous papers [Phys. Rev. D 104, 064025 (2021); PRVDAQ2470-001010.1103/PhysRevD.104.064025105, 064074 (2022); PRVDAQ2470-001010.1103/PhysRevD.105.064074106, 084007 (2022)PRVDAQ2470-001010.1103/PhysRevD.106.084007], we analyzed the asymptotic behavior of future directed null geodesics near future null infinity, and then we showed a proposition on the accessibility of the null geodesics to future null infinity in a specific class of asymptotically flat spacetimes. In this paper, we adopt the retarded time of the Bondi coordinate as the parameter for the null geodesics and then see that one can relax the assumptions imposed in our previous studies. As a consequence, we obtain a new null-access theorem for generic asymptotically flat spacetimes.

DOI： 10.1103/PhysRevD.107.124050

その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevD.107.124050/fulltext

Attractive gravity probe surfaces in higher dimensions Open Access

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

Progress of Theoretical and Experimental Physics 2023 巻 ( 4 ) 2023年4月

出版者・発行元：Progress of Theoretical and Experimental Physics

A generalization of the Riemannian Penrose inequality in n-dimensional space (3 ≤ n < 8) is done. We introduce a parameter α () indicating the strength of the gravitational field, and define a refined attractive gravity probe surface (refined AGPS) with α. Then, we show the area inequality for a refined AGPS,, where A is the area of the refined AGPS, ωn - 1 is the area of the standard unit (n - 1)-sphere, G is Newton's gravitational constant, and m is the Arnowitt-Deser-Misner mass. The obtained inequality is applicable not only to surfaces in strong gravity regions such as a minimal surface (corresponding to the limit α → ∞), but also to those in weak gravity existing near infinity (corresponding to the limit).

DOI： 10.1093/ptep/ptad046

High-energy properties of the graviton scattering in quadratic gravity Open Access

Abe, Y; Inami, T; Izumi, K

JOURNAL OF HIGH ENERGY PHYSICS 2023 巻 ( 3 ) 2023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：Journal of High Energy Physics

We obtain the matter-graviton scattering amplitude in the gravitational theory of quadratic curvature, which has Rμν2 term in the action. Unitarity bound is not satisfied because of the existence of negative norm states, while an analog of unitarity bound for S-matrix unitarity holds due to the cancelation among the positive norm states and negative norm ones in the unitarity summation in the optical theorem. The violation of unitarity bound is a counter example of Llewellyn Smith’s conjecture on the relation between tree-level unitarity and renormalizability. We have recently proposed a new conjecture that an analog of the unitarity bound for S-matrix unitarity gives the equivalent conditions to those for renormalizability. We show that the gravitational theory of quadratic curvature is a nontrivial example consistent with our conjecture.

DOI： 10.1007/JHEP03(2023)213

その他リンク： https://link.springer.com/article/10.1007/JHEP03(2023)213/fulltext.html

Asymptotic behavior of null geodesics near future null infinity. III. Photons towards inward directions (vol 106, 084007, 2022) Open Access

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

PHYSICAL REVIEW D 107 巻 ( 2 ) 2023年1月

Asymptotic behavior of null geodesics near future null infinity: Significance of gravitational waves (vol 104, 064025, 2021) Open Access

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

PHYSICAL REVIEW D 107 巻 ( 2 ) 2023年1月

Maximum size of black holes in our accelerating Universe Open Access

Shiromizu, T; Izumi, K; Lee, K; Soligon, D

PHYSICAL REVIEW D 106 巻 ( 8 ) 2022年10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：Physical Review D

In accordance with current models of the accelerating Universe as a spacetime with a positive cosmological constant, new results about a cosmological upper bound for the area of stable marginally outer trapped surfaces are found taking into account angular momentum, gravitational waves, and matter. Compared to previous results which take into account only some of the aforementioned variables, the bound is found to be tighter, giving a concrete limit to the size of black holes especially relevant in the early Universe.

DOI： 10.1103/PhysRevD.106.084014

Asymptotic behavior of null geodesics near future null infinity. III. Photons towards inward directions 査読有り

PHYSICAL REVIEW D 106 巻 2022年10月

Asymptotic behavior of null geodesics near future null infinity. III. Photons towards inward directions

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

PHYSICAL REVIEW D 106 巻 ( 8 ) 2022年10月

掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Review D

A new sufficient condition for photons emitted near future null infinity to reach future null infinity is derived by studying null geodesics in the Bondi coordinates in asymptotically flat spacetimes. In our previous works [M. Amo, Phys. Rev. D 104, 064025 (2021).PRVDAQ2470-001010.1103/PhysRevD.104.064025; M. Amo, Phys. Rev. D 105, 064074 (2022).PRVDAQ2470-001010.1103/PhysRevD.105.064074], such a condition was established for photons emitted in outward or tangential directions to constant radial surfaces. This paper improves our previous result by including photons emitted in inward directions. In four dimensions, imposing the same assumptions on the metric functions as previously, we prove that photons reach future null infinity if their initial values of |dr/du| are smaller than a certain quantity, where r and u are the radial and retarded time coordinates, respectively. This quantity is determined by the asymptotic properties of the metric and is connected to the conjectured maximal luminosity. In higher dimensions, photons emitted with dr/du>-(1-1/3)≈-0.423 are shown to reach future null infinity without the assumptions on the metric functions.

DOI： 10.1103/PhysRevD.106.084007

Brane dynamics of holographic BCFTs Open Access

Izumi, K; Shiromizu, T; Suzuki, K; Takayanagi, T; Tanahashi, N

JOURNAL OF HIGH ENERGY PHYSICS 2022 巻 ( 10 ) 2022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：Journal of High Energy Physics

In this paper we study various dynamical aspects of the AdS/BCFT correspondence in higher dimensions. We study properties of holographic stress energy tensor by analyzing the metric perturbation in the gravity dual. We also calculate the stress energy tensor for a locally excited state on a half plane in a free scalar CFT. Both of them satisfy a reflective boundary condition that is expected for any BCFTs. We also study the behavior of the scalar field perturbation in the AdS/BCFT setup and show that they also show complete reflections. Moreover, we find that the entanglement entropy of a BCFT computed from the AdS/BCFT matched with that calculated from the Island formula, which supports the Island/BCFT correspondence in higher dimensions. Finally we show how we can calculate one point functions in a BCFT in our gravity dual.

DOI： 10.1007/JHEP10(2022)050

Four types of attractive gravity probe surfaces Open Access

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

PHYSICAL REVIEW D 106 巻 ( 6 ) 2022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 reexamine the concept of the attractive gravity probe surface recently proposed as an indicator for strength of gravity. Then, we propose three new variant concepts and show refined inequalities for the four types of the attractive gravity probe surfaces by taking account of the angular momentum, gravitational waves, and matter.

DOI： 10.1103/PhysRevD.106.064028

Asymptotic behavior of null geodesics near future null infinity. II. Curvatures, photon surface, and dynamically transversely trapping surface

Amo Masaya, Shiromizu Tetsuya, Izumi Keisuke, Yoshino Hirotaka, Tomikawa Yoshimune

PHYSICAL REVIEW D 105 巻 ( 6 ) 2022年3月

Refined inequalities for a loosely trapped surface and attractive gravity probe surface Open Access

Lee, K; Shiromizu, T; Izumi, K

PHYSICAL REVIEW D 105 巻 ( 4 ) 2022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：Physical Review D

We reexamine a loosely trapped surface proposed as an indicator for strong gravity and an attractive gravity probe surface as that for gravity. Refined inequalities for them are derived by taking account of angular momentum, gravitational waves, and matters.

DOI： 10.1103/PhysRevD.105.044037

その他リンク： http://arxiv.org/pdf/2111.08237v1

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