125 citations · 1.5k across the 62 of their papers we have counts for
62 papers
Attractive gravity probe surface with positive cosmological constant
Tetsuya Shiromizu, Keisuke Izumi
In four dimensional spacetimes with a positive cosmological constant, we introduce a new geometrical object associated with the cosmological horizon and then show the areal inequal…
Asymptotic behavior of null geodesics near future null infinity IV: Null-access theorem for generic asymptotically flat spacetime
Masaya Amo, Keisuke Izumi, Yoshimune Tomikawa +2
In our previous papers [arXiv:2106.03150, arXiv:2110.10917, arXiv:2208.00822], we analyzed the asymptotic behavior of future directed null geodesics near future null infinity and t…
A generalization of photon sphere based on escape/capture cone
Masaya Amo, Keisuke Izumi, Hirotaka Yoshino +2
In asymptotically flat spacetimes, bearing the null geodesics reaching the future null infinity in mind, we propose new concepts, the "dark horizons" as generalizations of the phot…
Boundary Conditions for Constraint Systems in Variational Principle
Keisuke Izumi, Keigo Shimada, Kyosuke Tomonari +1
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 doe…
High-energy properties of the graviton scattering in quadratic gravity
Yugo Abe, Takeo Inami, Keisuke Izumi
We obtain the matter-graviton scattering amplitude in the gravitational theory of quadratic curvature, which has term in the action. Unitarity bound is not satisfied bec…
Attractive gravity probe surfaces in higher dimensions
Keisuke Izumi, Yoshimune Tomikawa, Tetsuya Shiromizu +1
A generalization of the Riemannian Penrose inequality in -dimensional space () is done. We introduce a parameter () indicating the streng…