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Search Results: 1 - 10 of 3330 matches for " Hikaru Yamamoto "
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Weighted Hamiltonian stationary Lagrangian submanifolds and generalized Lagrangian mean curvature flows in toric almost Calabi-Yau manifolds
Hikaru Yamamoto
Mathematics , 2013,
Abstract: In this paper we generalize examples of Hamiltonian stationary Lagrangian submanifolds constructed by Lee and Wang in $\mathbb{C}^m$ to toric almost Calabi-Yau manifolds. We construct examples of weighted Hamiltonian stationary Lagrangian submanifolds in toric almost Calabi-Yau manifolds and solutions of generalized Lagrangian mean curvature flows starting from these examples. We allow these flows to have some singularities and topological changes.
Ricci-mean curvature flows in gradient shrinking Ricci solitons
Hikaru Yamamoto
Mathematics , 2015,
Abstract: Huisken studied asymptotic behavior of a mean curvature flow in a Euclidean space when it develops a singularity of type I, and proved that its rescaled flow converges to a self-shrinker in the Euclidean space. In this paper, we generalize this result for a Ricci-mean curvature flow moving along a Ricci flow constructed from a gradient shrinking Ricci soliton.
Lagrangian self-similar solutions in gradient shrinking K?hler-Ricci solitons
Hikaru Yamamoto
Mathematics , 2015,
Abstract: In this paper, we give a lower bound estimate for the diameter of a Lagrangian self-shrinker in a gradient shrinking K\"ahler-Ricci soliton as an analog of a result of A. Futaki, H. Li and X.-D. Li for a self-shrinker in a Euclidean space. We also prove an analog of a result of H.-D. Cao and H. Li about the non-existence of compact self-expanders in a Euclidean space.
Special Lagrangians and Lagrangian self-similar solutions in cones over toric Sasaki manifolds
Hikaru Yamamoto
Mathematics , 2012,
Abstract: We construct some examples of special Lagrangian submanifolds and Lagrangian self-similar solutions in almost Calabi-Yau cones over toric Sasaki manifolds. For example, for any integer g>0, we can construct a real 6 dimensional Calabi-Yau cone M_g and a 3 dimensional special Lagrangian submanifold L^1_g in M_g which is diffeomorphic to the product of a closed surface of genus g and the real line R, and a 3 dimensional compact Lagrangian self-shrinker L^2_g in M_g which is diffeomorphic to the product of the closed surface of genus g and a circle S^1.
Vortex-induced topological transition of the bilinear-biquadratic Heisenberg antiferromagnet on the triangular lattice
Hikaru Kawamura,Atsushi Yamamoto
Physics , 2007, DOI: 10.1143/JPSJ.76.073704
Abstract: The ordering of the classical Heisenberg antiferromagnet on the triangular lattice with the the bilinear-biquadratic interaction is studied by Monte Carlo simulations. It is shown that the model exhibits a topological phase transition at a finite-temperature driven by topologically stable vortices, while the spin correlation length remains finite even at and below the transition point. The relevant vortices could be of three different types, depending on the value of the biquadratic coupling. Implications to recent experiments on the triangular antiferromagnet NiGa$_2$S$_4$ is discussed.
Simulation study of the inhomogeneous Olami-Feder-Christensen model of earthquakes
Takumi Yamamoto,Hajime Yoshino,Hikaru Kawamura
Physics , 2010, DOI: 10.1140/epjb/e2010-10503-4
Abstract: Statistical properties of the inhomogeneous version of the Olami-Feder-Christensen (OFC) model of earthquakes is investigated by numerical simulations. The spatial inhomogeneity is assumed to be dynamical. Critical features found in the original homogeneous OFC model, e.g., the Gutenberg-Richter law and the Omori law are often weakened or suppressed in the presence of inhomogeneity, whereas the characteristic features found in the original homogeneous OFC model, e.g., the near-periodic recurrence of large events and the asperity-like phenomena persist.
Z_2-vortex ordering of the triangular-lattice Heisenberg antiferromagnet
Hikaru Kawamura,Atsushi Yamamoto,Tsuyoshi Okubo
Physics , 2009, DOI: 10.1143/JPSJ.79.023701
Abstract: Ordering of the classical Heisenberg antiferromagnet on the triangular lattice is studied by means of a mean-field calculation, a scaling argument and a Monte Carlo simulation, with special attention to its vortex degree of freedom. The model exhibits a thermodynamic transition driven by the Z_2-vortex binding-unbinding, at which various thermodynamic quantities exhibit an essential singularity. The low-temperature state is a "spin-gel" state with a long but finite spin correlation length where the ergodicity is broken topologically. Implications to recent experiments on triangular-lattice Heisenberg antiferromagnets are discussed.
Self-similar solutions to the mean curvature flows on Riemannian cone manifolds and special Lagrangians on toric Calabi-Yau cones
Akito Futaki,Kota Hattori,Hikaru Yamamoto
Mathematics , 2011,
Abstract: The self-similar solutions to the mean curvature flows have been defined and studied on the Euclidean space. In this paper we initiate a general treatment of the self-similar solutions to the mean curvature flows on Riemannian cone manifolds. As a typical result we extend the well-known result of Huisken about the asymptotic behavior for the singularities of the mean curvature flows. We also extend the results on special Lagrangian submanifolds on $\mathbb C^n$ to the toric Calabi-Yau cones over Sasaki-Einstein manifolds.
Asperity characteristics of the Olami-Feder-Christensen model of earthquakes
Hikaru Kawamura,Takumi Yamamoto,Takeshi Kotani,Hajime Yoshino
Physics , 2009, DOI: 10.1103/PhysRevE.81.031119
Abstract: Properties of the Olami-Feder-Christensen (OFC) model of earthquakes are studied by numerical simulations. The previous study indicated that the model exhibits ``asperity''-like phenomena, {\it i.e.}, the same region ruptures many times near periodically [T.Kotani {\it et al}, Phys. Rev. E {\bf 77}, 010102 (2008)]. Such periodic or characteristic features apparently coexist with power-law-like critical features, {\it e.g.}, the Gutenberg-Richter law observed in the size distribution. In order to clarify the origin and the nature of the asperity-like phenomena, we investigate here the properties of the OFC model with emphasis on its stress distribution. It is found that the asperity formation is accompanied by self-organization of the highly concentrated stress state. Such stress organization naturally provides the mechanism underlying our observation that a series of asperity events repeat with a common epicenter site and with a common period solely determined by the transmission parameter of the model. Asperity events tend to cluster both in time and in space.
Nucleation process in the Burridge-Knopoff model of earthquakes
Yushi Ueda,Shouji Morimoto,Shingo Kakui,Takumi Yamamoto,Hikaru Kawamura
Physics , 2014, DOI: 10.1209/0295-5075/106/69001
Abstract: Nucleation process of the one-dimensional Burridge-Knopoff model of earthquakes obeying the rate- and state-dependent friction law is studied both analytically and numerically. The properties of the nucleation dynamics, the nucleation lengths and the duration times are examined together with their continuum limits.
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