Masa-Aki Sakagami

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We present a first physical application of Tsallis’ generalized entropy to the thermodynamics of self-gravitating systems. The stellar system confined in a spherical cavity of radius re exhibits an instability, so-called gravothermal catastrophe, which has been originally investigated by Antonov (Vest.Leningrad Gros.Univ. 7 (1962) 135) and Lynden-Bell &(More)
We construct a phenomenological conformal field theory (CFT) model of the threedimensional Hawking-Page transition. We find that free fermion CFT models on the boundary torus give a description of the three-dimensional Hawking-Page transition. If modular invariance is respected, the free fermion model implies that the transition occurs continuously through(More)
With particular attention to the recently postulated introduction of a nonextensive generalization of Boltzmann-Gibbs statistics, we study the long-term stellar dynamical evolution of self-gravitating systems on time scales much longer than the two-body relaxation time. In a self-gravitating N-body system confined in an adiabatic wall, we show that the(More)
We revisit the issues on the thermodynamic property of stellar self-gravitating system arising from Tsallis’ non-extensive entropy. Previous papers (Physica A 307 (2002) 185; ibid. (2003) in press (cond-mat/0204315)) have revealed that the extremum-state of Tsallis entropy, so-called stellar polytrope, has consistent thermodynamic structure, which predicts(More)
We propose a measurement method for the mean speed distribution of collective motions of highly dense groups with optical flow in this paper. This measurement is fundamental for ecological investigations and mathematical modeling of collective animal behaviors, including human crowds. Our method is applicable to highly dense homogeneous groups wherein(More)
Atsushi Nishizawa,* Seiji Kawamura, Tomotada Akutsu, Koji Arai, Kazuhiro Yamamoto, Daisuke Tatsumi, Erina Nishida, Masa-aki Sakagami, Takeshi Chiba, Ryuichi Takahashi, and Naoshi Sugiyama Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan TAMA Project, National Astronomical Observatory of Japan, Mitaka, Tokyo(More)
In this paper, we continue to investigate the thermodynamic properties of stellar self-gravitating system arising from the Tsallis generalized entropy. In particular, physical interpretation of the thermodynamic instability, as has been revealed by previous paper(Taruya & Sakagami, Physica A 307 (2002) 185), is discussed in detail based on the framework of(More)
We present a first physical application of Tsallis’ generalized entropy to the thermodynamics of self-gravitating systems. The stellar system confined in a spherical cavity of radius re exhibits an instability, so-called gravothermal catastrophe, which has been originally investigated by Antonov (Vest.Leningrad Gros.Univ. 7 (1962) 135) and Lynden-Bell &(More)
We propose a visual tracking method with an NACA airfoil model for dense fish schools in which occlusions occur frequently. Although much progress has been made for tracking multiple objects, it remains a challenging task to track individuals due to factors such as occlusion and target appearance variation. In this paper, we first introduce a NACA airfoil(More)