著者

Yasutake Nobutoshi Hashimoto Masa-aki Eriguchi Yoshiharu Department of Physics Kyushu University Department of Physics Kyushu University Department of Earth Science and Astronomy Graduate School of Arts and Sciences University of Tokyo

出版者

Published for the Yukawa Institute for Theoretical Physics and the Physical Society of Japan

雑誌

Progress of theoretical physics (ISSN:0033068X)

巻号頁・発行日

vol.113, no.5, pp.953-962, 2005-05-25

参考文献数

45

被引用文献数

17

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We present a scenario for the formation of strange stars due to spin-down of rapidly rotating neutron stars left after supernova explosions. In this scenario the rapid rotation plays a crucial role. We assume that the total baryon mass is conserved but that both total energy and angular momentum are lost due to emission of gravitational waves and/or magnetic braking. Under this assumption, we calculate the transition from rapidly rotating neutron stars to slowly rotating strange stars. As a result, we find that a large amount of energy, ~10^<53>, ergs is released. The liberated energy might become a new energy source for the delayed explosion of a supernova. Furthermore, our scenario suggests that supernovas associated with gamma-ray bursts are feasible sources of observable gravitational waves.

著者

Hawley John F. De Villiers Jean-Pierre

出版者

Published for the Yukawa Institute for Theoretical Physics and the Physical Society of Japan

雑誌

Progress of theoretical physics. Supplement (ISSN:03759687)

巻号頁・発行日

no.155, pp.132-139, 2004-11-15

参考文献数

21

被引用文献数

4

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Observations are providing increasingly detailed quantitative information about the accretion flows that power such high energy systems as X-ray binaries and active galactic nuclei. Analytic models of such systems must rely on assumptions such as regular flow geometry and a simple, parameterized stress. Global numerical simulations offer a way to investigate the basic physical dynamics of accretion flows without these assumptions. For black hole accretion studies one solves the equations of general relativistic magnetohydro-dynamics. Magnetic fields are of fundamental importance to the structure and evolution of accretion disks because magnetic turbulence is the source of the anomalous stress that drives accretion. We have developed a three-dimensional general relativistic magnetohydrodynamic simulation code to evolve time-dependent accretion systems self-consistently. Recent global simulations of black hole accretion disks suggest that the generic structure of the accretion flow is usefully divided into five regimes : the main disk, the inner disk, the corona, the evacuated funnel, and the funnel wall jet. The properties of each of these regions are summarized.

著者

Mizuno Tsunefumi Miyawaki Ryohei Ebisawa Ken KUBOTA Aya MIYAMOTO Masao WINTER Lisa UEDA Yoshihiro ISOBE Naoki MAKISHIMA Kazuo

出版者

Published for the Yukawa Institute for Theoretical Physics and the Physical Society of Japan

雑誌

Progress of theoretical physics. Supplement (ISSN:03759687)

巻号頁・発行日

no.169, pp.229-233, 2007-12-19

参考文献数

24

被引用文献数

1

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We report about the Suzaku observation of two ultraluminous X-ray sources (ULXs), X-1 and X-2, in NGC1313, together with their spectra by XMM-Newton. During the observation, both showed intensity-correlated spectral changes. The brighter source, X-1, exhibited the highest luminosity (~3×10^<40>erg s^<-1>) ever recorded from this source. Its spectral variation is ascribed to a strong power-law like component with a mild high energy curvature, while about 10% of the flux is carried by a stable soft component modeled by a cool disk emission. These properties suggest that the source was in the "very high" state, wherein the disk emission is strongly Comptonized and the optically-thick disk is truncated at a large radii or cooled off. The spectrum of X-2 is best represented, in its fainter phase, by a multicolor disk model with the innermost disk temperature of 1.2-1.3keV, and becomes flatter as the source gets brighter. Hence X-2 is interpreted to be in a slim disk state. These results suggest that the two ULXs host black holes of a few tens to a few hundreds solar masses.

著者

Toki Hiroshi

出版者

Published for the Yukawa Institute for Theoretical Physics and the Physical Society of Japan

雑誌

Progress of theoretical physics. Supplement (ISSN:03759687)

巻号頁・発行日

no.168, pp.602-609, 2007

参考文献数

9

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We study the role of pion for the structure of finite nuclei. We take the chiral sigma model, where the pions are the Nambu-Goldstone bosons of chiral symmetry breaking. We then take the finite pion mean field in the relativistic mean field approximation. We study first the nuclei in the range of A=36 to A=64 with equal number of neutrons and protons. We find that the magic number gap at N = Z = 28 appears due to the finite pion mean field effect. The pion provides a large spin-orbit splitting effect due to a mechanism totally different from the ordinary spin-orbit term of the relativistic origin. On the other hand, we are not able to shift the magic number appearing at A=36 instead of A=40, which is now a motivation to work out the parity and charge projection. The standard projection technique provides an integro-differential equation for the Dirac equation. As an example, we work out ^4He in the relativistic chiral mean field model. We find good properties for the ground state energy and the size and the pion energy contribution. The form factor also comes out to be quite satisfactory. We then switch to the non-relativistic method to describe the large tensor correlations in terms of the tensor optimized shell model (TOSM). We describe ^4He and ^9Li in TOSM where the tensor force is treated fully by taking enough configuration space. We show important consequenses of the tensor correlations caused by the tensor interaction due to the Pauli blocking effect on the phase shifts of neutron scattering from ^4He and the halo structure of ^<11>Li.

著者

Suetani Hiromichi Iba Yukito Aihara Kazuyuki

出版者

Published for the Yukawa Institute for Theoretical Physics and the Physical Society of Japan

雑誌

Progress of theoretical physics. Supplement (ISSN:03759687)

巻号頁・発行日

no.161, pp.340-343, 2006-04-20

参考文献数

11

被引用文献数

1

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An approach based on the kernel methods for capturing the nonlinear interdependence between two signals is introduced. It is demonstrated that the proposed approach is useful for characterizing generalized synchronization with a successful simple example. An attempt to choose an optimal kernel parameter based on cross validation is also discussed.