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Search Results: 1 - 10 of 1431 matches for " Yasuhiro Takayanagi "
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Luminescence of a Cooper Pair
Yasuhiro Asano,Ikuo Suemune,Hideaki Takayanagi,Eiichi Hanamura
Physics , 2009, DOI: 10.1103/PhysRevLett.103.187001
Abstract: This paper theoretically discusses the photon emission spectra of a superconducting pn-junction. On the basis of the second order perturbation theory for electron-photon interaction, we show that the recombination of a Cooper with two p-type carriers causes drastic enhancement of the luminescence intensity. The calculated results of photon emission spectra explain characteristic features of observed signal in an recent experiment. Our results indicate high functionalities of superconducting light-emitting devices.
Spin-Density-Wave Gap with Dirac Nodes and Two-Magnon Raman Scattering in BaFe2As2
Shunji Sugai,Yuki Mizuno,Ryoutarou Watanabe,Takahiko Kawaguchi,Koshi Takenaka,Hiroshi Ikuta,Yasumasa Takayanagi,Naoki Hayamizu,Yasuhiro Sone
Physics , 2012, DOI: 10.1143/JPSJ.81.024718
Abstract: Raman selection rules for electronic and magnetic excitations in BaFe2As2 were theoretically investigated and applied them to the separate detection of the nodal and anti-nodal gap excitations at the spin density wave (SDW) transition and the separate detection of the nearest and the next nearest neighbor exchange interaction energies. The SDW gap has Dirac nodes, because many orbitals participate in the electronic states near the Fermi energy. Using a two-orbital band model the electronic excitations near the Dirac node and the anti-node are found to have different symmetries. Applying the symmetry difference to Raman scattering the nodal and anti-nodal electronic excitations are separately obtained. The low-energy spectra from the anti-nodal region have critical fluctuation just above TSDW and change into the gap structure by the first order transition at TSDW, while those from the nodal region gradually change into the SDW state. The selection rule for two-magnon scattering from the stripe spin structure was obtained. Applying it to the two-magnon Raman spectra it is found that the magnetic exchange interaction energies are not presented by the short-range superexchange model, but the second derivative of the total energy of the stripe spin structure with respect to the moment directions. The selection rule and the peak energy are expressed by the two-magnon scattering process in an insulator, but the large spectral weight above twice the maximum spin wave energy is difficult to explain by the decayed spin wave. It may be explained by the electronic scattering of itinerant carriers with the magnetic self-energy in the localized spin picture or the particle-hole excitation model in the itinerant spin picture. The magnetic scattering spectra are compared to the insulating and metallic cuprate superconductors whose spins are believed to be localized.
Notes on Giant Gravitons on PP-waves
Hiromitsu Takayanagi,Tadashi Takayanagi
Physics , 2002, DOI: 10.1088/1126-6708/2002/12/018
Abstract: We investigate the giant gravitons in the maximally supersymmetric IIB pp-wave from several viewpoints: (i) the dynamics of D3-branes, (ii) the world-sheet description and (iii) the correlation functions in the dual N=4 Yang-Mills theory. In particular, we derive the BPS equation of a D3-brane with magnetic flux, which is equivalent to multiple D-strings, and discuss the behavior of solutions in the presence of RR-flux. We find solutions which represent the excitations of the giant gravitons in that system.
Open Strings in Exactly Solvable Model of Curved Spacetime and PP-Wave Limit
Hiromitsu Takayanagi,Tadashi Takayanagi
Physics , 2002, DOI: 10.1088/1126-6708/2002/05/012
Abstract: In this paper we study the superstring version of the exactly solvable string model constructed by Russo and Tseytlin. This model represents superstring theory in a curved spacetime and can be seen as a generalization of the Melvin background. We investigate D-branes in this model as probes of the background geometry by constructing the boundary states. We find that spacetime singularities in the model become smooth at high energy from the viewpoint of open string. We show that there always exist bulk (movable) D-branes by the effect of electric flux. The model also includes Nappi-Witten model as the Penrose limit and supersymmetry is enhanced in the limit. We examine this phenomenon in the open string spectrum. We also find the similar enhancement of supersymmetry can be occurred in several coset models.
Overview of osteoimmunology: What's happened? And what's going on?
Hiroshi Takayanagi
Arthritis Research & Therapy , 2012, DOI: 10.1186/ar3567
Why Japanese Aid is Ineffective in Reducing Poverty
Akio Takayanagi
Kasarinlan : Philippine Journal of Third World Studies , 1990,
Abstract: Japan is expected to become the largest donor of ODA (Official Development Assistance) in the world, due to the rapid increase of its ODA budget in recent years, high yen rate, and decrease in the ODA of the United States, erstwhile the biggest aid donor. The quality, however, of Japan's ODA has come under fire: the proportion of grants to loans is low; its beneficiaries are said to be Japanese corporations; and instead of helping the poor in the Third World, it has contributed to socio-cultural problems and environmental destruction. This paper discusses the allocation of ODA, Japan's policy on aid, the implementation of ODA, and recent trends.
Augmentation Mammaplasty Using Implants: A Review
Susumu Takayanagi
Archives of Plastic Surgery , 2012, DOI: http://dx.doi.org/10.5999/aps.2012.39.5.448
Abstract: One of the techniques for augmentation mammaplasty is the procedure using implants. Eventhough this technique has been used for many years, there are still several controversial issuesto be discussed and overcome for patient safety. In this review article, capsular contracture,leak or rupture of the implants, possible systemic disease, relation with breast cancer, andrecent problems with Poly Implant Prothese implants are described and discussed.
Prevention of Adiposity by the Oral Administration of β-Cryptoxanthin
Katsuhiko Takayanagi
Frontiers in Neurology , 2011, DOI: 10.3389/fneur.2011.00067
Abstract: β-Cryptoxanthin (β-CRX) is a carotenoid found in human blood. It is specifically rich in Satsuma mandarin (Citrus unshiu Marc.) but very little in other fruits or vegetables. Several reports indicate the health promoting benefits of β-CRX. As we had reported visceral fat reduction on mildly obese male by the oral administration of β-CRX, a detailed mechanism has not been identified. To identify the mechanism, obese model mouse, TSOD was used in the present study. Oral administration of β-CRX repressed body weight, abdominal adipose tissue weight, and serum lipid concentrations on TSOD mice. The outstanding observation is the significant repression of adipocyte hypertrophy. DNA microarray analysis strongly indicates that the oral administration of β-CRX represses the inflammatory cytokine secretion and improves the lipid metabolism and the energy consumption. It also suggests these effects are partly mediated by PPAR-α, not only lipid metabolism and adipocyte differentiation control but possibly internal circadian clock modulation.
Entanglement Entropy from a Holographic Viewpoint
Tadashi Takayanagi
Physics , 2012, DOI: 10.1088/0264-9381/29/15/153001
Abstract: The entanglement entropy has been historically studied by many authors in order to obtain quantum mechanical interpretations of the gravitational entropy. The discovery of AdS/CFT correspondence leads to the idea of holographic entanglement entropy, which is a clear solution to this important problem in gravity. In this article, we would like to give a quick survey of recent progresses on the holographic entanglement entropy. We focus on its gravitational aspects, so that it is comprehensible to those who are familiar with general relativity and basics of quantum field theory.
Modular Invariance of Strings on PP-Waves with RR-flux
Tadashi Takayanagi
Physics , 2002, DOI: 10.1088/1126-6708/2002/12/022
Abstract: We study the modular invariance of strings on pp-waves with RR-flux. We explicitly show that the one-loop partition functions of the maximally supersymmetric pp-waves and their orbifolds can be modular invariant in spite of the mass terms in the light-cone gauge. From this viewpoint, we also determine the spectrum of type 0B theory on pp-wave and discuss its gauge theory dual. Furthermore, we investigate the spectrum of a non-supersymmetric orbifold and point out its supersymmetry enhancement in the Penrose limit.
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