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Search Results: 1 - 10 of 2376 matches for " Hiroaki Nakano "
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Scalar Mass and Cosmological Constant induced by ``Anomalous" $U(1)$ $D$-term
Hiroaki Nakano
Physics , 1994,
Abstract: When the supersymmetric theory contains the ``anomalous" $U(1)$ gauge symmetry with Green-Schwarz anomaly cancellation mechanism in 4 dimensions, its Fayet-Iliopoulos $D$-term generates non-universal scalar masses and the positive cosmological constant after the supersymmetry breaking. Both give the new contributions to the known results from $F$-term. Our mechanism is naturally realized in many string models and in some cases, leads to remarkable cancellations between $F$- and $D$-term contributions, providing the universal scalar mass and vanishing cosmological constant. We illustrate how such a possibility can arise by taking a simple orbifold example.
Improving the Effective Potential, Multi-Mass Problem and Modified Mass-Dependent Scheme
Hiroaki Nakano,Yusuke Yoshida
Physics , 1993, DOI: 10.1103/PhysRevD.49.5393
Abstract: We present a new procedure for improving the effective potential by using renormalization group equation (RGE) in the presence of several mass scales. We propose a modification of the mass-dependent (MD) renormalization scheme, MDbar scheme, so that the scalar mass parameter runs at most logarithmically on the one hand and the decoupling of heavy particles is naturally incorporated in the RGE's on the other. Thanks to these properties, the procedure in MDbar scheme turns out to be very simple compared with the regionwise procedure in MSbar scheme proposed previously. The relation with other schemes is also discussed both analytically and numerically.
"Anomalous" U(1) Symmetry in Orbifold String Models
Tatsuo Kobayashi,Hiroaki Nakano
Physics , 1996, DOI: 10.1016/S0550-3213(97)00210-1
Abstract: ``Anomalous'' U(1) gauge symmetry with Green-Schwarz anomaly cancellation mechanism is discussed in the orbifold construction of four-dimensional heterotic string models. Some conditions are given as criteria to have ``anomalous'' U(1) in orbifold string models. In particular, ``anomalous'' U(1) is absent if the massless twisted matter has no mixing between visible and hidden sectors or if a certain type of discrete symmetries are found. We then give a general procedure for classifying orbifold models with ``anomalous'' U(1) and for identifying the ``anomalous'' U(1) basis. We illustrate our procedure in Z_3 and Z_4 orbifold models. According to our procedure, the classification of ``anomalous'' U(1) can be reduced to the classification in the absence of a Wilson line. We also discuss discrete symmetries left unbroken after the ``anomalous'' U(1) breaking. This includes a possible relation between ``anomalous'' U(1) and discrete R-symmetries.
Impact of Rotavirus Vaccination in Severe Rotavirus Gastroenteritis Outpatient Visits at Three Pediatric Primary Care Clinics in Shibata City, Niigata Prefecture, Japan  [PDF]
Tomohiro Oishi, Shinya Tsukano, Tokushi Nakano, Shoji Sudo, Hiroaki Kuwajima
Open Journal of Pediatrics (OJPed) , 2014, DOI: 10.4236/ojped.2014.44040
Abstract: The impact of rotavirus (RV) vaccination in reducing severe rotavirus gastroenteritis (RVGE) in outpatient settings was prospectively surveyed in three pediatric clinics in Shibata City. In children younger than 3 years of age, the occurrence of severe RVGE among all acute gastroenteritis (AGE) was found to be significantly lower in three seasons after introduction of RV vaccines, compared to that in 2011, before introduction of RV vaccines. The incidence rates of severe RVGE among children younger than 3 years of age were found to be reduced by 71.2%, 47.7%, and 81.1% for 2012, 2013, and 2014, respectively, compared to that in 2011. These results suggest that the RV vaccination is effective for the prevention of severe RVGE in Japanese voluntary RV vaccination settings with estimated coverage rates of 32.5%, 40.5% and 47.1% for 2012, 2013 and 2014, respectively. It is expected that the reducing effect on severe RVGE would be persistently established by increasing the vaccine coverage rates.
Yukawa Hierarchy Transfer from Superconformal Sector and Degenerate Sfermion Masses
Tatsuo Kobayashi,Hiroaki Nakano,Haruhiko Terao
Physics , 2001, DOI: 10.1103/PhysRevD.65.015006
Abstract: We propose a new type of supersymmetric models coupled to superconformal field theories (SCFT's), leading simultaneously to hierarchical Yukawa couplings and completely degenerate sfermion masses. We consider models with an extra Abelian gauge symmetry to generate hierarchical structure for couplings between the SM sector and the SC sector. Interestingly, this hierarchy is inversely transferred to the Yukawa couplings in the SM sector. In this type of models, flavor-independent structure of the superconformal fixed point guarantees that the sfermion masses of the first and the second generations are completely degenerate at low energy.
Stress-Corrosion Cracking Property of Aluminum-Magnesium Alloy Processed by Equal-Channel Angular Pressing
Hiroaki Nakano,Satoshi Oue,Seiji Taguchi,Shigeo Kobayashi,Zenji Horita
International Journal of Corrosion , 2012, DOI: 10.1155/2012/543212
Abstract: Stress-corrosion cracking property of an aluminum-magnesium alloy processed by equal-channel angular pressing (ECAP) was investigated by a slow strain-rate tensile technique in a 3% NaCl solution of pH?4.2 at 303?K. The maximum stress and elongation of the Al-Mg alloy were lower in the NaCl solution than in air. The stress-corrosion cracking property was evaluated by the decrease ratio of maximum stress and elongation of the Al-Mg alloy with NaCl solution, and , respectively. and were lower with ECAP than without it, showing that the susceptibility of stress-corrosion cracking decreased with ECAP. The polarization curve and time dependence of the anodic current density at constant potential of the Al-Mg alloy in the NaCl solution revealed that the anodic current density was lower with ECAP than without it, or the corrosion resistance of the Al-Mg alloy was improved by ECAP. The decrease in stress-corrosion crack susceptibility of the Al-Mg alloy with ECAP is attributed to an improvement in corrosion resistance afforded by ECAP. 1. Introduction Although aluminum is an inherently active metal, it shows excellent corrosion resistance over a neutral range of pH 4–8 owing to its superficial oxide film. However, in solutions containing Cl?, pitting corrosion occurs locally where the oxide film is attacked by Cl? [1, 2]. When additional stress is applied, stress-corrosion cracking also occurs along the crystal grain boundary, resulting in serious damage [3–5]. On the other hand, reducing the grain size of metallic materials to the submicrometer or even the nanometer range by equal-channel angular pressing (ECAP), high-pressure torsion (HPT), or a severe torsion-straining process (STSP) is being studied increasingly with the aim of improving mechanical properties such as strength and ductility [6–11]. The effect of severe plastic deformation on the pitting corrosion resistance of Al alloys has been reported [12–15]; however, reports on the effect of stress-corrosion cracking are rare. In this study, the stress-corrosion cracking property of an alloy of Al-3%Mg (by mass) processed by ECAP was investigated. Stress-corrosion cracking property was evaluated by a slow strain-rate tensile technique in a 3% NaCl solution. Since the stress-corrosion cracking property of the Al-Mg alloy was expected to depend on corrosion resistance, the effect of ECAP on the corrosion resistance of the Al-Mg alloy was investigated by polarization curves and the anodic current density at constant potential in the NaCl solution. The fracture area after the slow strain-rate tensile test
Quark condensate in nuclear matter based on Nuclear Schwinger-Dyson formalism
Tomohiro Mitsumori,Nobuo Noda,Hiroaki Kouno,Akira Hasegawa,Masahiro Nakano
Physics , 1996, DOI: 10.1103/PhysRevC.55.1577
Abstract: The effects of higher order corrections of ring diagrams for the quark condensate are studied by using the bare vertex Nuclear Schwinger Dyson formalism based on $\sigma$-$\omega$ model. At the high density the quark condensate is reduced by the higher order contribution of ring diagrams more than the mean field theory or the Hartree-Fock .
Improving the Effective Potential
Masako Bando,Taichiro Kugo,Nobuhiro Maekawa,Hiroaki Nakano
Physics , 1992, DOI: 10.1016/0370-2693(93)90725-W
Abstract: A general procedure is presented how to improve the effective potential by using the renormalization group equation (RGE) in MS bar scheme. If one knows the L-loop effective potential and the RGE coefficient functions up to (L+1)-loop level, this procedure gives an improved potential which satisfies the RGE and contains all of the leading, next-to-leading,... , and L-th-to-leading log terms.
Improving the Effective Potential:Multi-Mass-Scale Case
Masako Bando,Taichiro Kugo,Nobuhiro Maekawa,Hiroaki Nakano
Physics , 1992, DOI: 10.1143/PTP.90.405
Abstract: Previously proposed procedure for improving the effective potential by using renormalization group equation (RGE) is generalized so as to be applicable to any system containing several different mass scales. If one knows L-loop effective potential and (L+1)-loop RGE coefficient functions, this procedure gives an improved potential which satisfies the RGE and contains all of the leading, next-to-leading,..., and L-th-to-leading log terms. Our procedure here also clarifies how naturally the so-called effective field theory can be incorporated in the RGE in MS bar scheme.
Bulk properties of nuclear matter in the relativistic Hartree approximation with cut-off regularization
Kazuharu Koide,Hiroaki Kouno,Akira Hasegawa,Masahiro Nakano
Physics , 1995,
Abstract: A method of cut-off regularization is proposed to evaluate vacuum corrections in nuclear matter in the framework of the Hartree approximation. Bulk properties of nuclear matter calculated by this method are a good agreement with results analyzed by empirical values. The vacuum effect is quantitatively evaluated through a cut-off parameter and its role for saturation property and compressional properties is clarified.
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