| Project/Area Number |
02640210
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
核・宇宙線・素粒子
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| Research Institution | Hirosaki University |
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Principal Investigator |
AKIBA Tomoya Hirosaki University, Faculty of Science, Professor, 理学部, 教授 (60004305)
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| Co-Investigator(Kenkyū-buntansha) |
YANAGIDA Tsutomu Tohoku University, Faculty of Science, Professor, 理学部, 教授 (10125677)
FUTAMASE Toshifumi Hirosaki University, Faculty of Science, Professor, 理学部, 教授 (20209141)
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| Project Period (FY) |
1990 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1992: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1991: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1990: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | Sphaleron / Relaxation of Baryon-Number / Baryonic Asymmetry of the Universe / Weinberg-Salam Model / ワインバ-グ・サラム模型 / バリオン数非保存 / ワイバ-グ・サラム模型 / 素粒子論 |
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| Research Abstract |
The Weinberg-Salam model for electro-weak interaction allows the process that violates the baryon- and lepton-nummber conservation laws. Although it is impossible to detect any effects of it by laboratory experiments, it presumably yielded the effect to convert baryons into leptons and vice versa during some period immediately after the weak-scale condensation in the cosmic evolution. This in turn has important clue to the origin of BAU (Baryonic Asymmetry of the Universe). It is believed that relaxation of the sum of the baryon and lepton numbers occurred by thermal transitions via a metastable state called sphaleron. The purpose of the present research is to advance our previous calculation on the sphaleron process which was published in two articles of Physical Review D. It also intended to elucidate the origin of BAU consistently with sphaleron process.
The main results obtained during 1990 - 1992 are:
(1) We derived a generalized Levinson theorem ^<4)>, which is used to identify all disrete-type spectra of eigen fluctuation modes at a sphaleron and facilitate calculation of the free energy of a sphaleron for various of the Higgs mass. The theorem is also expected to be useful to study bifurcation phenomena pertinent to the sphaleron equations.
(2) Some significant limits to the Majorana neutrino masses ^<2),5)> were obtained from the requirement that BAU should not be erased by cooperative action of sphaleron process and any lepton number-violating process. These limits provid some valuable hints to "beyond the standard model" ^<7)> as well as to possible scenarios of BAU.
The other results include a demonstration of the fermion-level crossing phenomenon in the sphaleron process ^<1)>, a description of the Boson star in terms of a sphaleron-like configuration ^<3)> and a BAU-scenario based on the supersymmetric SU(5) GUT ^<6)>.
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