| Project/Area Number |
08640377
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
MUTA Taizo Hiroshima University, Department of Physics, Professor, 理学部, 教授 (80025353)
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| Co-Investigator(Kenkyū-buntansha) |
ONOGI Tetsuya Hiroshima University, Department of Physics, Research Associate, 理学部, 助手 (70211802)
MOROZUMI Takuya Hiroshima University, Department of Physics, Lecturer, 理学部, 講師 (20253049)
KADAIRA Jiro Hiroshima University, Department of Physics, Assistant Professor, 理学部, 助教授 (40127080)
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| Project Period (FY) |
1996 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1998: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1997: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
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| Keywords | Symmetry breaking / Chiral symmetry / Higgs model / Curved space-time / Gravitation / Nambu-Jona-Lasinio model / Supersymmetry / 動的対称性の破れ / 対称性 / 宇宙初期 / 複合物 / 複合場 / 重力場 / 場の量子論 / 相転位 / 対称性の自発的破れ |
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| Research Abstract |
At the early stage of the expanding universe, in particular at the period of grand unified theories when the inflation takes place, the universe is influenced by the strong classical gravity which keeps the space-time curved. The inflationary expansion is caused by the Higgs field. In the ordinary inflation scenario the Higgs field is preassumed to be 'elementary' and its vacuum expectation value is a free parameter. We considered the possibility that the Higgs field is a composite field composed of a pair of fermions and investigated the cosmological consequences of this assumption. Our results are summarized as follows;
(1)As a prototype model of the composite Higgs model we adopt the Nambu-Jona-Lasinio model and studied the phase structure of the model under the condition of the early universe with curved space-time and high temperature and density. We found the 2nd order phase transition.
(2)We studied the phase structure of Abelian gauge theories at finite temperature by using the Schwinger-Dyson equation in the real time formalism. We found the clear signal of the 2nd order phase transition.
(3)We examined the supersymmetric Nambu-Jona-Lasinio model with a soft supersymmetry breaking term in the 1/N expansion method at finite temperature and curvature. We find that the 1st and 2nd order phase transition may take place depending on the strength of the coupling constant and the soft breaking constant.
The above results were applied to the universe in the inflationary era and we find that the cosmic strings may be produced in this era.
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