Theory of Macroscopic Quantum Phenomena
| Project/Area Number |
08640471
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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 |
物性一般(含基礎論)
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| Research Institution | Tohoku University |
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Principal Investigator |
TAKAGI Shin Tohoku Univ.Dep.Phys.Assoc.Prof., 大学院・理学研究科, 助教授 (90124594)
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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 |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1998: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1997: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
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| Keywords | MQP / MQT / MQC / Macroscopic Quantum Tunnelling / Macroscopic Quantum Coherence / Macroscopic Quantum Nucleation / Bounce / Spin-Coherent-State Path Integral / 巨視的量子現象 / 巨視的量子崩壊 / コヒーレント状態経路積分 / スピン・コヒーレント状態経路積分 / 磁壁の量子力学 / 量子崩壊 / 巨視的量子コヒーレンス / トンネル効果 / コヒーレンス / 量子的不満効果 / シュレ-ディンガーの方角 / 量子トンネル現象 / 量子コヒーレンス / ディコヒーレンス / 量子核形成 / シュレ-ディンガーの猫 |
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| Research Abstract |
* Macroscopic Quantum Pheniomena (of the second kind), to be abbreviated as MQP, are those phenomena which involve macroscopic number of degrees of freedom in a linear superposition of macroscopically distinct states and yet are characterised by an action of the order of Planck's constant. Fundamental ideas (basic concepts, classifications, phenomenological theories, detection methods and associated quantum measurement problem, and so on) were delineated in a form easily accessible for current and future workers.
* Of crucial importance in describing MQP is the choice if collective degrees of freedom. Two systems were discussed in detail as typical examples :
(a) Quantum nucleation in quantum fluids : Radius of the emerging nucleus as the collective degrees of freedom.・ Tentative estimate of the nucleation rate.・Limitation in the so-far standard phenomenology pointed out and remedied.
(b) Quantum resonant oscillation between two chirality states of a ferromagnetic domain wall : Chirality as the collective degree of freedom. ・ Possibility of a magnetic version of the Cat ・ Semi-quantitative estimate of the resonance frequency.
* Those quantum decay phenomena such as macroscopic quantum nucleation from an important class of MQP.Theoretical foundation of the bounce method, which is a method of evaluating the nucleation rate, had ben left obscure in spite of its popularity. The basic conditions needed to justify the method were clarified ; whether these conditions are actually met or not is a problem yet to be settled.
* Some fundamental difficulties in the continuous-time formation of spin-coherent-state path integral, which had been (and still are) overwhelmingly used in dealing with quantum-mechanical behavior of a magnetic domain wall, were pointed out and a way out was suggested. Applications to concrete examples are left to future investigations.
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Report
(4 results)
Research Products
(24 results)
