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Theory of Macroscopic Quantum Phenomena

宏观量子现象理论

基本信息

批准号：
08640471
负责人：
TAKAGI Shin
金额：
$ 1.34万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

* 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.

* 宏观量子现象（Macroscopic Quantum Pheniomena）（第二类），简称MQP，是指在宏观不同状态的线性叠加中涉及宏观自由度的现象，但其特征在于普朗克常数量级的作用。基本思想（基本概念、分类、现象学理论、探测方法和相关的量子测量问题等）以一种易于当前和未来工作者理解的形式被描述出来。在描述MQP时至关重要的是集体自由度的选择。作为典型例子，详细讨论了两个系统：（a）量子流体中的量子成核：新兴核的半径作为集体自由度。·成核率的初步估计。·指出并弥补了迄今为止标准现象学的局限性。(b)铁磁畴壁两个手征态之间的量子共振：手征作为集体自由度。·Cat的磁性版本的可能性·共振频率的半定量估计。*量子衰变现象如宏观量子成核是MQP的一个重要分支，而计算成核率的方法--反弹法的理论基础虽然得到了广泛的应用，但却一直不为人所知。证明这种方法的合理性所需的基本条件已经得到澄清;这些条件是否实际上得到满足是一个尚待解决的问题。指出了在研究磁畴壁量子力学行为时，自旋相干态路径积分在连续时间构造中存在的一些基本困难，并提出了解决方法.具体实例的应用留待将来研究。