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The purpose of this paper is to review the mechanisms and available theoretical methods for modeling the strength and failure of thin film/substrate systems 相似文献
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D. Gross 《Applied physics. B, Lasers and optics》2007,86(3):367-370
According to a classical result due to Hudson, the Wigner function of a pure, continuous-variable quantum state is non-negative
if and only if the state is Gaussian. We have proven an analogous statement for finite-dimensional quantum systems. In this
context, the role of Gaussian states is taken on by stabilizer states. The general results have been published in [1]. For
the case of systems of odd prime dimension, a different, greatly simplified method of proof can be employed which still exhibits
the main ideas. The present paper gives a self-contained account of these methods.
PACS 03.65.Fd; 03.65.Sq; 03.67.-a 相似文献
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Eugene P. Gross 《Journal of statistical physics》1989,54(1-2):405-427
A study is made of the ground-state energy of a spin-one-half particle in a fieldB and interacting with a phonon bath. The infrared-sensitive case of acoustic phonons with point coupling in three dimensions is characterized by two parameters, a coupling constant andB. Units are used where the high-momentum phonon cutoff is unity. There is a curve (B) separating a symmetry-breaking region with a long-range phonon field from a normal region. Two simple, well-known, approximations are compared. The source theory yields discontinuities in the first derivatives of the energy with respect toB and whenB>e
–1 and an infinite-order transition whenB<e
–1, but is trivial in the large- region. The classical theory yields discontinuities in the second derivatives but is trivial in the small- region. An improved variationally fixed ground-state wave function is analyzed. It gives a new (B) curve with an infinite-order transition with continuous energy derivatives whenB<e/(e
2–1/4) and with discontinuous derivatives whenB is larger than this value. It is nontrivial in the entire (B) plane. The crossover to classical behavior occurs near =1/2 forB1. But the wave function does not describe quantum fluctuations in the large- phase. A second way of combining source and classical effects is described. It yields a second-order transition (near =1/2 forB1) everywhere. These theories are special cases of a symmetry-breaking transformation together with a one-mode treatment of quantum fluctuations. The transition is viewed in terms of a single mode with a variable length, coupled dynamically to the spin. 相似文献