排序方式: 共有7条查询结果,搜索用时 15 毫秒
1
1.
Embedded random matrix ensembles are generic models for describing statistical properties of finite isolated interacting quantum many-particle systems. For the simplest spinless fermion (or boson) systems, with say m fermions (or bosons) in N single particle states and interacting via k-body interactions, we have EGUE(k) [embedded GUE of k-body interactions] with GUE embedding and the embedding algebra is U(N). A finite quantum system, induced by a transition operator, makes transitions from its states to the states of the same system or to those of another system. Examples are electromagnetic transitions (then the initial and final systems are same), nuclear beta and double beta decay (then the initial and final systems are different), particle addition to or removal from a given system and so on. Towards developing a complete statistical theory for transition strength densities (transition strengths multiplied by the density of states at the initial and final energies), we have derived formulas for the lower order bivariate moments of the strength densities generated by a variety of transition operators. Firstly, for a spinless fermion system, using EGUE(k) representation for a Hamiltonian that is k-body and an independent EGUE(t) representation for a transition operator that is t-body and employing the embedding U(N) algebra, finite-N formulas for moments up to order four are derived, for the first time, for the transition strength densities. Secondly, formulas for the moments up to order four are also derived for systems with two types of spinless fermions and a transition operator similar to beta decay and neutrinoless beta decay operators. In addition, moments formulas are also derived for a transition operator that removes k0 number of particles from a system of m spinless fermions. In the dilute limit, these formulas are shown to reduce to those for the EGOE version derived using the asymptotic limit theory of Mon and French (1975). Numerical results obtained using the exact formulas for two-body (k=2) Hamiltonians (in some examples for k=3 and 4) and the asymptotic formulas clearly establish that in general the smoothed (with respect to energy) form of the bivariate transition strength densities take bivariate Gaussian form for isolated finite quantum systems. Extensions of these results to bosonic systems and EGUE ensembles with further symmetries are discussed. 相似文献
2.
Recently pattern formation in layered structures, showing complicated superimposed patterns, has been modeled by coupling two Turing systems linearly, i.e., passively, such that the characteristic length scales of the independent systems are well separated. Here we propose a model of two non-linearly coupled Turing systems to study pattern formation in layered membrane-like structures, where the coupling plays an active role and changes the kinetics of the uncoupled systems. Extensive numerical simulations show that non-linear coupling generates a number of new regular patterns different from the ones observed earlier with linearly coupled systems. Some of them turn out to be superimposed patterns with different length scales, but many are not. Also, contrary to the linear coupling case, the strength of the non-linear coupling is found to play an important role in the formation and selection of patterns. 相似文献
3.
Zhu-Lian Tao Shang'an Yan Song-Lin Wu 《Journal of Mathematical Analysis and Applications》2007,331(1):152-158
We prove the existence of nontrivial critical points for a class of superquadratic nonautonomous second-order Hamiltonian systems by applying condition ∗(C) to critical point theory, and some new solvability conditions of nontrivial periodic solutions are obtained. 相似文献
4.
LD泵浦Nd:YAG/LBO蓝光激光器的低噪声运转 总被引:8,自引:4,他引:4
观察了LD泵浦Nd:YAG晶体,I类临界相位匹配LBO晶体腔内倍频的473nm蓝光激光器的噪声特性,指出蓝光噪声主要来自于不同纵模的相互耦合,并用双折射滤光片技术实现了全固态蓝光激光器的低噪声稳定运转在1.3W的泵浦功率下,获得了58mW的蓝光低噪声稳定输出. 相似文献
5.
6.
Fu-qiang Jia Qing-hua Xue Quan Zheng Yi-kun Bu Long-sheng Qian 《Optics & Laser Technology》2007,39(5):1081-1083
We report on a laser diode end-pumped Nd:YAG blue laser using a three-mirror-folded cavity. Three different crystals cut for type-I critical phase matching are used for the intra-cavity frequency doubling of the laser: 10-mm-long LiB3O5 (LBO), 15-mm-long LBO, and 10-mm-long BiB3O6 (BIBO). Up to 2.41 W of continuous wave output power in the blue spectral range at 473 nm is achieved with BIBO crystal (1.89 W with LBO) at the incident pump power of 16 W, the light-to-light conversion efficiency is about 15.1%. 相似文献
7.
Ping Lin Xintao Wu Ling Chen Wenxin Du Yifan Zheng 《Journal of chemical crystallography》1999,29(5):581-586
The complex (Ph4P)2[Mo2S2O2(S2)(S4)] reacts with CuBr to give the dodecanuclear heterobimetallic Mo—Cu—S cage cluster: (Ph4P)2[{Mo2Cu2O2S2(S2)2}3(473q752tr63/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">6-S)] (1), which crystallizes in the triclinic space group P1¯, a = 14.445(5), b = 15.396(5), c = 18.858(5) Å, 473q752tr63/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> = 103.12(3), 473q752tr63/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> = 101.93(2), 473q752tr63/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"> = 113.92(3)°, and V = 3517(2) Å3 for Z = 2. The anion 1 can be described as a cage with S2– at the center binding to six Cu atoms; the cage has two big windows each composed of a puckered Cu3S6 9-membered ring. 相似文献
1