Thermodynamics and equilibrium structure of Ne_38 cluster: Quantum Mechanics versus Classical

The equilibrium properties of classical LJ_38 versus quantum Ne_38 Lennard-Jones clusters are investigated. The quantum simulations use both the Path-Integral Monte-Carlo (PIMC) and the recently developed Variational-Gaussian-Wavepacket Monte-Carlo (VGW-MC) methods. The PIMC and the classical MC simulations are implemented in the parallel tempering framework. The VGW method is used to locate and characterize the low energy states of Ne_38, which are then further refined by PIMC calculations. Unlike the classical case, the ground state of Ne_38 is a liquid-like structure. Among the several liquid-like states with energies below the two symmetric states (O_h and C_5v), the lowest two exhibit strong delocalization over basins associated with at least two classical local minima. Because the symmetric structures do not play an essential role in the thermodynamics of Ne_38, the quantum heat capacity is a featureless curve indicative of the absence of any structural transformations. Good agreement between the two methods, VGW and PIMC, is obtained.Comment: 13 pages, 9 figure

Explanation of quantum dot blinking without long-lived trap hypothesis

A simple model explaining the experimental data on QDs luminescence blinking is suggested. The model does not assume the presence of the long-lived electron traps. The bleaching of the QD luminescence is a result of the Auger assisted radiationless relaxation of the excitation through the deep surface states. Possible ways of the experimental verification of the model are discussed

Nikolaj Serikoff. Arabic Medical Manuscripts of the Wellcome Library. A Descriptive Catalogue of the H˘addad Collection (WMS Arabic 401–487)

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Gaussian resolutions for equilibrium density matrices

A Gaussian resolution method for the computation of equilibrium density matrices rho(T) for a general multidimensional quantum problem is presented. The variational principle applied to the ``imaginary time'' Schroedinger equation provides the equations of motion for Gaussians in a resolution of rho(T) described by their width matrix, center and scale factor, all treated as dynamical variables. The method is computationally very inexpensive, has favorable scaling with the system size and is surprisingly accurate in a wide temperature range, even for cases involving quantum tunneling. Incorporation of symmetry constraints, such as reflection or particle statistics, is also discussed.Comment: 4 page

Оптимизация антенной решетки с косекансной диаграммой направленности

The method of partial directional diagrams (PDD) synthesized vertical omnidirectional in azimuth plane antenna arrays (AR) with cosequences PDD form in the vertical plane. The AR optimum height on the criterion of maximum gain is determinated. It is shown that the optimum height of AR de-pends significantly on the losses in the microwave cables and in the signal divider.Методом парциальных диаграмм направленности (ДН) синтезированы вертикальные всенаправленные в азимутальной плоскости антенные решетки (АР) с косекансной формой ДН в вертикальной плоскости. Определена оптимальная высота АР по критерию максимального коэффициента усиления. Показано, что оптимальная высота АР существенно зависит от потерь в СВЧ-кабеле и делителе сигнала

Синтез конструкции антенной решетки

The problem of linear antenna construction synthesize is first formulated and solved. Linear antenna consists of antenna array (AR) and power divider (PD). Linear omnidirectional AR with cosecant pattern is synthesized using partial-beam method. Beam-forming scheme for this antenna is based on two directional unequal splitters. The article proposes itera-tive method considering AR and beam-forming scheme mutual effect in terms of scattering matrix. Synthesis results demonstrate rapid convergence of the process and provide optimal pattern.Впервые поставлена и решена задача синтеза конструкции линейной антенны, состоящей из антенной решетки (АР) и делителя мощности (ДМ). Методом парциальных диаграмм направленности (ДН) синтезированы вертикальные всенаправленные в азимутальной плоскости АР с косекансной формой ДН в вертикальной плоскости. ДМ сигнала типа "дерево" сформирован на базе делителей на 2 направления. Предложен итерационный процесс формирования оптимального делителя с учетом взаимного влияния излучателей и ДМ на базе матриц рассеяния. Результаты синтеза показывают быструю сходимость процесса при оптимальных полученных параметрах системы АР–ДМ

Combined effect of coherent Z exchange and the hyperfine interaction in atomic PNC

The nuclear spin-dependent parity nonconserving (PNC) interaction arising from a combination of the hyperfine interaction and the coherent, spin-independent, PNC interaction from Z exchange is evaluated using many-body perturbation theory. For the 6s-7s transition in 133Cs, we obtain a result that is about 40% smaller than that found previously by Bouchiat and Piketty [Phys. Lett. B 269, 195 (1991)]. Applying this result to 133Cs, leads to an increase in the experimental value of nuclear anapole moment and exacerbates differences between constraints on PNC meson coupling constants obtained from the Cs anapole moment and those obtained from other nuclear parity violating experiments. Nuclear spin-dependent PNC dipole matrix elements, including contributions from the combined weak-hyperfine interaction, are also given for the 7s-8s transition in 211Fr and for transitions between ground-state hyperfine levels in K, Rb, Cs, Ba+, Au, Tl, Fr, and Ra+.Comment: Revtex4 preprint 19 pages 4 table