Kerr介质中光场与Ⅴ型三能级原子依赖强度耦合相互作用系统的光场压缩

利用全量子理论,研究了Kerr介质中单模光场与v型三能级原子依赖强度耦合的相互作用系统中光场的压缩效应.采用数值计算的方法讨论了Kerr介质与辐射场的耦合系数x和初始场平均光子数对光场压缩的影响.结果表明:Kerr效应对光场的压缩起着不同程度的减弱作用,适当大小的初始场平均光子数有利于光场的压缩.     

Kerr介质中耦合V型三能级原子与相干态光场作用场的量子性质

研究了Kerr介质中相干态光场与耦合V型三能级原子相互作用过程中场的量子性质.利用量子光学中光场与原子相互作用的耦合Tavis-Cummings模型,对系统的动力学过程进行了求解.讨论了系统初始状态、失谐量、原子间偶极相互作用强度及Kerr系数对光场量子性质随时间演化的影响.数值计算结果表明:初态中场的平均光子数比较小时,光场能够展现出明显的量子效应|初始时刻原子激发态概率幅从小变大时,光场的反聚束效应变得越明显,而光场的压缩深度会先增大后减小|失谐量的变化对场的量子性质的影响不大,只是改变光场二阶相关函数和压缩参量振荡的周期|原子间耦合强度的增大使光场的反聚束效应减弱和光场的压缩深度变浅|Kerr系数的增大会增强光场的反聚束效应,而使光场的压缩深度变浅.     

Kerr介质中V型三能级原子与双模奇偶纠缠相干光场相互作用的纠缠特性

运用量子约化熵研究了Kerr介质中V型三能级原子与双模奇偶纠缠相干光场相互作用系统中场熵的演化特性.分析了Kerr介质、失谐量和光场的初始平均光子数对场熵的影响.结果表明:Kerr介质与光场的耦合系数对场熵的振荡特性有调制作用,增大失谐量,场熵的最大值减小,振荡频率增大,由初始时刻的零值增大到最大值所需的时间也增大;光场的平均光子数太大或太小都不利于原子与光场之间的纠缠.     

Kerr介质中与V型三能级原子依赖强度耦合系统光场的二阶相干性质

利用全量子理论,研究了存在Kerr介质时,单模光场与V型三能级原子依赖强度耦合系统的非共振相互作用系统中光场的二阶相干性质.讨论了Kerr介质与光场耦合常数、初始光场的平均光子数和失谐量对光场的二阶相干度的影响.     

非旋波近似下光场与V型三能级原子依赖强度耦合作用系统中的光场压缩

利用全量子理论,研究了非旋波近似下单模光场与V型三能级原子依赖强度耦合的相互作用系统中光场的压缩效应.结果表明:光场的压缩依赖于系统的本身性质,而虚光子过程使光场的压缩程度明显加强并产生量子噪声,其大小依赖于初始场平均光子数n和光场频率ω,且与原子光场耦合强度g有关.     

Kerr介质中双光子T-C模型光场的量子特性

研究了存在Kerr介质时，耦合双原子与单模压缩真空场双光子跃迁相互作用系统光场的量子特性，讨论了Kerr介质和原子间偶极-偶极相互作用对光场量子特性的影响. 结果表明：当Kerr效应和偶极-偶极相互作用可以忽略时，光场U2分量的涨落能被周期性地压缩，随着Kerr效应和偶极-偶极相互作用的增强，光场的压缩逐渐变浅，压缩次数减少；Kerr效应和偶极-偶极相互作用的影响使光场的二阶相干度时间演化曲线呈现周期性的崩塌-回复现象，但不论耦合强度如何，光子总是呈现聚束效应. 关键词： Kerr介质 压缩真空场 耦合双原子 光场的量子特性     

Kerr介质中双模纠缠相干光与Bell态原子相互作用系统的原子偶极压缩

运用全量子理论并结合数值计算方法，研究了Kerr介质腔中处于Bell态的两个全同二能级纠缠原子与双模纠缠相干光场相互作用系统的原子偶极压缩特性.讨论了双原子体系的初态、光场的平均光子数、双模纠缠相干光场的纠缠程度以及Kerr介质与双模光场的耦合强度对原子偶极压缩特性的影响.结果表明：双原子体系的初态为|β₁₁>时，不会出现偶极压缩效应；初态为|β₀₀>，|β₀₁>或|β₁₀>时在一定条件下可能出现原子压缩效应，且此时原子压缩的特性与Kerr介质与双模光场的耦合强度、初始光场的平均光子数、双模纠缠相干光场的纠缠程度有关. 关键词： 量子光学 Bell态 双模纠缠相干光场 Kerr介质     

Kerr介质腔中非关联双模热光场与V型三能级原子相互作用中的场关联特性

研究了Kerr介质腔中非关联双模热光场与V型三能级原子相互作用过程中的场关联特性.通过数值计算和图形分析,讨论了平均光子数、Kerr介质、失谐量以及耦合系数对场的关联特性的影响.结果发现:当V型三能级原子与两模光场发生相互作用时,非关联双模热光场将发生关联,且关联强度与耦合强度、失谐量和Kerr系数有关.当两模热光场和裸原子发生对称相互作用时,两模光场始终处于正关联;增加一模光场的平均光子数,两模光场的关联减弱;Kerr介质和失谐量的增加将削弱两模场的关联;当两模光场与原子发生不对称相互作用时,假设g1>g2,两模光场的关联特性在正关联和反关联之间交替出现.保持场一模的平均光子数不变,增加场另一模的平均光子数,反关联特性消失.     

Kerr介质对双模压缩真空场与四能级原子相互作用系统中光场量子特性的影响

研究了旋波近似下Kerr介质中双模压缩真空场与N型四能级原子双光子跃迁相互作用系统中光场的压缩效应及光子的统计性质.数值计算结果表明,在无Kerr介质的情况下,光场的两个正交分量的均方涨落均呈现周期性的压缩,光子周期性地交替呈现聚束和反聚束效应,光场两模之间总是呈现正相关,而且这种相关是非经典相关;Kerr介质的存在不利于光场均方涨落的压缩,但对光子统计性质没有明显的影响 关键词： Kerr介质 四能级原子 双模压缩真空场 光场的量子特性     

双模纠缠相干光场与Bell态原子相互作用系统的光场压缩效应

运用求解Schrdinger方程和数值计算方法,研究了处于Bell态的两个全同二能级纠缠原子与双模纠缠相干光场相互作用系统的光场压缩特性,分析了双模纠缠相干光场的纠缠程度、双模纠缠相干光场的初始平均光子数对光场压缩性质的影响,以及两纠缠原子的相互作用强度对光场压缩性质的影响.结果表明:若初始时刻原子处在Bell态|β11〉,则不出现光场的压缩效应,而处在另外三种Bell态时,在一定的条件下均可呈现光场的压缩效应.光场压缩效应不仅与初始光场的平均光子数以及原子的初态有关而且与双模纠缠相干光场的纠缠程度有关,但与两纠缠原子的相互作用强度的大小没有明显的关系.     

Absorption in the final state in reactions and decays in the medium

The role of strong absorption of particles in intermediate and final states has been considered. The range of applicability of phenomenological models of absorption has been studied. This model is nonuniversal. Its applicability depends on the type of interaction Hamiltonian and matrix element used. We also demonstrate that the violation of the unitarity condition can produce a qualitative error in the results. The absorption (decay) in the final state does not tend to suppress the total process probability as well as the probability of the channel corresponding to absorption. This is true for the reactions, decays and nˉ conversion in the medium.     

Solutions of the BBGKI equations in the fourth approximation in the temperature

Solutions of the Bogolyubov-Born-Green-Kirkwood-Ivon equations in the fourth approximation in the temperature are given in a class of generalized functions both for van der Waals and ionic crystals in the case of the so-called taking into account of smoothed correlations. A statistical thermodynamics of strongly anharmonic van der Waals and ionic crystals is constructed. Temperature expansions of the correlative distribution functions and thermodynamic quantities are investigated within the framework of the indicated method. The temperature dependence of cubic order is taken into account in the expression of the isochoric specific heat and the Grüneisen parameter of the listed crystals. It is shown that the temperature expansion for the isochoric specific heat of anharmonic crystals converges well for a value of the reduced temperature 0.33 T_m (T_m is the melting temperature).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 55–59, July, 1981.     

Metastates in the Hopfield Model in the Replica Symmetric Regime

We study the finite dimensional marginals of the Gibbs measure in the Hopfield model at low temperature when the number of patterns, M, is proportional to the volume with a sufficiently small proportionality constant > 0. It is shown that even when a single pattern is selected (by a magnetic field or by conditioning), the marginals do not converge almost surely, but only in law. The corresponding limiting law is constructed explicitly. We fit our result in the recently proposed language of metastates which we discuss some length. As a byproduct, in a certain regime of the parameters and (the inverse temperature), we also give a simple proof of Talagrands recent result that the replica symmetric solution found by Amit, Gutfreund, and Sompolinsky can be rigorously justified.     

在稳定中求变在变化中求新——2010年高考浙江省理综(物理)试题评析

1 总体特征 通读2010年高考浙江省理综卷物理试题,给人以耳目一新的感觉.命题者在2010年的命题设计中,做到了三个贴近,即贴近时代、贴近生活、贴近学生.实现了三个有利的原则,即"有利于高等学校选拔新生,有利于中学推行素质教育,有利于激发考生学习科学的兴趣".     

Role of the near-electrode regions in the formation of the volume discharge heterogeneity in nitrogen in the pin-to-plane configuration

The development of streamers and sparks in nitrogen at atmospheric pressure in the pin-to-plane electrode configuration is studied in experiments and theoretical calculations. It is demonstrated that the near-electrode regions play the decisive role in streamer initiation. At a negative pin voltage, a spark is formed in the absence of fast primary streamers. At a positive pin voltage, streamer build-up is initiated by the current spots on the anode that result from the development of the ionization instabilities in the anode region. The calculations show that the formation of the current spot on the anode leads to a redistribution of the electric field in the vicinity of the anode, so that a single avalanche is transformed into a streamer under the conditions when the known criterion for streamer breakdown (the Meek-Raether criterion) is not satisfied. Original Text ? Astro, Ltd., 2006.     

Superconductivity in the t-J model in the large-N limit

Using a 1/N expansion for X-operators the leading contributions to the linearized equation for the superconducting gap of the t-J model are derived and the gap equation solved numerically on a square lattice. We find a strong instability towards superconductivity only in the d-wave (T ₃) channel with T _c/│t│ ～ 0:01 where T _c is the transition temperature and t the nearest-neighbor hopping integral. The underlying effective interaction consists of an attractive, instantaneous term with the band width, and a retarded term due to charge and spin fluctuations with ～ J, as energy scale.     

Change in the sign of the magnetoresistance effect in bilayer superconductor/ferromagnet structures under change in the type of the domain structure in the ferromagnet

The magnetoresistance effects in the bi- and trilayer hybrid planar superconductor/ferromagnet (S/F) structures based on Py (permalloy) and Nb near the superconducting transition temperature T _C are considered. It has been experimentally shown that the sign of the observed magnetoresistance peaks in the bilayer S/F systems changes from negative to positive at the permalloy layer thickness corresponding to the change in the type of domain walls from Néel to Bloch. For the Néel walls at the ferromagnet coercive fields, the negative magnetoresistance effect, which is due to a decrease in the depairing action of the exchange field E _ex, is observed in the S/F bilayers. For the Bloch domain walls, the magnetoresistance of the bilayer S/F structures is determined by the dissipative motion of Abrikosov vortices in the superconducting layer. In the trilayer F/S/F structures, the magnetoresistance is mainly due to the suppression of the superconducting order parameter in the superconducting layer under the action of the accumulation of the spin-polarized carriers near the S/F interfaces.     

ZnO可见区发光机理研究进展

近年来,科研工作者对ZnO纳米材料研究产生了浓厚的兴趣。ZnO是一种具有宽带隙(3.37 eV)和较大的激子束缚能(60 meV)的六方纤锌矿结构半导体材料。它具有优异的光电、压电、压敏及发光等特性,在发光(激光)二极管、传感器、发光器件、紫外探测器等领域都有非常好的应用前景。至今,有很多非常成熟的实验方法(包括静电纺丝、水热法、溶胶-水热法、化学气相沉积法、旋涂法及电化学沉积法等)用来合成ZnO纳米材料,如纳米线、纳米棒、纳米盘及量子点等。氧化锌纳米结构的制备和性质已得到了广泛的研究,ZnO的可见发光机理一直是研究的热点,但很少有人对可见光范围内的光致发光进行总结。光致发光光谱能反映一些重要信息,如表面缺陷和氧空位、半导体材料的表面状态、光诱导电荷转移过程等。有学者认为ZnO的发光机理与其晶体缺陷有关,还有研究者认为其发光机理与氧空位有关等。通过量子限域效应、带边调制、表面修饰方法、缺陷调控方法等方面综述了ZnO可见区发光机理。     

On the origin of the intermediate component in the positron lifetime spectra in polymers

We have carried out an investigation of the nature of the 1 ns intermediate component in the positron time annihilation spectra of five polymers (atactic and isotactic polypropylene, polymethylmethacrylate, teflon, and polyethylene), using the magnetic quenching technique at high fields (1.5–3 T), coupled to lifetime spectroscopy. The results indicate that this component comes from the decay of a positron-electron bound system, different from that associated with the longest lifetime component. Therefore, two different Ps-like systems must be considered in the investigated polymers.     

Computational modelling for the clustering degree in the saturated steam and the water-containing complexes in the atmosphere

Recent computational findings of temperature increase of clustering degree in several quite different saturated vapors are analyzed further. A thermodynamic proof is presented, showing that this event should be rather common, if not general. Illustrations are based on the saturated steam and consequences for the atmosphere are discussed with both homo- and hetero-clustering. MP2=FC/6-311G^** results for the H₂O·N₂ (the best stabilization energy , which corresponds to with the G3 theory) and H₂O·O₂ (the best stabilization energy ) hetero-dimers, and the G1-theory (O₂)₂ data (the best stabilization energy ) are reported. The water-dimer thermodynamics is recomputed in an anharmonic regime and a remarkable agreement with experiment is found. The results have some significance for the atmospheric greenhouse effect.