用超对称幺正变换解双光子过程的Jaynes-Cummings模型

本文发现了描写双光子过程的Jaynes-Cummings哈密顿量的超对称结构.根据超对称量子力学理论,引入了超对称幺正变换使其哈密顿量对角化.从而,得到了它的本征值、本征态,同时也计算了态的演化和跃迁几率.     

多光子集体辐射原子的J-C模型超对称求解

根据已有的双光子情形具有两个集体辐射原子的Jaynes-Cumm ings(J-C)模型,将之推广到多光子情形。找出了该模型的超对称生成元,然后用超对称变换的方法十分简洁地求解出了它的能量本征值和能量本征态。     

二维各向同性变频率谐振子的超对称性及其不变量的超对称量子力学精确解

采用超对称量子力学与不变量相结合的方法讨论了二维各向同性变频率谐振子,给出了二维各向同性变频率谐振子的不变量,采用超对称量子力学方法精确求解了不变量的本征值和本征函数,并且给出了当频率恒定时,二维常频率谐振子的本征值和本征函数的精确解.最后对不变量的超对称性进行了讨论.     

在FBF背景下带反射边界条件的超对称t-J模型的代数Bethe ansatz方法

在阶化量子反散射的框架中,得到FBF背景下,带反射边界条件的超对称t－J模型的本征值和本征矢,及相应的Betheansatz方程．     

在FBF背景下带反射边界条件的超对称t–J模型的代数Bethe ansatz方法

在阶化量子反散射的框架中,得到FBF背景下,带反射边界条件的超对称t–J模型的本征值和本征矢,及相应的Betheansatz方程.     

超对称准经典近似和本征值问题

运用超对称准经典近似方法给出三维谐振子、氢原子的能谱,进而将该方法用于含角坐标的二阶微分方程,得到角动量平方L2的本征值和非中心势的角向本征值.     

坐标算符本征矢的表示与不对称投影算符的积分

借助于粒子数算符的本征态和坐标算符函数的本征方程,把坐标算符的本征矢〈f(x)|表示为一个算符对坐标本征矢〈x|的作用.由此,把不对称的坐标投影算符转换为对称的坐标投影算符,再利用坐标本征矢的完备性,给出不对称坐标投影算符的积分. 关键词： 本征矢 算符的积分 本征方程 完备性     

Dirac类氢原子的超对称方法研究

应用超对称方法研究了Ｄｉｒａｃ类氢原子问题，不需繁琐的数学处理，得到和严格解法完全一致的能量本征值谱及相应的本征函数。     

在s=3/2情形下利用超对称量子力学方法解广义椭球函数

本文利用超对称量子力学的方法研究出广义椭球函数. 首先, 用超对称量子力学方法近似的算出前四阶超势W和相应本征值E, 然后递推出W_n的通式, 并利用数学归纳法来证明W_n通式的正确性, 从而得到了此时的广义椭球函数方程的基态波函数, 这对于它们的应用有很大的意义.     

具有广义Kratzer势的三维薛定谔方程的精确解

用超对称量子力学方法讨论了广义Kratzer势的形状不变性,并计算了它的能量本征值.传统的Kratzer势和改进的Kratzer势都是广义Kratzer势的特例.在此基础上,计算了双原子分子CO和NO在不同的径向量子数n_r和角量子数l时的能量本征值的具体数值.     

Exploring the operation of a tiny heat engine

We model a tiny heat engine as a Brownian particle that moves in a viscous medium in a sawtooth potential (with or without load) assisted by alternately placed hot and cold heat baths along its path. We find closed form expression for the steady-state current as a function of the model parameters. This enables us to deal with the energetics of the model and evaluate either its efficiency or its coefficient of performance depending upon whether the model functions either as a heat engine or as a refrigerator, respectively. We also study the way current changes with changes in parameters of interest. When we plot the phase diagrams showing the way the model operates, we not only find regions where it functions as a heat engine and as a refrigerator but we also identify a region where the model functions as neither of the two.     

Stochastic resonance in a monostable system driven by square-wave signal and dichotomous noise

<正>This paper investigates the stochastic resonance in a monostable system driven by square-wave signal,asymmetric dichotomous noise as well as by multiplicative and additive white noise.By the use of the properties of the dichotomous noise,it obtains the expressions of the signal-to-noise ratio under the adiabatic approximation condition.It finds that the signal-to-noise ratio is a non-monotonic function of the asymmetry of the dichotomous noise,and which varies non-monotonously with the intensity of the multiplicative and additive noise as well as the system parameters.Moreover, the signal-to-noise ratio depends on the correlation rate and intensity of the dichotomous noise.     

Stochastic resonance in a stochastic bistable system subject to additive white noise and dichotomous noise

The stochastic resonance (SR) in a stochastic stable system driven by a static force and a periodic square-wave signal as well as by additive white noise and dichotomous noise is considered from the point of view of the signal-to-noise ratio (SNR). It is found that the SNR exhibits SR behavior when it is plotted as a function of the noise strength of the white noise and dichotomous noise, as well as when plotted as a function of the static force. Moreover, the influence of the strength of the stochastic potential force and the correlation rate of the dichotomous noise is investigated.     

Electronic density of states in sequence dependent DNA molecules

We report in this work a numerical study of the electronic density of states (DOS) in π-stacked arrays of DNA single-strand segments made up from the nucleotides guanine G, adenine A, cytosine C and thymine T, forming a Rudin-Shapiro (RS) as well as a Fibonacci (FB) polyGC quasiperiodic sequences. Both structures are constructed starting from a G nucleotide as seed and following their respective inflation rules. Our theoretical method uses Dyson’s equation together with a transfer-matrix treatment, within an electronic tight-binding Hamiltonian model, suitable to describe the DNA segments modelled by the quasiperiodic chains. We compared the DOS spectra found for the quasiperiodic structure to those using a sequence of natural DNA, as part of the human chromosome Ch22, with a remarkable concordance, as far as the RS structure is concerned. The electronic spectrum shows several peaks, corresponding to localized states, as well as a striking self-similar aspect.     

Black Holes Are One-Dimensional

The holographic principle has revealed that phyical systems in 3-D space, black holes included, are basically two-dimensional as far as their information content is concerned. This conclusion is complemented by one sketched here: as far as entropy or information flow is concerned, a black hole behaves as a one-dimensional channel. We define a channel in flat spacetime in thermodynamic terms, and contrast it with common entropy emitting systems. A black hole is more like the former: its entropy output is related to the emitted power as it would be for a one-dimensional channel, and disposal of an information stream down a black hole is limited by the power invested in the same way as for a one-dimensional channel.     

Subnatural linewidth biphotons with controllable temporal length

This Letter describes the generation of biphotons with a temporal length that can be varied over the range of 50-900 ns, with an estimated subnatural linewidth as small as 0.75 MHz. We make use of electromagnetically induced transparency and slow light in a two-dimensional magneto-optical trap with an optical depth as high as 62. We report a sharp leading edge spike that is a Sommerfeld-Brillouin precursor, as observed at the biphoton level.     

Magnetic susceptibility in a layered superlattice

Paramagnetic and diamagnetic contributions to the magnetic susceptibility are calculated for a layered superlattice as a function of the temperature in both degenerate and nondegenerate regimes. The susceptibility shows distinctly different temperature dependences as the inter-layer bandwidth as well as the Fermi energy is varied from a two-dimensional to a three-dimensional regime, thus giving valuable information about the electron density and the inter-layer tunneling.     

A new 4π geometry optimized for focusing on an atom with a dipole-like radiation pattern

Focusing electromagnetic radiation efficiently onto an atom requires an open geometry, which is as close to the full solid angle as possible. Additionally, the radiant intensity should be as close as possible to a dipole radiation in order to have a similar field distribution as in the emission process. Here, we propose to make use of a novel combination of a parabolic mirror and a diffractive optical element.     

Decreasing electrical resistivity of silver along the melting boundary up to 5 GPa

The electrical resistivity of Ag was experimentally measured at high pressures up to 5?GPa and at temperatures up to ～300?K above melting. The resistivity decreased as a function of pressure and increased as a function of temperature as expected and is in very good agreement with 1 atm data. Observed melting temperatures at high pressures also agree well with previous experimental and theoretical studies. The main finding of this study is that resistivity of Ag decreases along the pressure- and temperature-dependent melting boundary, in conflict with prediction of resistivity invariance. This result is discussed in terms of the dominant contribution of the increasing energy separation between the Fermi level and 4d-band as a function of pressure. Calculated from the resistivity using the Wiedemann–Franz law, the electronic thermal conductivity increased as a function of pressure and decreased as a function of temperature as expected. The decrease in the high pressure thermal conductivity in the liquid phase as a function of temperature contrasts with the behavior of the 1 atm data.     

Reflection and transmission of ballistic electrons at a potential barrier

The reflection as well as transmission of ballistic electrons at a potential barrier is studied as a function of the angle of incidence. The samples are based on high mobility two dimensional electron gases in AlGaAs/GaAs -heterostructures using split gate point contacts for collimated emission as well as detection of ballistic electron beams. The variable electrostatic barrier is formed as a depletion space charge layer by biasing a 45° tilted gate strip. An external magnetic field is used to adjust the angle of incidence. The experimental results are compared to a model for the transmission and reflection coefficients at a potential boundary.