四颗南天脉冲星在1560 MHz上的偏振观测

本文给出88年6月和7月期间在澳大利亚Parkes进行的一次南天脉冲星偏振观测的部分有意义的结果。频率为1560MHz。采用了Jodrell Bank天文台新研制成的2×16×5MHz滤波系统,使这次观测具有很强的消色散能力和较高的灵敏度。这4颗南天脉冲星具有较强的线偏振,为首次获得的高频偏振资料。

3C273宽线云中HI区域温度、Lyα线强度与谱指数的相关性

本文用IUE天文台的类星体3C 273的紫外监测资料,测量了该源不同时间紫外光谱中Lyα线的强度f(Lyα),并且估测了"切仑柯夫红移",定出了能级2的粒子数布居R_2;综合观测到的线强比I(H_α)/I(H_β)和I(Lyα)/I(H_β),定出了3C 273在三个不同时间的宽线云HI区温度T分别为12000K,9100K和8600K,这些T值与紫外谱指数α_(uv)明显相关,且α_(uv)与f(Lyα)有单调递增关系,表明了用切仑柯夫线辐射理论解释类星体宽线区模型能与观测相符.反过来,这种与观测相符的解释也是对切仑柯夫线辐射理论的有力支持.

Probabilistic Teleportation of an Unknown Two-Particle State with a Four-Particle Pure Entangled State and Positive Operator Valued Measure

We propose a scheme for probabilistic teleportation of an unknown two-particle state with a four-particle pure entangled state and positive operator valued measure （POVM）. In this scheme the teleportation of an unknown two-particle state can be realized with certain probability by performing two Bell state measurements, a proper POVM and a unitary transformation.

A Simultaneous Quantum Secure Direct Communication Scheme between the Central Party and Other M Parties

We propose a simultaneous quantum secure direct communication scheme between one party and other three parties via four-particle GHZ states and swapping quantum entanglement. In the scheme, three spatially separated senders, Alice, Bob and Charlie, transmit their secret messages to a remote receiver Diana by performing a series of local operations on their respective particles according to the quadripartite stipulation. From Alice, Bob, Charlie and Diana＇s Bell measurement results, Diana can infer the secret messages. Ira perfect quantum channel is used, the secret messages are faithfully transmitted from Alice, Bob and Charlie to Diana via initially shared pairs of four-particle GHZ states without revealing any information to a potential eavesdropper. As there is no transmission of the qubits carrying the secret message in the public channel, it is completely secure for the direct secret communication. This scheme can be considered as a network of communication parties where each party wants to communicate secretly with a central party or server.

General Laser Intensity Langevin Equation in a Single-Mode Laser Model

A two-dimensional single-mode laser model with cross-correlations between the real and imaginary parts of the quantum noise as well as the pump noise is investigated.The general closed form of the laser intensity Langevin equation(GILE)is obtained under a stable locked phase resulting from the cross-correlationλ_(q) between the real and imaginary parts of the quantum noise.Because of the presence of a new term containingλ_(q),we can unify the two opposite intensity Langevin equations which correspond to the two special cases for|λ_(q)|→0 and|λ_(q)|→1 in the GILE.It is expected that the transient and stationary properties of the laser model can be changed qualitatively whenλ_(q) varies.

Polaron Energy and Effective Mass in Parabolic Quantum Wells

The energy and effective mass of a polaron in a parabolic quantum well are studied theoretically by using LLP-like transformations and a variational approach. Numerical results are presented for the polaron energy and effective mass in the GaAs/Al0.3Ga0.7As parabolic quantum well. The results show that the energy and the effective mass of the polaron both have their maxima in the finite parabolic quantum well but decrease monotonously in the infinite parabolic quantum well with the increasing well width. It is verified that the bulk longitudinal optical phonon mode approximation is an adequate formulation for the electron-phonon coupling in parabolic quantum well structures.

Statistical Properties of the Output Light Intensity in a Single-Mode Laser Driven by Correlated Noises

By using linear approximation we derive expressions for the correlation function,power spectrum and correlation time of the output light intensity in a single-mode laser driven by additive white noise and multiplicative colored noise with an exponential correlation form.The effects of correlation strength and correlation time of the noises on the above quantities are discussed and compared with the case of a delta function correlation form for the noises.

Polaronic Band Structure of Holstein Model

A new concise approach is presented for analytic study of the properties of the Holstein model. New analytic results for the polaronic band structure and phonon distribution, of the Holstein molecular crystal model, are given in one dimension. And all analytic results given are in accordance with the known numerical research results.

Ⅰ型Seyfert星系的3000包与其在双色图上的表现

本文从Ⅰ型Seyfert星系在双色图上的行为出发,假定可见光与紫外波段连续谱的主要成分包括幂律非热致辐射、黑体辐射、宽线区Balmer连续谱的复合辐射和高阶Balmer线辐射,计算了这些发射机制的参数,发现结果与从分光光度测量决定的参数符合很好。因此,本文结果对已测定色指数的Ⅰ型Seyfert星系可决定出其热致成分(黑体谱和Balmer连续谱)在全部辐射中占的比重;给出了研究类星体的可见光与紫外波段辐射机制的新方法。

Solution of Wheeler-De Witt Equation, Potential Well and Tunnel Effect

This paper uses the relation of the cosmic scale factor and scalar field to solve Wheeler-De Witt equation,gives the tunnel effect of the cosmic scale factor a and quantum potential well of scalar field, and makes it fit with the physics of cosmic quantum birth. By solving Wheeler-De Witt equation we achieve a general probability distribution of the cosmic birth, and give the analysis of cosmic quantum birth.

Reentrant Transitions Induced by Correlation Between Colored Noises

In the study,a bistable system is driven by additive colored noise and multiplicative colored noise,whose correlation is of an exponential farm.When the noises are correlated,it is found that the system undergoes a reentrant transition as the correlation strength between noises or multiplicative noise intensity changes,while there is no such phenomenon as the additive noise intensity or the time of correlation changes.No reentrant transition exists when the noises are uncorrelated.

Quantum-Mechanical Method for the Soliton Transported Bio-energy in Protein

The equations of motion of the soliton transported bio-energy in the protein,were heretofore already obtained by a combination of quantum-mechanical and classical methods,but here have been derived based completely on quantum mechanics.And we point out the shortcoming of no self-consistency of the Davydov theory.Some interesting results have also been got.

Escape Rate in the Bistable Sawtooth System Driven by Correlated Multiplicative and Additive White Noises

We study the escape problem of a bistable sawtooth system driven by correlated multiplicative and additive white noises.Exact analytic representation of the relative escape rate is obtained.Some novel phenomena are found from the calculation result;“suppression platform”appears in the relative escape rate when the noise correlation coefficientλis positive.Moreover,for small positive values ofλ,the relative escape rate exhibits“suppression platform”and then“resonant activation”with the increasing noise strength ratio R.

Influence of Noise on Time Evolution of Intensity Correlation Function

Using the linear approximation method, we have studied how the correlation function C（t） of the laser intensity changes with time in the loss-noise model of the single-mode laser driven by the colored pump noise with signal modulation and the quantum noise with cross-correlation between the real and imaginary parts. We have found that when the pump noise self-correlation time T changes, （i） in the case of r 〈〈 1, the C（t） vs. t curve experiences a changing process from the monotonous descending to monotonous rise, and finally to the appearance of a maximum; （ii） in the case of r 〉〉 1, the curve only exhibits periodically surging with descending envelope. When r 〈〈 i and T does not change, with the increase of the pump noise intensity P, the curve experiences a repeated changing process, that is, from the monotonous descending to the appearance of a maximum, then to monotonous rise, and finally to the appearance of a maximum again. With the increase of the quantum noise intensity O,, the curve experiences a changing process from the monotonous rise to the appearance of a maximum, and finally to the monotonous descending. The increase of the quantum noise with cross-correlation between the real and imaginary parts will lead to the fall of the whole curve, but not affect the form of the time evolution of C（t）.

Phenomenon of Resonance in a Two-Mode Laser with an Input Additive Signal

Exact formulas for the power spectrum and signal-to-noise ratio (SNR) with periodic additive signal arecalculated in the linear system.Then the phenomenon of resonance is studied in detail.We show that resonancepeak and suppressed valley exist in the curves of the SNR versus the coefficient of self-saturation, the net gain and thecross-coupling coefficient of the laser system.

Does There Exist Only One Solution of the Dyson-Schwinger Equation for the Quark Propagator in the Case of Non-Zero Current Quark Mass

It is shown on general ground that there exist two qualitatively distinct solutions of the Dyson-Schwinger equation for the quark propagator in the case of non-zero current quark mass. One solution corresponds to the “Nambu- Goldstone” phase and the other one corresponds to the “Wigner” phase in the chiral limit.

Propagation of a Rectangular Pulse in an Anomalous Dispersive Medium

The pulse with a rectangular envelop propagating through the caesium vapour with two gain lines used inthe Wang, Kuzmich, and Dogariu [Nature (London) 406 (2000) 277] experiment is studied. It is shown that there existsan obvious distortion for the pulse.

Correlation Function and Time-Dependent Moments of the Intensity for Gain-Noise Model of a Single-Mode Laser with Exponential Function Correlation Noise

The gain-noise model of a single-mode laser driven by correlated additive and multiplicative white noises is investigated theoretically.The analytical expressions of the time-dependent moments and correlation function of the laser intensity are derived by means of linear approximation method.Some novel phenomena are found.In certain cases,instead of monotonic evolution,the evolution curves of the intensity correlation function versus time exhibit the negative minimum value,whereas a peak for the evolution of the normalized variance of the laser intensity with time emerges.

A Test of Color-Octet Heavy Quarkonium Production Mechanism

Using the scale evolution of nuclear parton distributions,the contribution of color-octet heavy quarkonium production mechanism to the P + Fe → J/ψ + γ + X process in calculated and discussed.Comparing our theoretical results with the future experimental data,the color-octet heavy quarkonium production mechanism can be examined.

Capacity of a Simultaneous Quantum Secure Direct Communication Scheme between the Central Party and Other M Parties

We analyse the capacity of a simultaneous quantum secure direct communication scheme between the central party and other M parties via M＋1-particle GHZ states and swapping quantum entanglement. It is shown that the encoding scheme should be secret if other M parties wants to transmit M ＋ 1 bit classical messages to the centre party secretly. However, when the encoding scheme is announced publicly, we prove that the capacity of the scheme in transmitting the secret messages is 2 bits, no matter how large M is.