双自由度诊断高能电子透镜成像技术

电磁场及流体演化过程信息的获取在高能量密度物理、可控核聚变及实验天体物理的研究中起着重要的作用,然而在实验过程中,电磁场信息及流体信息的同步获取是非常困难的。基于高能电子透镜成像技术,利用面密度差分的方法,提出了一种可以实现面密度和场积分强度同时获取的双自由度诊断设计方案。结合了蒙特卡罗模拟和束流光学分析,该方案在相对较强的电磁场情况下的适用性得到了验证。此外,我们可以通过改变Fourier面处光阑的形状将其适用区间扩展到低电磁场强度相空间。结合高能电子束相对论速度及超短脉冲的特点,该技术非常适用于磁流体超快演化过程的诊断。     

New integrable classical system with two degrees of freedom

It is shown that a classical system with hamiltonian $\text{H = (p}{}^2{}_1\text{+ p}{}^2{}_2\text{)/2 + λ(q}{}_1\text{q}{}_2\text{)}{}^{\mathrm{<mtext>-</mtext><mtext>2</mtext><mtext>3</mtext>}}$ possesses a constant of the motion $\text{K = p}{}_1\text{p}{}_2\text{(p}{}_1\text{q}{}_2\text{? p}{}_2\text{q}{}_1\text{) + 2λ(p}{}_2\text{q}{}_2\text{? p}{}_1\text{q}{}_1\text{)(q}{}_1\text{q}{}_2\text{)}{}^{\mathrm{<mtext>-</mtext><mtext>2</mtext><mtext>3</mtext>}}$; the quantum system with the same hamiltonian has no constants of the motion which are polynomials in the momenta of order not higher than three, except H.     

Heat transfer between two degrees of freedom

A particularly simple chaotic nonequilibrium open system with two Cartesian degrees of freedom, characterized by two distinct temperatures T(x) and T(y), is introduced. The two temperatures are maintained by Nose-Hoover canonical-ensemble thermostats. Both the equilibrium (no net heat transfer) and nonequilibrium (dissipative) Lyapunov spectra are characterized for this simple system.     

Horseshoes in perturbations of Hamiltonian systems with two degrees of freedom

This paper concerns Hamiltonian and non-Hamiltonian perturbations of integrable two degree of freedom Hamiltonian systems which contain homoclinic and periodic orbits. Our main example concerns perturbations of the uncoupled system consisting of the simple pendulum and the harmonic oscillator. We show that small coupling perturbations with, possibly, the addition of positive and negative damping breaks the integrability by introducing horseshoes into the dynamics.Research partially supported by ARO Contract DAAG-29-79-C-0086 and by NSF Grants ENG 78-02891 and MCS-78-06718     

A disordered ising model with internal degrees of freedom

A solvable Ising-system withnn-interactions as a basic system is considered. This system is assumed to undergo a phase transition so that the thermal quantityq=Σ _i> ₀ ² /N, which is not necessarily the order parameter of the basic system, is different from zero (q≠0) forT _c. The whole system consists of the basis {S _i} and an equal number of additional spins η _i which are coupled linearly with the basic spinsS _i through an exchange constantJ _i which is distributed at random. The pairs of spinsS _i ?η _i can be interpreted as clusters with an internal degree of freedom. The specific heat Δc and the susceptibility Δ_χ of the internal degree of freedom can be separated exactly and show typical spin glass properties: the specific heat Δc is an analytic function over the whole temperature range and the susceptibility Δ_χ shows a cusp at the transition temperatureT _c of the basic system.     

A disordered ising model with internal degrees of freedom

A solvable Ising-system withnn-interactions as a basic system is considered. This system is assumed to undergo a phase transition so that the thermal quantityq= _i> ₀ ² /N, which is not necessarily the order parameter of the basic system, is different from zero (q0) forT _c. The whole system consists of the basis {S _i} and an equal number of additional spins _i which are coupled linearly with the basic spinsS _i through an exchange constantJ _i which is distributed at random. The pairs of spinsS _i – _i can be interpreted as clusters with an internal degree of freedom. The specific heat c and the susceptibility of the internal degree of freedom can be separated exactly and show typical spin glass properties: the specific heat c is an analytic function over the whole temperature range and the susceptibility shows a cusp at the transition temperatureT _c of the basic system.     

Electromagnetism in terms of its two degrees of freedom

Electromagnetism is described in terms of two scalar gauge-invariant variables. The role of gauge freedom in the quantization process when A^μ(x) is written in momentum space appears as the indetermination of a two-dimensional space-like plane orthogonal to the (null) momentum k^μ plus a c-number arbitrary function. Duality rotations can naturally be described as the freedom to choose two orthonormal vectors in the two-dimensional space-like plane. The action written in terms of the two dynamical degrees of freedom is explicitly invariant under finite duality rotations and the associated Noether current is gauge invariant. Finally, we establish the equivalence for the Poisson bracket relations (PBR's) (based on equal time and equal null-time PBR for the two degrees of freedom) between A^μ(x) and A^ν(x′) for any gauge.     

Remote preparation for single-photon state in two degrees of freedom with hyper-entangled states

Remote state preparation (RSP) provides a useful way of transferring quantum information between two distant nodes based on the previously shared entanglement. In this paper, we study RSP of an arbitrary single-photon state in two degrees of freedom (DoFs). Using hyper-entanglement as a shared resource, our first goal is to remotely prepare the single-photon state in polarization and frequency DoFs and the second one is to reconstruct the single-photon state in polarization and time-bin DoFs. In the RSP process, the sender will rotate the quantum state in each DoF of the photon according to the knowledge of the state to be communicated. By performing a projective measurement on the polarization of the sender’s photon, the original single-photon state in two DoFs can be remotely reconstructed at the receiver’s quantum systems. This work demonstrates a novel capability for longdistance quantum communication.     

Superstrings with tensor degrees of freedom

We add antisymmetric tensor degrees of freedom to the usual superstring coordinates. We show that super and kappa symmetries are only achieved for the spacetime dimensionD=4. We also address problems related to the quantization of the model and discuss the influences of this extended spacetime in the usual quantum field theory.     

Collective states of odd nuclei in a model with quadrupole-octupole degrees of freedom

We apply the collective axial quadrupole—octupole Hamiltonian to describe the rotation—vibration motion of odd nuclei with Coriolis coupling between the even-even core and the unpaired nucleon.We consider that the core oscillates coherently with respect to the quadrupole and octupole axialdeformation variables. The coupling between the core and the unpaired nucleon provides a split paritydoublet structure of the spectrum. The formalism successfully reproduces the parity-doublet splitting in a wide range of odd-A nuclei. It provides model estimations for the third angular-momentum projection K on the intrinsic symmetry axis and the related intrinsic nuclear structure. The text was submitted by the authors in English.     

Coherent frequency conversion in a superconducting artificial atom with two internal degrees of freedom

By adding a large inductance in a dc-SQUID phase qubit loop, one decouples the junctions' dynamics and creates a superconducting artificial atom with two internal degrees of freedom. In addition to the usual symmetric plasma mode (s mode) which gives rise to the phase qubit, an antisymmetric mode (a mode) appears. These two modes can be described by two anharmonic oscillators with eigenstates |ns> and |na> for the s and a mode, respectively. We show that a strong nonlinear coupling between the modes leads to a large energy splitting between states |0s,1a> and |2s,0a>. Finally, coherent frequency conversion is observed via free oscillations between the states |0s,1a> and |2s,0a>.     

On chaotic dynamics in "pseudobilliard" Hamiltonian systems with two degrees of freedom

A new class of Hamiltonian dynamical systems with two degrees of freedom is studied, for which the Hamiltonian function is a linear form with respect to moduli of both momenta. For different potentials such systems can be either completely integrable or behave just as normal nonintegrable Hamiltonian systems with two degrees of freedom: one observes many of the phenomena characteristic of the latter ones, such as a breakdown of invariant tori as soon as the integrability is violated; a formation of stochastic layers around destroyed separatrices; bifurcations of periodic orbits, etc. At the same time, the equations of motion are simply integrated on subsequent adjacent time intervals, as in billiard systems; i.e., all the trajectories can be calculated explicitly: Given an initial data, the state of the system is uniquely determined for any moment. This feature of systems in interest makes them very attractive models for a study of nonlinear phenomena in finite-dimensional Hamiltonian systems. A simple representative model of this class (a model with quadratic potential), whose dynamics is typical, is studied in detail. (c) 1997 American Institute of Physics.     

Instability of traveling waves in an optical waveguide

Instability of traveling IR waves within a waveguide structure is discussed. A practical model of a traveling wave amplifier of a solid state is proposed, utilizing an optical waveguide. The mechanism of instability is interpreted in terms of an interaction between a plasmon wave and a circuit one under a constraining boundary condition. Properties of the traveling amplification and related problems are discussed, with appropriately suggested semiconductor materials and device designs. The features of the amplifier are a simple structure, a low DC biasing power dissipation for room-temperature operation, unidirectionality, and a wide wavelength range from IR or submillimeter order, suited to various applications.     

Shannon number and degrees of freedom of an image

The problem of the determination of the number of significant degrees of freedom of an image is considered. The equivalence with the Shannon number is shown to hold with a great generality.     

Chiral dynamics with quark degrees of freedom

The possibility to detect DCC fluctuations is discussed. It is shown that interactions with quark background and dissipative effects due to interactions in the chiral field may result in damping of fluctuations. Since the magnitude of fluctuations depends strongly on the initial state and speed of chiral phase transition an accurate evaluation of all modifying processes is required to predict the observability of DCCs.