Can quarks always be confined by a linear potential?

It is demonstrated on the basis of the Dirac equation that quarks cannot be confined by a vector gluon potential of the form(r/r ₀)^a or[ln(r/r ₀]^a, a>0, if the quark-gluon interaction conserves parity. In order to confine quarks with the parity-conserving interaction, the effective gluon potential must be a pseudovector or a scalar. These are shown in a simple Yang-Mills field with theSU(2) group.     

Wave-vector filtering effect of the electric-magnetic barrier in HgTe quantum wells

Because of the helicity of electrons in HgTe quantum wells(QWs) with inverted band structures,the electrons cannot be confined by electric barriers since electrons can tunnel the barriers perfectly without backscattering in the HgTe QWs.This behavior is similar to Dirac electrons in graphene.In this paper,we propose a scheme to confine carriers in HgTe QWs using an electric-magnetic barrier.We calculate the transmission of carriers in 2-dimensional HgTe QWs and find that the wave-vector filtering effect of local magnetic fields can confine the carriers.The confining effect will have a potential application in nanodevices based on HgTe QWs.     

Wave-vector filtering effect of electric–magnetic barrier in HgTe quantum wells

Because of helicity of electrons in HgTe quantum wells (QWs) with inverted band structure, the electrons cannot be confined by electric barriers since electrons can tunnel the barriers perfectly without backscattering in HgTe QWs. This behavior is similar to Dirac electrons in graphene. In this paper, we propose a scheme to confine carriers in HgTe QWs using an electric-magnetic barrier. We calculate the transmission of carriers in 2-dimensional HgTe QWs and find that the wave-vector filtering effect of local magnetic fields can confine the carriers. The confining effect will have potential application in nanodevices based on HgTe QWs.     

Extracting Work Optimally with Imprecise Measurements

Measurement and feedback allows for an external agent to extract work from a system in contact with a single thermal bath. The maximum amount of work that can be extracted in a single measurement and the corresponding feedback loop is given by the information that is acquired via the measurement, a result that manifests the close relation between information theory and stochastic thermodynamics. In this paper, we show how to reversibly confine a Brownian particle in an optical tweezer potential and then extract the corresponding increase of the free energy as work. By repeatedly tracking the position of the particle and modifying the potential accordingly, we can extract work optimally, even with a high degree of inaccuracy in the measurements.     

Application of Hamiltonian of ray motion to room acoustics

Based on a standard Hamiltonian of acoustic ray, it is shown that a ray motion in a finite region can be treated as a particle motion inside a potential well. The boundary reflections of ray can be described by introducing a so-called confining potential to confine a ray motion in a closed domain. It is shown that the square well potential model for the ray motion can reproduce the reverberation time in a two-dimensional room with irregular walls which is consistent with the Norris-Eyring law. It is also shown that the sound reverberation relates the ray chaos of the billiards in polygons with smooth convex walls.     

On a Riemannian method in quantum theory about curved space-time

We start from a given Lorentz metric and a vector field of world lines along which observers and measure devices may move. We describe a procedure to associate one-particle Hilbert spaces and one-particle Hamiltonians to space-like hypersurfaces using a transition to a Riemannian metric. With the aid of suitable boundary conditions one can confine the particle within a world tube (box quantization about curved space-time manifolds).Dedicated to Professor Ivan Úlehla on the occasion of his sixtieth birthday.     

Photon wave-particle duality and virtual electromagnetic waves

The question of the relation between the amplitude of the photon vector potential and its angular frequency is analyzed. The analogy between the relativistic quantum mechanical equations for a massles particle and those governing the photon vector potential appears clearly. Finally, the virtual electromagnetic waves associated with the photon and predicted by de Broglie, Bohr, and other appear naturally as a result of the photon vector potential quantification.     

Integrated photoabsorption strength and sum rules for a bound Dirac particle

Relativistic effects in the integrated total photoabsorption cross section are discussed using a simple model of a Dirac particle bound in a central potential of scalar or vector type. The integrated strength is calculated explicitly and compared to a new relativistic extension of the TRK-sum rule using positive energy projection and to predictions from dispersion relations. M1 and E2 sum rules are also considered. In all cases the integrated strength exceeds the classical sum rule up to a few percent. The dispersion sum rule cannot be compared directly to the integrated strength since it contains a negative contribution from pair production in the potential field which is of the order of a few percent. Whereas the total M1-strength is strongly underestimated by the lowest order M1-sum rule, the total E2-strength is reasonably well reproduced up to about 10% by the lowest order E2-sum rule.     

有限深抛物势量子盘中极化子的激发态性质

量子点作为一种重要的低维纳米结构, 近年来在单光子光源和新型量子点单光子探测器的研究引起了人们的广泛关注, 对各种势阱中量子点性质的研究已取得了重要成果. 但是大多理论研究都局限于无限深势阱, 而有限深势阱更具有实际意义. 利用平面波展开、幺正变换和变分相结合的方法研究了有限深势阱中极化子激发态能量及激发能随势阱形状和量子盘大小的变化规律. 数值计算结果表明: 极化子的激发态能量、激发能随势垒高度或宽度的增大而增大, 原因是势垒愈高、愈宽, 电子穿透势垒的可能性愈小, 电子在阱内运动的可能性愈大, 进而导致极化子的激发态能量和激发能均随势垒高度和宽度的增大而增大; 极化子的激发态能量和激发能随量子盘半径的增大而减小, 表明量子盘具有显著的量子尺寸效应; 极化子的激发态能量随有效受限长度的增加而减小, 原因是有效受限长度愈大, 有效受限强度愈小, 电子受到的束缚愈弱、振动愈慢、势能愈小, 进而导致基态能量、激发态能量减小; 同时由于激发态能量较基态能量减小慢, 使得激发能随之增加. 研究结果对量子点的应用具有一定的理论指导意义.     

The quark bag model with surface tension

A membranous closed surface is introduced to confine colored vector gluon fields in a Lorentz invariant manner. Since the colored pointlike quarks are always coupled to the gluon fields, they become confined inside the closed membrane. The Hamiltonian formulation of the model is presented, and the classical string limit is discussed.     

Formation of porous GaSb compound nanoparticles by electronic-excitation-induced vacancy clustering

Porous semiconductor compound nanoparticles have been prepared by a new technique utilizing electronic excitation. The porous structures are formed in GaSb particles, when vacancies are efficiently introduced by electronic excitation and the particle size is large enough to confine the vacancy clusters. The capture cross section of the surface layer in particles for the vacancies is smaller than that for the interstitials. Under the condition of supersaturation of vacancies in the particle core, porous structures are produced through the vacancy clusters to a void formation.     

Observation of kinetic plasma jets in a coronal-loop simulation experiment

Under certain conditions an intense kinetic plasma jet is observed to emerge from the apex of laboratory simulations of coronal plasma loops. Analytic and numerical models show that these jets result from a particle orbit instability in a helical magnetic field whereby magnetic forces radially eject rather than confine ions with sufficiently large countercurrent axial velocity.     

Local one particle approximation of the current commutators

The spectral functions of the current commutators matrix elements between vacuum and one particle boson states are calculated in a local one particle approximation. In the equal time limit, the restrictions imposed by the current algebra commutation relations without operator Schwinger terms are systematically discussed. It is found, that in this approximation, and when one of the currents is conserved, the PCAC and vector meson dominance models cannot be considered simultaneously. The comparison of the results with experiment gives preference to the first of the two models.     

On the Electromagnetic Origin of Inertia and Inertial Mass

We address the problem of inertial property of matter through analysis of the motion of an extended charged particle. Our approach is based on the continuity equation for momentum (Newton’s second law) taking due account of the vector potential and its convective derivative. We obtain a development in terms of retarded potentials allowing an intuitive physical interpretation of its main terms. The inertial property of matter is then discussed in terms of a kind of induction law related to the extended charged particle’s own vector potential. Moreover, it is obtained a force term that represents a drag force acting on the charged particle when in motion relatively to its own vector potential field lines. The time rate of variation of the particle’s vector potential leads to the acceleration inertia reaction force, equivalent to the Schott term responsible for the source of the radiation field. We also show that the velocity dependent term of the particle’s vector potential is connected with the relativistic increase of mass with velocity and generates a longitudinal stress force that is the source of electric field lines deformation. In the framework of classical electrodynamics, we have shown that the electron mass has possibly a complete electromagnetic origin and the obtained covariant equation solves the “4/3 mass paradox” for a spherical charge distribution.     

Conserved Gross–Pitaevskii equations with a parabolic potential

An integrable Gross–Pitaevskii equation with a parabolic potential is presented where particle density ∣u∣² is conserved. We also present an integrable vector Gross–Pitaevskii system with a parabolic potential, where the total particle density ${\sum }_{j=1}^{n}| {u}_{j}{| }^{2}$ is conserved. These equations are related to nonisospectral scalar and vector nonlinear Schrödinger equations. Infinitely many conservation laws are obtained. Gauge transformations between the standard isospectral nonlinear Schrödinger equations and the conserved Gross–Pitaevskii equations, both scalar and vector cases are derived. Solutions and dynamics are analyzed and illustrated. Some solutions exhibit features of localized-like waves.     

Cauchy problem on the plane for the dispersionless Kadomtsev-Petviashvili equation

We construct the formal solution to the Cauchy problem for the dispersionless Kadomtsev-Petviashvili equation as an application of the inverse scattering transform for the vector field corresponding to a Newtonian particle in a time-dependent potential. This is in full analogy with the Cauchy problem for the Kadomtsev-Petviashvili equation, associated with the inverse scattering transform of the time-dependent Schrödinger operator for a quantum particle in a time-dependent potential.     

Observation of inhomogeneous spectral broadening of stimulated brillouin scattering in an optical fiber

We report experimental results which show that the stimulated Brillouin scattering (SBS) spectrum in an optical fiber is inhomogeneous, exhibiting spectral broadening and hole burning under cw monochromatic laser excitation. This phenomenon arises from the waveguide interaction of the pump and Stokes signals and is a fundamental property of SBS in waveguiding systems due to their ability to confine a fan of radiation wave vector directions.     

Macro-scale observation of curl-free vector potential: A manifestation of quantum modulation of the de Broglie wave

Experimental results are presented here reporting the detection of a curl-free vector potential on the macro-scale as contrasted with the detection on the micro-scale à la Aharonov-Bohm. Such a detection is attributed to the ‘quantum modulation’ of the plane wave state of the guiding centre motion of a charged particle in a magnetic field, which is generated concomitantly with the excitation of its Landau levels in a scattering episode, through the mechanism of quantum entanglement between the parallel and perpendicular degrees of freedom of the particle. Such a ‘quantum modulation’ is also a matter wave, but on the macro-scale, and leads to the ‘sensing’ of the curl-free vector potential on the macro-scale. Thus while the Aharonov-Bohm effect is attributed to the sensing of the curl-free vector potential by the de Broglie wave, its sensing on the macro-scale is attributed to the modulation of the de Broglie wave.     

Multiple trapping using a focused hybrid vector beam

We propose a simple and efficient method that uses a single focused hybrid vector beam to confine metallic Rayleigh particles at multiple positions.We study the force mechanisms of multiple trapping by analyzing the gradient and scattering forces.It is observed that the wavelength and topological charges of the hybrid vector beam regulate the trapping positions and number of optical trap sites.The proposed method can be implemented easily in three-dimensional space, and it facilitates both trapping and organization of particles.Thus, it can provide an effective and controllable means for nanoparticle manipulation.     

Confinement limit of a Dirac particle in two and three dimensions

Consider a particle that is in a stationary state described by the Dirac equation with a finite-range potential. In two and three dimensions the particle can be confined to an arbitrarily small spatial region. This is in contrast to the one-dimensional case in which the confinement region cannot be much narrower than the Compton wavelength.