Long-range interactions

A long-range potential is one whose range, the distance of effective influence, is unbounded or infinite. In this paper we show, using a definition of the range of a potential and certain other theoretical considerations, that the only long-range potential isV(r)=c/r, wherec is a constant.Supported in part by NASA Grant NSG-8035.     

Long-range correlations in hadron-nucleus interactions

An analysis of correlations in rapidity of charged particles produced in proton and antiproton interactions on hydrogen, argon and xenon at 200 GeV is presented. Positive long-range correlations are observed in interactions on heavy targets. The dependence of rapidity correlations between the forward and backward hemisphere on the number of projectile collisions is discussed.     

Long-range Rydberg-Rydberg interactions and molecular resonances

We present a detailed theoretical treatment to describe the lineshape of molecular resonances in a cold dense gas of rubidium Rydberg atoms. Molecular potentials in Hund's case (c) are calculated by diagonalization of an interaction matrix. We show how the strong ℓ-mixing due to long-range Rydberg-Rydberg interactions can lead to resonances in excitation spectra. Such resonances were first reported in [S.M. Farooqi et al., Phys. Rev. Lett. 91, 183002 (2003)], where single UV photon excitations from the 5s ground state occurred at energies corresponding to normally forbidden transitions or very far detuned from the atomic energies. Here, we focus our attention on resonances at energies corresponding to excited atom pairs (n - 1)p_3/2+(n + 1)p_3/2. Very good agreement between the theoretical and experimental lineshapes is found.     

Long-range soliton interactions in dispersion-managed links

A numerical analysis of soliton propagation in a dispersion-compensated transmission system reveals the presence of a small dispersive-wave contribution to the propagating soliton that increases dramatically whenever the input soliton energy is detuned from its optimal value. A straightforward consequence of the dispersive-wave emission is an unexpectedly strong contribution to the long-range soliton-soliton interaction. We show that the combination of long- and short-range interactions induces soliton timing jitter that grows larger than that which arises from the Gordon-Haus effect.     

Long-range interlayer interactions in ferroelectric liquid crystals

Some smectic liquid crystals exhibit a series of phases, including ferroelectric, antiferroelectric, and ferrielectric commensurate structures as well as an incommensurate phase. A long-standing problem has been to understand the origin of the long-range interaction responsible for this rich variety of phases. We study a model that incorporates thermal fluctuations in the flexing of layers and find that it supports commensurate and incommensurate structures. The vibrational entropy competes with an assumed helical interaction between nearest-neighbor layers. An increase in temperature then leads to an unwinding of the helix that proceeds at first through commensurate phases and then into an incommensurate phase. This result is consistent with the experimentally observed "distorted clock model."     

Two-dimensional wave patterns near a Hopf–Wave interaction in a chemical model

The complex behavior of a reaction-diffusion system is investigated in two dimensions near a codimension-2 point between a Hopf and a Wave bifurcation with resonant critical modes. As a result of coupling of a (ω, 0)-mode with modes (ω, k), standing waves arise in an extended region of the control parameters. Near threshold they appear with hexagonal symmetry. The selected wavenumber and the competition of two different spatial scales as a function of the control parameter agree with results calculated from Floquet analysis.     

Long-range spatial correlations in a simple diffusion model

A simple anisotropic diffusion model, according to semiphenomenological arguments, exhibits long-ranged spatial correlations in uniform stationary states.     

Long-range interactions of the chlorine atom

The dispersion interactions of the chlorine atom ground state with atomic hydrogen and itself are computed with a matrix element tabulation derived from the box-based B-spline configuration-interaction method. The matrix element list was also used to calculate the quadrupole and octupole polarisabilities of the chlorine ground state.     

Long-range interactions of excited hydrogen atoms

Accurate calculations are reported of the first and second-order long-range interactions of a hydrogen atom in its ground state and a hydrogen atom in the excited 2s, 2p, 3s, 3p and 3d states. The connections with the spectroscopic states of molecular hydrogen are established. First-order mixing occurs for the n = 3 states and the form of the long-range interaction is complicated.     

Long-range correlations in Boltzmann-Langevin model

The average phase-space density described by the Boltzmann-Langevin model can largely deviate from the one provided by the Boltzmann-Uhling-Uhlenbeck model, due to the non-linear evolution of density fluctuations. This aspect is investigated for long-wavelength, small density fluctuations in the framework of a memory incorporated Boltzmann-Langevin model. It is shown that the correlations associated with density fluctuations yield a collision term describing coupling between the collective vibrations and the single-particle degrees of freedom, which may play an important role in damping of collective motion in both the stable and unstable regions.     

Long-range correlations and ensemble inequivalence in a generalized ABC model

A generalization of the ABC model, a one-dimensional model of a driven system of three particle species with local dynamics, is introduced, in which the model evolves under either (i) density-conserving or (ii) nonconserving dynamics. For equal average densities of the three species, both dynamical models are demonstrated to exhibit detailed balance with respect to a Hamiltonian with long-range interactions. The model is found to exhibit two distinct phase diagrams, corresponding to the canonical (density-conserving) and grand canonical (density nonconserving) ensembles, as expected in long-range interacting systems. The implications of this result to nonequilibrium steady states, such as those of the ABC model with unequal average densities, are briefly discussed.     

Long-range order in a simple model of interacting fermions

We consider a model of spinless fermions on a lattice, interacting through a nearest neighbor repulsion. In the half-filled band case and for dimensionsd 2, we rigorously prove that there is long-range order in some domain of the parameters=(k _B T)^–1 andt/U, wheret is the hopping amplitude of the particles,U the strength of their repulsion, and the inverse temperature. Our technique is based on the usual Peierls argument of classical statistical mechanics but fails for the groundstate. We discuss the specific difficulties introduced by the Fermi statistics.Work supported in part by U.S. NSF grant PHY 90-19433-A02.     

Long-range electron spin-spin interactions from unparticle exchange

Unparticles as suggested by Georgi are identities that are not constrained by dispersion relations but are governed by their scaling dimension d. Their coupling to particles can result in macroscopic interactions between matter that are generally an inverse nonintegral power of distance. This is totally different from known macroscopic forces. We use the precisely measured long-ranged spin-spin interaction of electrons to constrain unparticle couplings to the electron. For 1相似文献   

Higher-order wave interactions in a periodic medium

A singular perturbation analysis of the interaction of the fundamental plane wave progressing in the direction of the sinusoidally varying permittivity of an unbounded medium with the first four space harmonics progressing in the reverse direction is carried out. The periodic inhomogeneity introduces self and mutual interaction phenomena. The self interaction, in general, produces a phase shift and causes the mutual interaction to occur for frequencies higher than those predicted by the Bragg condition. The mutual interaction introduces a complex change in the wavenumber resulting in the interacting waves becoming evanescent. Analytical expressions for the frequency shift and the other wave characteristics in the interaction region are deduced. With the increase in the order of the interaction, the frequency shift becomes a more dominant effect than the wave evanescence.