bluuebunny/crossref_metadata_2025 huggingface dataset:
On the theory of ion transfer rates across the interface of two immiscible liquids
Authors: Marcus R. A.
Published: July 2002

Ion transfer across the interface of two immiscible liquids involves a mechanism for initiating desolvation from the first liquid, A, and concerted solvation by the second, B. In the present article a mechanism is considered in which this initiation is facilitated by the ion attaching itself to the tip of a solvent protrusion of B into A. (Protrusions have been observed in computer simulations and termed “fingers” or “cones.”) It is presumed that the most effective protrusion represents a balance between two opposing effects: the more convex the protrusion the less probable the ion/protrusion formation but also the less the resistance to extrusion of the intervening liquid between the ion and the surface. An analogy of the latter to hydrodynamics is noted, namely, the more convex the surface the less the frictional force it exerts on the approaching ion. After diffusion in coordinate and solvation space across the interfacial region, the final detachment of the ion from solvent A is assumed to occur from a protrusion of A into B. Existing data on ion transfer rates are discussed, including the question of diffusion vs kinetic control. Computer simulations that correspond to the experimental conditions in realistic liquids for measurement of the electrochemical exchange current rate constant k0 are suggested. They can be used to test specific theoretical features. With a suitable choice of systems the need (and a major barrier to the simulations) for having a base electrolyte in such simulations can be bypassed. An experiment for the real-time observation of an ion leaving the interface is also suggested.
Photodissociation dynamics of the triiodide anion (I3−)
Authors: Choi Hyeon , Bise Ryan T. , Hoops Alexandra A. , Neumark Daniel M.
Published: July 2002

The spectroscopy and dissociation dynamics of I3− were investigated using fast beam photofragment translational spectroscopy. The photofragment yield of I3− from 420 to 240 nm was measured, yielding two broadbands at the same energies as in the absorption spectrum of I3− in solution. Photodissociation dynamics measurements performed with two-particle time-and-position sensitive detection revealed two product mass channels having photofragment mass ratios of 1:2 and 1:1. Both channels were seen at all photolysis wavelengths. Translational energy distributions show that the 1:2 products are from a combination of I(2P3/2)+I2− and I*(2P1/2)+I2−. The 1:1 mass channel is from symmetric three-body dissociation to I−+2I.
Collectivity and geometry. IV. Sp(6) ⊇ Sp(2)×O(3) basis states for open shells
Authors: Moshinsky M. , Nicolescu M. , Sharp R. T.
Published: July 2002

Using generating function methods, branching rules for Sp(6) ⊇ Sp(2)×O(3) are derived. The branching rules suggest an integrity basis, or set of elementary permissible diagrams, in terms of which the subgroup basis states are defined; they correspond to vibrational, or Bohr–Mottelson type, states in the nuclear symplectic model.
Reciprocal relations for effective conductivities of anisotropic media
Authors: Nevard John , Keller Joseph B.
Published: July 2002

Any pair of two-dimensional anisotropic media with local conductivity tensors that are functions of position and that are related to one another in a certain reciprocal way are considered. It is proved that their effective conductivity tensors are related to each other in the same way for both spatially periodic media and statistically stationary random media. An inequality involving the effective conductivity tensors of two three-dimensional media that are reciprocally related is also proved. These results extend the corresponding results for locally isotropic media obtained by Keller, Mendelsohn, Hansen, Schulgasser, and Kohler and Papanicolau. They also yield a relation satisfied by the effective conductivity tensor of a medium reciprocal to a translated or rotated copy of itself.
On the polynomial solutions of ordinary differential equations of the fourth order
Authors: Dehesa J. S. , Buendia E. , Sanchez-Buendia M. A.
Published: July 2002

The density of zeros of polynomial solutions of ordinary differential equations of the fourth order with coefficients depending only on the independent variable is analyzed. The first four moments of such a density are given directly in terms of the coefficients which characterize the differential operator. Application to the nonclassical orthogonal polynomials corresponding to the names Krall–Legendre, Krall–Laguerre, and Krall–Jacobi is done. Global asymptotic properties of the zeros of these polynomials are also obtained.
Time-dependent invariant associated to nonlinear Schrödinger–Langevin equations
Authors: Nassar Antônio B.
Published: July 2002

Via the quantum-hydrodynamical method, a time-dependent invariant associated to the quantum dissipative time-dependent harmonic oscillator (TDHO), described by two classes of nonlinear Schrödinger–Langevin equations with the following frictional nonlinear terms is constructed: (i) W1=−iℏν(ln ψ−〈ln ψ〉), which is the Schuch–Chung–Hartman frictional nonlinear term, and (ii) W2=ν{[x−〈x〉][cp̂+(1−c)〈 p̂〉]− 1/2 iℏc}, which includes the Süssmann (c=1), the Hasse (c= 1/2 ), and the Albrecht–Kostin (c=0) frictional nonlinear operators. The associated invariant found is exact for the Schuch–Chung–Hartman and Hasse models, and only approximate for the Süssman and Albrecht–Kostin models.
Forces and the existence of stresses in invariant continuum mechanics
Authors: Segev Reuven
Published: July 2002

In an invariant formulation of pth-grade continuum mechanics, forces are defined as elements of the cotangent bundle of the Banach manifold of Cp embeddings of the body in space. It is shown that forces can be represented by measures which generalize the stresses of continuum mechanics. The mathematical representation procedure makes the restriction of forces to subbodies possible. The local properties of the stress measures are examined. For the case where stresses are given in terms of smooth densities, it is shown that the structure of forces agrees with the form of forces one assumes in the traditional formulation, and the equilibrium differential equations are obtained.
The effect of a one-dimensional potential of finite range on the statistical parameters of an incident ensemble of particles. II. Localized states
Authors: Farina J. E. G.
Published: July 2002

If an ensemble of particles moving parallel to the x axis in the positive direction impinges on a piecewise continuous potential confined to the interval [−a,a] (a>0) it will divide into a transmitted ensemble and a reflected ensemble. It is shown that the classical results for the means, variances, and covariance of position and velocity of the transmitted and reflected ensembles hold in quantum mechanics if the position and momentum probability densities of the incident ensemble are assumed to be sufficiently localized, both in momentum and position. It is also assumed that the support of the probability density of momentum is bounded and positive, and on it the moduli and arguments of the transmission and reflection coefficients are sufficiently well behaved.
The Heisenberg–Weyl group in the coherent state basis and the Bargmann transform
Authors: Basu Debabrata , Kar T. K.
Published: July 2002

It is shown that the representation matrices of the quantum mechanical group in the coherent state basis can be used as bases for the expansion of arbitrary square integrable functions on the group. Although this basis is nonorthogonal the expansion can be inverted in a manner similar to an orthogonal basis. Next a coherent state ‘‘wave function’’ is defined in analogy with the Schrödinger wave function and the above matrix elements are used to determine the action of the group in the space of the coherent state wave functions. The function space in this realization is Bargmann’s Hilbert space of analytic functions. It is shown that the mixed basis matrix element between the coordinate and coherent state bases is essentially the integral kernel of Bargmann. The transpose of this matrix element yields the kernel for the inversion of the transform. In this construction the Bargmann transform appears as the unitary transformation connecting the Schrödinger and coherent state wave functions. This considerably simplifies Bargmann’s original arguments and yields the integral transform as well as its inversion formula in a simple way.
Singular anharmonicities and the analytic continued fractions
Authors: Znojil M.
Published: July 2002

The potential V(r)=μ2r2+λ2r−4 is investigated and its bound states are constructed by a generalized Hill-determinant method. It is shown that the binding energy E and another free parameter χ (in the underlying Laurent-series representation of the wave function) may be obtained from a coupled pair of Hill-determinant equations.
Infrared and vacuum structure in two-dimensional local quantum field theory models. The massless scalar field
Authors: Morchio G. , Pierotti D. , Strocchi F.
Published: July 2002

A systematic and rigorous treatment of the massless scalar field in two dimensions is presented by carefully taking into account the maximal (Krein) state space associated to the Wightman functions. This allows a simple and rigorous answer to controversial statements appearing in the literature about the uniqueness of the translation-invariant state, the construction of translation-invariant operators (infrared operators), the scale and special conformal transformations of the fields, the construction of the dual field and the breaking of the Lorentz transformations, and, more generally, the status of symmetry breaking in the model.
Variational and perturbative schemes for a spiked harmonic oscillator
Authors: Aguilera-Navarro V. C. , Estévez G. A. , Guardiola R.
Published: July 2002

A variational analysis of the spiked harmonic oscillator Hamiltonian operator −d2/ dx2+x2+l(l+1)/x2+λ‖x‖−α , where α is a real positive parameter, is reported in this work. The formalism makes use of the functional space spanned by the solutions of the Schrödinger equation for the linear harmonic oscillator Hamiltonian supplemented by a Dirichlet boundary condition, and a standard procedure for diagonalizing symmetric matrices. The eigenvalues obtained by increasing the dimension of the basis set provide accurate approximations for the ground state energy of the model system, valid for positive and relatively large values of the coupling parameter λ. Additionally, a large coupling perturbative expansion is carried out and the contributions up to fourth-order to the ground state energy are explicitly evaluated. Numerical results are compared for the special case α=5/2.
Large family of colliding waves in the Einstein–Maxwell theory
Authors: Halilsoy Mustafa
Published: July 2002

A general class of similarity integrals of the Ernst equation with the method of Chandrasekhar and Xanthopoulos are combined to obtain a family of solutions for colliding waves in the Einstein–Maxwell theory. The family is parametrized by an arbitrary harmonic function that satisfies the Euler–Darboux equation. The first nontrivial member of the family is shown to be the cross-polarized version of the Bell–Szekeres solution.
Parasupercoherent states and color supergroups
Authors: Debergh N.
Published: July 2002

Parabosonic coherent states are illustrated from the displacement operator point of view. Such a construction requires the use of the Green–Cusson Ansätze, a specific representation of parastatistics, leading to color supergroups. A comparison with a previous result is shown through the annihilation operator and the minimum uncertainty contexts. The extension to the parasupersymmetric case is also considered.
Regularization dependence of vacuum energy in arbitrarily shaped cavities
Authors: Cognola Guido , Vanzo Luciano , Zerbini Sergio
Published: July 2002

The vacuum energy for a free scalar field in the case of an arbitrarily shaped cavity is discussed. A complete analysis of the divergences is presented and some regularization schemes are analyzed in some detail. The vacuum energy for a free scalar field defined on an ultrastatic three-dimensional space-time R×𝒮, 𝒮 being a compact Riemann surface of genus greater than unity, is explicitly computed using the Selberg trace formula. As a result, a negative vacuum energy is found.
Quantization of a four-dimensional generally covariant conformal model
Authors: Ragiadakos C. N.
Published: July 2002

A four-dimensional generally covariant action, which depends on the complex structures of the Hermitian space-times, is studied. It is also invariant under a gauge group and independent Weyl transformations of the vierbein. These symmetries render it formally renormalizable. It is quantized using the (Dirac) canonical and the BRS quantization procedures. An approximative expansion of the vierbein around background Hermitian manifolds permits explicit calculations. Hermitian manifolds, satisfying trivial reality conditions (z0 = z̄ 0, z0̃ = z̄ 0̃, z1̃ = z̄ 1), cannot be such background manifolds, because the first approximation of the BRS charge is not nilpotent for any number of gauge fields. On the other hand, the expansion may be performed around the Kerr–Newman manifold only if its mass, charge, and angular momentum satisfy a precise relation.
Geometric superalgebra and the Dirac equation
Authors: Keller Jaime , Rodríguez Adán
Published: July 2002

A unified mathematical approach to spinors and multivectors or superalgebra is constructed in a form useful to study the mathematical description of matter and its interaction fields. The formalism then encompasses both points of view: multivectors for the description of (space-time) geometry and the description of the integer spin, interaction fields, and spinor representations suitable for the description of half odd integer, matter fields. An application is made to study the change of the Dirac equation under the spinors to multivectors (to scalars) mapping. The physical and geometric content of the multivector solutions of the Dirac–Hestenes equation is clearly shown.
Embedding problem. II
Authors: Ozsváth István
Published: July 2002

In this paper all the subfamilies of the homogeneous spaces described in the Introduction which can be embedded into a five-dimensional sphere are described.
Isometry groups of three-dimensional Riemannian metrics
Authors: Bona Carles , Coll Bartolomé
Published: July 2002

The necessary and sufficient conditions for a three-dimensional Riemannian metric to admit a group Gr of isometries acting on s-dimensional orbits are given. This provides the list of (abstract) groups that can act isometrically and maximally on such metrics. The conditions are expressed in terms of the eigenvalues and eigenvectors of the Ricci tensor. In any case, the order of differentiability of these data necessary to determine the isometry group is less than 4.
Dirac equation in external fields: Separation of variables in nondiagonal metrics
Authors: Shishkin German V. , Cabos William D.
Published: July 2002

The algebraic method of separation of variables in the Dirac equation proposed in earlier works by one of the present authors [Theor. Math. Phys. 70, 204 (1987); J. Math. Phys. 30, 2132 (1989)] is developed for the space-time with nondiagonal metrics. The essence of the method consists of the separation of the first-order matricial differential operators that define the dependence of the Dirac’s bispinor on the related variables. In contrast to some other authors the pairs of operators are commuted on each step of separation including the variables mixed by nondiagonal elements of fundamental tensor of space-time. There are reasons to believe that it must be some local similarity transformation connected these commuted operators with noncommuted corresponding operators of other authors, although such transformation in view of mathematical difficulties of problem, in general, were not successfully found.
Derivation of correlation spectra by the operator algebra technique
Authors: Song Jong June , Yi Sam Nyung , Choi Sang Don
Published: July 2002

Cross and autocorrelation spectra are dealt with in a unified category by a straightforward method, which is called the operator algebra technique. In this technique the Laplace transform of the correlation functions is performed prior to calculating the Liouville operators. It is shown that this derivation procedure is very simple and the results are identical with those of some other authors.
Spinor and vector representations in four-dimensional Grassmann space
Authors: Mankoc̆-Bors̆tnik Norma
Published: July 2002

Spinor, scalar, and vector irreducible representations of generators of the Lorentz transformations in a four-dimensional Grassmann subspace of a d-dimensional Grassmann space are studied. For d=5 there are four spinor representations with the properties of Majorana spinors and two scalar, two three-vector and two four-vector representations with the properties of bosons, offering the possibility of the canonical quantization of not only bosonic but also fermionic fields.
The interaction potential of the stationary measure of a high-noise spinflip process
Authors: Maes Christian , Velde Koen Vande
Published: July 2002

A continuous time spinflip process, started from an arbitrary state, is proven to yield a Gibbs state after any time t≳0 if the noise is high enough. This is done by approximating the process by discrete time processes. The relative energies of those Gibbs states are constructed explicitly via a high-noise cluster expansion.
The quantum relativistic harmonic oscillator: Spectrum of zeros of its wave functions
Authors: Zarzo A. , Martínez A.
Published: July 2002

The distribution of zeros of the wave functions of the quantum relativistic harmonic oscillator is studied. An analytic approximate expression for this distribution is derived within the framework of the WKB approximation. Using potential theory techniques, it is proved that this WKB approach gives the right asymptotic distribution, which is explicitly calculated.
Boson fermion realizations for the super-rotation algebra
Authors: Daumens Michel
Published: July 2002

The dispin realization of the super-rotation, in terms of two fermion pairs of creation and annihilation operators is presented. A short review of other fermion boson realizations of this algebra is given as well as their correspondence with differential operator realizations.
The semiclassical limit of the two-dimensional quantum Yang–Mills model
Authors: King Christopher , Sengupta Ambar
Published: July 2002

The semiclassical limit of the quantum Yang–Mills partition function on a compact oriented surface is related to the symplectic volume of the moduli space of flat connections, by using an explicit expression for the symplectic form. This gives an independent proof of some recent results of Witten and Forman.
Torsion and Weyl convector in metric-affine models of gravity
Authors: Macías Alfredo , Mielke Eckehard W. , Morales-Técotl Hugo A. , Tresguerres Romualdo
Published: July 2002

In this work, we analyze the projective transformations of nonlinear curvature scalar Lagrangians and show that only the Weyl covector piece of the nonmetricity and the vector part of the torsion are affected by these transformations in an opposite manner. It is pointed out that, since the Dirac equation couples only to the axial piece of the torsion, it is projectively invariant. Moreover, we look at a generalized topological 3D gravity by supplementing a translational Chern–Simons term. We obtain an exact solution, with a conformal de Sitter background which implys that, for very large times, Poincaré invariance becomes exact.
The space of Lie algebra 2-cocycles of an affine transformation group
Authors: Harnett G.
Published: July 2002

In this paper we present the intrinsic structure of the space of Lie algebra 2-cocycles of an affine transformation group. An equivariant morphism from this space into a space of quadratic maps on the affine space is constructed. Under this morphism, the 2-cocycles of the Galilei Lie algebra correspond to certain affine tensor fields on Galilean space–time.
The L-S coupling revisited: A general solution for the 4 electron system
Authors: Iommi Amunátegui G.
Published: July 2002

The relation between the unitary group SU(n) and the symmetric group Sn is treated using the induced characters of Sn. By means of this approach the L-S coupling for four electrons is solved.
Gauging discrete symmetries
Authors: McInnes Brett
Published: July 2002

Recent developments in quantum gravity theory have led to the suggestion that various discrete symmetries, in particular charge–parity (CP), should be ‘‘gauged,’’ that is, interpreted as elements of some connected Lie group. As the parity operator is related to a space–time isometry, however, it is far from clear that this suggestion has any real meaning. We give a simple geometric construction in terms of which it is meaningful to ‘‘gauge’’ discrete symmetries, provided that certain nontrivial conditions are satisfied by the space–time manifold, by the gauge group, and by the discrete symmetry itself.
Gauge fields on the quantum net
Authors: Selesnick S. A.
Published: July 2002

We continue our study of the quantum net, at a coarser resolution than previously. We adapt and extend various ideas of Finkelstein to delineate the structure of the space of defects, and develop a formal dynamics along the lines of the Schwinger action principle. Formal variation of the defect and the application of the correspondence principle developed earlier lead immediately to macroscopic continuum Lagrangian densities taking the form of power series in the net constant, whose lowest-order terms reproduce exactly (up to constant factors): the Yang–Mills form, plus the Feynman gauge fixing term, for SU(2) and SU(3) gauge theories, and the Einstein–Hilbert form for gravity. The algebraic manipulations, though formal, are entirely elementary. The theory is, as yet, local, unghosted, and not second-quantized. No U(1) gauge symmetry, or Higgs-like field, is apparent.
Classical deformations, Poisson–Lie contractions, and quantization of dual Lie bialgebras
Authors: Ballesteros A. , Herranz F. J. , del Olmo M. A. , Santander M.
Published: July 2002

A Poisson–Hopf algebra of smooth functions is simultaneously constructed on the two dimensional Euclidean, Poincaré, and Heisenberg groups by using a classical r-matrix which is invariant under contraction. The quantization for this algebra of functions is developed, and its dual Hopf algebra is also computed. Contractions on these quantum groups are studied. It is shown that, within this setting, classical deformations are transformed into quantum ones by Hopf algebra duality and the quantum Heisenberg algebra is derived by means of a (dual) Poisson–Lie quantization that deforms the standard Moyal–Weyl *ℏ-product.
Greechie diagrams, nonexistence of measures in quantum logics, and Kochen–Specker-type constructions
Authors: Svozil K. , Tkadlec J.
Published: July 2002

We use Greechie diagrams to construct finite orthomodular lattices ‘‘realizable’’ in the orthomodular lattice of subspaces in a three-dimensional Hilbert space such that the set of two-valued states is not ‘‘large’’ (i.e., full, separating, unital, nonempty, resp.). We discuss the number of elements of such orthomodular lattices, of their sets of (ortho)generators and of their subsets that do not admit a ‘‘large’’ set of two-valued states. We show connections with other results of this type.
Classical and quantum implications of the causality structure of two-dimensional space–times with degenerate metrics
Authors: Gratus Jonathan , Tucker Robin W.
Published: July 2002

The causality structure of two-dimensional manifolds with degenerate metrics is analyzed in terms of global solutions of the massless wave equation. Certain novel features emerge. Despite the absence of a traditional Lorentzian Cauchy surface on manifolds with a Euclidean domain, it is possible to uniquely determine a global solution (if it exists), satisfying well-defined matching conditions at the degeneracy curve, from Cauchy data on certain spacelike curves in the Lorentzian region. In general, however, no global solution satisfying such matching conditions will be consistent with this data. Attention is drawn to a number of obstructions that arise prohibiting the construction of a bounded operator connecting asymptotic single particle states. The implications of these results for the existence of a unitary quantum field theory are discussed.
On the effect of pruning on the singularity structure of zeta functions
Authors: Dahlqvist Per
Published: July 2002

We investigate the topological zeta function for unimodal maps in general and dynamical zeta functions for the tent map in particular. For the generic situation, when the kneading sequence is aperiodic, it is shown that the zeta functions have a natural boundary along its radius of convergence, beyond which the function lacks analytic continuation. We make a detailed study of the function ∏n=0∞(1−z2n) associated with sequences of period doublings. It is demonstrated that this function has a dense set of singular points and zeros on the unit circle, exhibiting a rich number theoretical structure.
Standard forms of local nets in quantum field theory
Authors: Thomas Launey J. , Wichmann Eyvind H.
Published: July 2002

Nets of von Neumann algebras, with local algebras associated with all compact, convex, causally complete subsets of spacetime, are constructed, assuming a particular kind of net considered by Bisognano and Wichmann. The properties of such nets are discussed, within the general framework of algebraic quantum field theory, with an emphasis on the relation between the geometry of spacetime and the structure of the nets. An “intersection property” for the local algebras is stated and proved. The structure of subnets of such nets is discussed. A number of particular possible features of the nets are shown to be hereditary in the sense that the subnets have the same features. Possible further extensions of the domain of definition of these nets are discussed briefly.
Two algebraic properties of thermal quantum field theories
Authors: Jäkel Christian D.
Published: July 2002

We establish the Schlieder and the Borchers property for thermal field theories. In addition, we provide some information on the commutation and localization properties of projection operators.
On the effect of adding ε-Bernoulli percolation to everywhere percolating subgraphs of Zd
Authors: Benjamini Itai , Häggström Olle , Schramm Oded
Published: July 2002

We show that adding ε-Bernoulli percolation to an everywhere percolating subgraph of Z2 results in a graph which has large scale geometry similar to that of supercritical Bernoulli percolation, in various specific senses. We conjecture similar behavior in higher dimensions.
Fractional supersymmetry and Fth-roots of representations
Authors: Rausch de Traubenberg M. , Slupinski M. J.
Published: July 2002

A generalization of super-Lie algebras is presented. It is then shown that all known examples of fractional supersymmetry can be understood in this formulation. However, the incorporation of three-dimensional fractional supersymmetry in this framework needs some care. The proposed solutions lead naturally to a formulation of a fractional supersymmetry starting from any representation 𝒟 of any Lie algebra g. This involves taking the Fth-roots of 𝒟 in an appropriate sense. A fractional supersymmetry in any space–time dimension is then possible. This formalism finally leads to an infinite dimensional extension of g, reducing to the centerless Virasoro algebra when g=sl(2,R).
Thermal conductivity of anisotropic HTS crystals YBa2Cu3O7−x and Bi2Sr2CaCu2O8+y
Authors: Efimov V. B. , Mezhov-Deglin L. P.
Published: July 2002

The results of measurements of thermal conductivity κ and resistivity ρ of some superconducting crystals of YBa2Cu3O7−x and Bi2Sr2CaCu2O8+y in the ab plane (κab and ρab) and along the c axis (κc and ρc) are presented. The magnitudes and temperature dependences of the thermal conductivity of Y- and Bi-crystals are found to be close and to vary less significantly than the resistance of samples of the same composition. In contrast to the predictions of the electron heat transport theory in HTS cuprate crystals, the relative height of the peaks in κab(T)/κab(Tc) curves becomes equal to two in highly anisotropic Bi-samples, and the peak is displaced toward lower temperatures Tm<0.4Tc with increasing value of this ratio, as well as in Y-crystals which have a lower anisotropy. All these facts indicate that in theoretical calculations of the thermal conductivity of layered HTS crystals in the ab plane at temperatures below Tc, the possibility of an increase in the electron and the phonon components of thermal conductivity must be taken into consideration, as in calculations of thermal conductivity of perfect crystals of conventional metallic superconductors. In the direction perpendicular to the layers, the thermal conductivity κc≪κab and decreases monotonically with temperature. The contribution from the electron component to κc can be disregarded.
New modes of coupled electron–ripplon oscillations in a Wigner crystal in strong driving electric fields
Authors: Sivokon’ V. E. , Dotsenko V. V. , Kovdrya Yu. Z. , Grigor’ev V. N.
Published: July 2002

Resonant peculiarities in the conductivity of a Wigner crystal with a surface charge density 6×108cm−2 as functions of the amplitude of an exciting signal are investigated at temperature 75 mK in the frequency range 1–20 MHz. It is found that an increase in the signal amplitude induces new resonances which probably are due to coupling of phonon modes of the electron crystal with the modes of capillary waves excited under nonlinear conditions.
Effect of reduced gravity and weightlessness on vapor bubble dynamics and heat transfer in boiling liquid
Authors: Rusanov K. V. , Shcherbakova N. S.
Published: July 2002

The results on boiling of liquids and gas bubbling under simulated long-term reduced gravity are reported. The possibility of extrapolating these results to the real spacecraft conditions is considered and the program of on-board space experiments is proposed to test the current theory at the relative accelerations 10−4–10−6 which are unattainable in a laboratory. Tests in free-fall towers, in aircraft, or in ballistic rockets are inadequate since only prolonged (over one hour) experiments in the Earth’s orbit can provide reliable data. The advantage of cryogenic liquids, helium, in particular, in space experiments is discussed.
Low-temperature plasticity of Pb–Bi alloys: the role of thermal activation and inertial effects
Authors: Isaev N. V. , Natsik V. D. , Pustovalov V. V. , Fomenko V. S. , Shumilin S. E.
Published: July 2002

Detailed studies of temperature dependences of critical shear stress and strain-rate sensitivity of deforming stress of Pb–Bi single crystals with 0.1–6.0 at. % Bi are carried out in the temperature range 0.5–295 K. The deforming stress decrease during a superconducting transition of the sample is studied and the concentration dependence of the effect is measured. The ideas of a gradual transition (upon cooling) from thermally activated motion of dislocations through impurity barriers to the thermoinertial mechanism in the temperature range 10–25 K and further to the quantum-inertial motion at temperatures ≲1 K are developed. A detailed thermoactivation analysis of experimental data is carried out, and empirical estimates of internal stresses, dislocation–impurity interaction parameters, electron and phonon components of dynamic drag coefficient for dislocations are obtained.
Linear electron chains on the surface of superfluid helium
Authors: Kovdrya Yu. Z. , Nikolaenko V. A. , Gladchenko S. P. , Sokolov S. S.
Published: July 2002

A unique one-dimensional system of linear electron chains on the liquid helium surface is realized experimentally for the first time. This system is created by using the distortion of the helium surface and covering the profiled dielectric substrate in a confining electric field holding electrons in the liquid channels being formed. The carrier mobility in linear electric chains is measured in the temperature interval 0.5–1.8K in confining fields up to 1 kV/cm. It is shown that the electron mobility depends on the purity of the substrate surface. For clean substrates, the mobility increases with decreasing temperature in the entire investigated temperature range. The results of measurements are found to be in accord with the existing theory.
On the theory of phase separation in systems metallized as a result of doping
Authors: Ivanov M. A. , Loktev V. M.
Published: July 2002

The mechanism of formation of an inhomogeneous ground state of weakly doped systems, consisting of the domains of metallic and insulating phases, is proposed. According to this mechanism, the formation of the charge-neutral metallic regions with the highest possible concentration of free charge carriers (and hence of the dopants generating them) is shown to be thermodynamically advantageous.
Thermal expansion of single-crystal fullerite C60 at liquid-helium temperatures
Authors: Aleksandrovskii A. N. , Esel’son V. B. , Manzhelii V. G. , Udovidchenko B. G. , Soldatov A. , Sundqvist B.
Published: July 2002

The thermal expansion of single-crystal fullerite C60 has been studied in the range of liquid-helium temperatures (2–10 K). At temperatures below ∼4.5 K the thermal expansion of fullerite C60 becomes negative, in agreement with the previous results on polycrystalline materials. A qualitative explanation of the results is proposed.
Dislocation drag in the low-temperature phase of C60 fullerite due to orientational relaxation of the molecules
Authors: Natsik V. D. , Podol’skiı̆ A. V.
Published: July 2002

The interaction of edge dislocations with pentagonal (p) and hexagonal (h) orientation states of the molecules in the low-temperature simple cubic phase of C60 fullerite is discussed. The temperature interval considered is Tg<T<Tc, where Tc=260 K is the phase transition temperature and Tg=90 K is the orientational glass point. The nonuniform distribution of the h configurations around a sessile dislocation line is described, and the starting force Fs(T) needed to break the dislocation away from the cloud of h configurations formed by it is determined. The dynamic drag force FD(T,V) arising as a result of thermally activated transitions between the p and h configurations under the influence of the elastic field of a dislocation moving at a constant velocity V is calculated and analyzed.
Bubbles in a Hele–Shaw cell: Numerical simulation of three-dimensional effects
Authors: Meiburg E.
Published: July 2002

Time-dependent numerical simulations of immiscible bubbles propagating in a Hele–Shaw cell are presented. Purely two-dimensional calculations only show elongated bubbles propagating faster than the viscous fluid, in agreement with Tanveer’s results. For small capillary numbers, these bubbles assume circular shapes while their velocity approaches a plateau. By including the leading-order three-dimensional effects on the pressure jump across the interface, wider and shorter bubbles migrating at smaller velocities can be observed. In particular, flattened bubbles and bubbles slower than the viscous phase are found. Even though these bubbles also approach circular shapes for high surface tension values, a velocity plateau is not observed. While noticing that the three-dimensional effects promote a tip instability, the multiple shapes and transitioins observed experimentally can only be partially explained.
Internal solitary waves in a two-fluid system
Authors: Mirie Rida M. , Pennell Stephen A.
Published: July 2002

A ninth-order perturbation solution describing the solitary wave at the interface of a two-fluid system is found by means of a symbolic manipulation software package. The coefficients in the general solution are evaluated for 37 values of the density and depth ratios σ and R, yielding the first nine terms in the series expansions for the wave profile, wave speed, mass, and potential energy in powers of the wave amplitude a. A maximum in the ninth-order partial sum for the wave speed is found in each case for which the sum is judged to be an acceptable approximation to the infinite series for all a less than or equal to Af=(R−(σ)1/2 )/(1+(σ)1/2). Furthermore, this maximum occurs for a value of a very close to the value of Af. In all 37 cases, the [5,4] Padé approximant for the wave speed has a maximum, and in almost all cases the maximum occurs close to Af. No maximum is found in the ninth-order partial sums for mass or potential energy in the range of values of a for which these sums are judged to be valid.
Energy transfer in turbulence
Authors: Treviño George
Published: July 2002

It is theoretically established that energy transfer in nonhomogeneous turbulence occurs in two distinct scale-independent ‘‘modes.’’ The physical significance of these modes is examined. Further, evidence is presented that suggests the existence of a conservation principle that governs the transfer of energy between turbulence eddies of differing size. A possible algebraic form of such a principle is formulated.
Axisymmetric shapes and stability of isolated charged drops
Authors: Basaran O. A. , Scriven L. E.
Published: July 2002

Axisymmetric equilibrium shapes and stability of isolated charged drops are found by solving simultaneously the Young–Laplace equation for surface shape and the Laplace equation for the electric field. Families of two-, three-, and four-lobed shapes that branch from the trunk family of spheres are treated systematically by means of the Galerkin/finite element method and a tessellation that deforms with the free surface. The results show that at the limit found by Rayleigh in 1882 the spherical family exchanges stability with a family of two-lobed shapes, a transcritically bifurcating family, one arm of which proves to consist of stable shapes. The results are reinforced by those of approximating the stable drop shapes as oblate spheroids. Thus oblate drops carrying charge in excess of the Rayleigh limit ought to be seen in experiments, though none have yet been reported.
Nonlinear and dispersive effects in Kelvin waves
Authors: Tomasson G. G. , Melville W. K.
Published: July 2002

Recent laboratory and field observations suggest that the effects of nonlinearity and dispersion may be significant for the evolution of Kelvin waves in rotating channels. Here, it is shown that a pair of Kelvin wave modes may interact with a third Poincaré mode to form a resonant triad. The evolution of the triad is governed by the well-known three-wave interaction equations. The implications of this instability for naturally occurring Kelvin waves are discussed.
Parametric instability of supersonic shear layers induced by periodic Mach waves
Authors: Hu Fang Q. , Tam Christopher K. W.
Published: July 2002

It is suggested that parametric instability can be induced in a confined supersonic shear layer by the use of a periodic Mach wave system generated by a wavy wall. The existence of such an instability solution is demonstrated computationally by solving the Floquet system of equations. The solution is constructed by means of a Fourier–Chebyshev expansion. Numerical convergence is assured by using a very large number of Fourier and Chebyshev basis functions. The computed growth rate of the induced flow instability is found to vary linearly with the amplitude of the mach waves when the amplitude is not excessively large. This ensures that the instability is, indeed, tied to the presence of the Mach waves. It is proposed that enhanced mixing of supersonic shear layers may be achieved by the use of such a periodic Mach wave system through the inducement of parametric instabilities in the flow.
Vortex properties of two-dimensional turbulence
Authors: Dritschel David G.
Published: July 2002

Novel physical-space vortex properties of nearly inviscid, unforced two-dimensional (2-D) turbulence are presented. They are obtained from the analysis of a large ensemble of calculations all beginning with a random distribution of vortex patches of equal vorticity magnitude on a spherical surface. The numerical method (MACS) is a combination of contour dynamics/surgery (CD/CS) and a moment expansion for calculating separated vortex interactions. This method calculates approximately 100 times faster than CD/CS thereby permitting the formation of a large database for obtaining meaningful statistics. The numerical method can resolve a much wider range of spatial scales than conventional (pseudospectral) methods, and it is found that the statistical vortex properties produced differ in significant respects from those obtained previously. This conclusion is drawn from not just one set of calculations, but three at different spatial resolutions. While algebraic decay of basic flow statistics (e.g., enstrophy, vortex population) is observed at late times, the decay exponents are smaller than previously obtained and furthermore do not come in the ratios suggested by the recently proposed ‘‘universal scaling theory.’’ In addition, the vortex number density distribution is not found to be self-similar but steepens continuously and appreciably with decreasing vortex size. This forces a reevaluation of the nature of 2-D turbulence in the inviscid limit. A proper description of this limit needs (more) quantitative information concerning the most probable vortex interactions. Such interactions will not be between just two vortices, as is commonly supposed.
Global external magnetohydrodynamic instabilities in straight noncircular Z pinches
Authors: Spies Günther O.
Published: July 2002

The straight EXTRAP experiment [Phys. Scr. 16, 147 (1977); Nucl. Instrum. Methods 207, 223 (1983)] is modeled as a magnetohydrostatic equilibrium with cylindrical symmetry and a plane magnetic field. The plasma is surrounded by a vacuum that extends to infinity, and in which four axial rod currents are placed symmetrically. The plasma current density is either parallel or antiparallel to the rod currents, thus having one sign throughout. In the stability analysis, the configuration is assumed to have a finite axial length (the boundary conditions appropriate to a rigid perfect conductor are imposed at the two ends), and the rods are assumed to be permeable to the magnetic field. According to ideal magnetohydrodynamics, such an equilibrium is globally unstable to flute modes and/or slip modes unless the rod currents vanish (circular Z pinch). This is due to the increase away from the center of the octupole field of the rods.
Inverse mode conversion of ion Bernstein waves in tokamak plasmas
Authors: Romero H. , Morales G. J.
Published: July 2002

The inverse linear mode conversion between an electrostatic ion Bernstein wave and an electromagnetic fast Alfvén wave in tokamak plasmas is investigated using a self-adjoint system of equations of fourth order that includes cyclotron and Landau damping processes. Over a broad range of cases investigated, the reciprocity of the mode conversion coefficients between the ion Bernstein and fast waves is observed to hold, within numerical accuracy, even in the presence of strong cyclotron absorption. It is also found that strong bulk ion heating occurs at twice the cyclotron frequency for direct launching of an ion Bernstein wave into a plasma that contains no ionic species that are resonant at the fundamental cyclotron frequency.
Evolution equation for infinitesimal rotational discontinuities
Authors: Sonnerup B. U. Ö. , Qian S. , Wang D.-J.
Published: July 2002

A two-fluid model that allows for finite deviations from charge neutrality is used to describe the temporal evolution of rotational discontinuities (nonlinear Alfvén waves) of the type described by Wang and Sonnerup [Phys. Fluids 27, 1640 (1984)]. These elementary-pulse equilibria have the electrostatic structure of an ion-acoustic soliton but they also have an associated small net rotation of the magnetic field. A reductive perturbation expansion is carried out and is shown to lead to an evolution equation consisting of the Korteweg–de Vries equation with an added term that describes the self-consistent magnetic effects in the wave. This term can be cast in the form of a convolution integral, the convolution kernel being a simple exponential function. Five integrals of the equation are derived. The equation is integrated numerically to show that the elementary-pulse solutions by Wang and Sonnerup are metastable in the sense that they persist in an unchanged form for long simulation times. However, when the initial pulse shape is different, no evolution toward the elementary-pulse shape takes place. Instead, the wave pulse either disintegrates or transforms itself into a true equilibrium intermediate-mode solitary wave. The propagation speed of this solitary wave exceeds the Alfvén speed slightly and the magnetic field undergoes no net change across it. The properties of these new solitary waves are analyzed and discussed.
Magnetic electron drift vortex mode instability in a cylindrical plasma
Authors: Stenflo L. , Yu M. Y. , Shukla P. K.
Published: July 2002

An equation describing the propagation and instability behavior of magnetic electron drift vortex modes in a cylindrically symmetric rotating plasma is derived without using the local approximation. The effects of equilibrium density, velocity, and temperature, as well as magnetic field gradients, are included. An approximate analytical solution for modes near the center of the plasma is obtained.
Universal interchange instability in partially ionized gases
Authors: Huba J. D.
Published: July 2002

A magnetized, inhomogeneous, partially ionized gas is theoretically shown to be unstable to an interchange instability. The source of free energy for the instability is the cross-field current. The instability is caused by neutral drag dynamics, and is therefore critically dependent upon charged particle–neutral collisions ναn. The growth rate is largest in the strongly coupled regime, i.e., ω≪νin, νni, and is given by γ≂(εme/mi)1/2(1+ε)−1kyVd, where ky is the wave number, Vd=(cT/eB)[∂ ln(ni0)/∂x] is the diamagnetic drift velocity, T=Te+Ti, and ε=mnnn/mini [m is the mass and n the density of the ions (i) and neutrals (n)]. The growth rate is a maximum when ε=1, which corresponds to νin=νni.