Showing papers on "Symmetry (physics) published in 1988"
TL;DR: In this paper, the cosmological constant problem in the light of dilatation symmetry and its possible anomaly is discussed, and it is shown that the energy-momentum tensor in the vacuum is purely anomalous and that deviations from the standard hot big bang cosmology are possible.
2,385 citations
TL;DR: In this article, the use of effective chiral Lagrangians with vector mesons in the description of low-energy hadron physics is discussed, with particular emphasis on the gauged Wess-Zumino action and vector meson Dominance.
542 citations
TL;DR: An auxiliary-boson mean-field theory consistent with the SU(2) symmetry of the Heisenberg model is formulated and it is found that T/sub c/ vanishes at large and small filling factors.
Abstract: We have formulated an auxiliary-boson mean-field theory consistent with the SU(2) symmetry of the Heisenberg model. At half filling, we find an infinite number of solutions related by the symmetry. Away from half filling the kinetic energy, acting as a symmetry-breaking field, selects a superconducting state of d-wave symmetry. The mean-field theory describes bosons and fermions with finite kinetic energy close to half filling. We derive self-consistent equations for the superconducting transition temperature ${T}_{c}$. We find that ${T}_{c}$ vanishes at large and small filling factors.
411 citations
TL;DR: The relationship between the maximum neutron- star mass and observable parameters of the equation of state is explored and it is concluded that the compression modulus cannot, by itself, be severely limited by observed neutron-star masses.
Abstract: The relationship between the maximum neutron-star mass and observable parameters of the equation of state is explored. In particular, the roles of the nuclear incompressibility and the symmetry energy are considered. It is concluded that, for realistic symmetry energies, the compression modulus cannot, by itself, be severely limited by observed neutron-star masses. Several directions for further study are suggested.
292 citations
TL;DR: In this paper, it was shown that the behavior of the system can be analyzed in terms of an effective lagrangian, whose coupling constants are independent of the temperature, but, in general, depend on the volume.
244 citations
TL;DR: It is found that the next-higher-order terms beyond the ladder approximation amount to only a 1%--20% correction, depending on the fermion representation, indicating that the ladder expansion may provide a much better description of chiral-symmetry breaking than previously thought.
Abstract: This paper examines the validity of the ladder approximation in gauge theories such as technicolor theories in which the coupling is a slowly running function of momentum and is large enough to trigger spontaneous chiral-symmetry breaking. We find that the next-higher-order terms beyond the ladder approximation amount to only a 1%--20% correction, depending on the fermion representation. This indicates that the ladder expansion may provide a much better description of chiral-symmetry breaking than previously thought.
127 citations
TL;DR: In this paper, it was shown that all supercritical solitary wave solutions to the equations for water waves are symmetric and monotone on either side of the crest of the wave.
Abstract: It is shown that all supercritical solitary wave solutions to the equations for water waves are symmetric, and monotone on either side of the crest. The proof is based on the Alexandrov method of moving planes. Further a priori estimates, and asymptotic decay properties of solutions are derived
126 citations
TL;DR: In this article, it is shown that the exploitation of symmetry via group invariance also yields an efficient computational approach to global bifurcation problems, which leads to a drastic reduction in numerical effort in the determination of several global solution branches, and enables the accurate computation of numerous singular points.
Abstract: Bifurcation of solution branches in static or steady problems of nonlinear mechanics is often associated with the underlying symmetry of the physical system. The use of group-theoretic methods in local bifurcation theory for problems with symmetry is well known. In this paper it is shown that the exploitation of symmetry via group invariance also yields an efficient computational approach to global bifurcation problems. These techniques are illustrated in the analysis of a lattice-dome structure with hexagonal symmetry. The methodology leads to a drastic reduction in numerical effort in the determination of several global solution branches, and enables the accurate computation of numerous singular points.
120 citations
TL;DR: In this paper, a general Laurent expansion for monogenic functions in symmetric domains of R m + 1 was proved, depending on the kind of symmetry involved and applied to axial exponential functions, generalized power functions and generalized Hermite polynomials.
111 citations
01 Jan 1988
TL;DR: The size of relativistic effects, scaling behavior, sensitivity to the nucleon-nucleon interactions, and effects of the uncertainties in measured nucleon form factors are investigated.
Abstract: Measurements of the deuteron form factors over a wide range of momentum transfer can provide important clues to the role of subnucleon degrees of freedom in nuclear dynamics. For a meaningful calculation of the form factors it is essential that the current density operators and the deuteron wave function transform under Lorentz transformations in a mutually consistent manner. Standard nucleon-nucleon interactions can be used to construct unitary representations of the Poincare group on the two-nucleon Hilbert space. Deuteron wave functions represent eigenstates of the four-momentum operator. Existing parameterizations of measured single-nucleon form factors are used to construct a conserved covariant electromagnetic current operator. The light-front symmetry of the representation allows a clean separation of the effects of one- and two-body currents for arbitrary momentum transfers. Comparison with data indicates that for Q/sup 2/ < GeV/sup 2/ the elastic cross sections are not dominated by two-body currents.
TL;DR: In this paper, a new symmetry for the ground state of the skyrmion crystal was proposed and the minimum energy per baryon of a crystal having this symmetry was only 3.8% above the lower bound and 4% below the lowest energy obtained so far.
TL;DR: It is shown that H3 surface functions at constant hyperspherical radius can be calculated very accurately and efficiently using SADVRs based on either D3h or C2v symmetry.
Abstract: A general approach for the construction of symmetry‐adapted discrete variable representations (SADVR) is described. The method is shown to give DVRs of Gaussian quadrature accuracy. The SADVR is explicitly constructed for the nuclear motion of three atom systems with D3h symmetry (e.g., H3 or H+3 ) in hyperspherical coordinates. It is shown that H3 surface functions at constant hyperspherical radius can be calculated very accurately and efficiently using SADVRs based on either D3h or C2v symmetry.
TL;DR: In this article, a systematic collection of spatial domains for reciprocal space integrations is derived for all possible crystal symmetries. But the analysis is restricted to integrations where the function in the integrand satisfies inversion symmetry in k space.
Abstract: A systematic collection of spatial domains for reciprocal space integrations is derived for all possible crystal symmetries. This set can be used as a simpler alternative to the conventional Brillouin zones. The analysis is restricted to integrations where the function in the integrand satisfies inversion symmetry in k space. In this case only 24 different spatial domains have to be defined in order to allow for k space integrations in the 230 different crystal symmetries. A graphic representation of the asymmetric unit for each of the 24 integration domains is given. Special positions and the associated weighting factors required for numerical integrations in theoretical solid-state approaches are tabulated.
TL;DR: In this article, the authors present exemples which montrent que des espaces homogenes homeomorphes ne sont pas necessary necessairement diffeomorphehes.
Abstract: On donne des exemples qui montrent que des espaces homogenes homeomorphes ne sont pas necessairement diffeomorphes
TL;DR: In this paper, a toy model where CP invariance enforces neutral flavor conservation in a nontrivial way is discussed, and a complete analysis of the possible mixing matrices for any number of generations is performed for the usual case of real Yukawa couplings.
Abstract: CP invariance of SU(2)L×U(1) gauge theories is formulated in the most general way. Certain useful standard forms for CP transformations are presented. After a review of horizontal symmetries inducing neutral flavor conservation, we discuss a toy model where CP invariance enforces neutral flavor conservation in a nontrivial way. It is shown that spontaneous CP violation in its general form and neutral flavor conservation lead to a real mixing matrix for three generations. For more than three generations, the mixing matrix may violate CP. A complete analysis of the possible mixing matrices for any number of generations is performed for the usual case of real Yukawa couplings. If the mixing matrix violates CP, some of its elements must be equal in absolute magnitude. For four generations, all possible structures compatible with experiment are specified.
TL;DR: Icosahedral symmetry analysis is used to determine the eigenvalues and eigenvectors of a classical spring mass model of Buckyball in this article, and several choices for spring constants are discussed and a comparison with spring mass systems of reduced symmetry is made.
TL;DR: In this article, the retrieval phase of spin-glass-like neural networks is studied, and the effects of symmetry and symmetry on the short-time dynamics of this model are studied analytically.
Abstract: The authors study the retrieval phase of spin-glass-like neural networks. Considering that the dynamics should depend only on gauge-invariant quantities, they propose that two such parameters, characterising the symmetry of the neural net's connections and the stabilities of the patterns, are responsible for most of the dynamical effects. This is supported by a numerical study of the shape of the basins of attraction for a one-pattern neural network model. The effects of stability and symmetry on the short-time dynamics of this model are studied analytically, and the full dynamics for vanishing symmetry is shown to be exactly solvable.
TL;DR: The algebraic properties of rotational bands generated using collective models based on dynamical groups are shown to be remarkably resilient to strong symmetry mixing by the spin-orbit interaction.
TL;DR: In this article, the structure of the generators of the asymptotic Poincare symmetry in the general R+T2+R2 theory of gravity is obtained by using the Hamiltonian formalism.
Abstract: The structure of the generators of the asymptotic Poincare symmetry in the general R+T2+R2 theory of gravity is obtained by using the Hamiltonian formalism. It is shown that a correct treatment of the generators leads to the appearance of certain surface terms, which determine the values of the gravitational energy, momentum and angular momentum.
TL;DR: In this article, the authors proposed the vectorial tomography (V2T) method to retrieve the 3D distributions of seismic velocities and of anisotropy characterized as a vector by an amplitude and the two angles of the symmetry axis.
Abstract: SUMMARY By inverting the azimuthal dependence of Rayleigh and Love dispersions (including the azimuthally averaged term) it is possible to separate the effect of anisotropy from other effects creating lateral heterogeneities (mainly thermal). The different steps of the tomographic method are described. In the first step, we retrieve the geographical distributions of the different azimuthal dispersion terms of Rayleigh and Love waves. For a complete slightly anisotropic medium, these distributions are dependent upon 13 combinations of elastic moduli. This number of parameters is too large and in order to interpret these distributions as simply as possible in terms of elastic properties of the medium, some realistic assumptions about the material can be made. The simplest way to explain the azimuthal distributions is to assume that the medium possesses a symmetry axis but contrarily to previous investigations, it is assumed that the orientation of this axis is not necessarily vertical. In that case, one shows how to retrieve simultaneously the 3-dimensional distributions of seismic velocities and of anisotropy characterized as a vector by an amplitude and the two angles of the symmetry axis. This complete process has been named ‘vectorial tomography’ and can provide valuable information about convection and also mineralogical composition.
TL;DR: In this paper, the authors constructed a gauge field theory based on GA(4, R ) space-time symmetry, containing spinorial and tensorial (infinite component) matter manifields.
TL;DR: In this article, it was shown that the most general central extension compatible with the Jacobi identity is characterized by the space of harmonic one-forms on the membrane, whose dimension is twice the genus of the surface.
TL;DR: Using the Skyrme model of strong interactions, the authors found periodic static solutions of the Euler-Lagrange equations having a rectangular symmetry similar to that found in studies of neutron crystals.
TL;DR: In this article, the boundary-collocation truncated-series solution technique for planar symmetric Stokes flow problems has been extensively modified to treat the non-symmetric multibody problem.
Abstract: This paper contains an ‘exact’ solution for the hydrodynamic interaction of a three-dimensional finite cluster at arbitrarily sized spherical particles at low Reynolds number. The theory developed is the most general solution to the problem of an assemblage of spheres in a three-dimensional unbounded media. The boundary-collocation truncated-series solution technique of Ganatos, Pfeffer & Weinbaum (1978) for treating planar symmetric Stokes flow problems has been extensively modified to treat the non-symmetric multibody problem. The orthogonality properties of the eigenfunctions in the azimuthal direction are used to satisfy the no-slip boundary conditions exactly on entire rings on the surface of each particle rather than just at discrete points.Detailed comparisons with the exact bipolar solutions for two spheres show the present theory to be accurate to five significant figures in predicting the translational and angular velocity components of the particles at all orientations for interparticle gap widths as close as 0.1 particle diameter. Convergence of the results to the exact solution is rapid and systematic even for unequal-sized spheres (a1/a2 = 2). Solutions are presented for several interesting and intriguing configurations involving three or more spherical particles settling freely under gravity in an unbounded fluid or in the presence of other rigidly held particles. Advantage of symmetry about the origin is taken for symmetric configurations to reduce the collocation matrix size by a factor of 64. Solutions for the force and torque on three-dimensional clusters of up to 64 particles have been obtained, demonstrating the multiparticle interaction effects that arise which would not be present if only pair interactions of the particles were considered. The method has the advantage of yielding a rather simple expression for the fluid velocity field which is of significance in the treatment of convective heat and mass transport problems in multiparticle systems.
TL;DR: In this article, an introduction to CP violating phenomena is given and the standard model and its most popular low energy extensions are reviewed in this context, including the minimal supersymmetric extension, left-right symmetries, and more than one Higgs doublet.
Abstract: An introduction to CP violating phenomena is given and the standard model and its most popular low energy extensions are reviewed in this context. The discussion comprises the minimal supersymmetric extension of the standard model, left-right symmetry, the standard model with more than one Higgs doublet and gauged horizontal symmetries.
TL;DR: In this article, the N = 8 supersymmetric singleton field theory is formulated on the boundary of the four-dimensional anti-de Sitter spacetime (AdS 4 ).
TL;DR: In this paper, a list of 547 group-subgroup pairs of space groups which are not incompatible with balance surfaces for symmetry reasons is given, and the symmetry conditions that have to be fulfilled by all balance surfaces are tabulated in addition.
Abstract: A list of those 547 group-subgroup pairs of space groups is given which are not incompatible with balance surfaces for symmetry reasons. The symmetry conditions that have to be fulfilled by all balance surfaces are tabulated in addition. Two kinds of non-cubic minimal balance surfaces have been derived completely: (1) 7 families of minimal balance surfaces which may be generated by skew circuits of 2-fold axes that are disk-like spanned, (2) 7 families of minimal balance surfaces which may be generated by pairs of parallel flat circuits of 2-fold axes that are catenoid-like spanned.
TL;DR: In this paper, the effect of couette flow on a range of ensemble averages was determined by establishing the symmetry of the strain rate tensor in terms of the irreducible representations of the Rh (3) rotation reflection group in the XYZ frame.
Abstract: We describe group theory statistical mechanics, GTSM, which enables us to predict new non-vanishing time correlation functions in fluids at steady state subjected to planar couette flow. These are by symmetry trivially zero at equilibrium. An ensemble average is treated using the rules of group theory in the laboratory XYZ frame and in the molecule-fixed xyz frame of the point group character tables. In this paper we determine the effect of couette flow on a range of ensemble averages by establishing the symmetry of the strain rate tensor in terms of the irreducible representations of the Rh (3) rotation reflection group in the XYZ frame. This symmetry, D (0) g + D (1) g + D (2) g , is the same as the pressure tensor, P and consists of an antisymmetric vorticity term, D (1) g and a symmetric strain rate component of symmetry D (0) g + D (2) g . This allows non-zero ensemble averages of the same symmetry in the XYZ frame. Depending on the number of off-diagonal elements in the strain rate tensor, up to six...
TL;DR: For perfect fluids with the equation of state p=( gamma -1) mu ( gamma =constant) the static cylindrically symmetric solution which is regular at the symmetry axis is given in a closed form.
Abstract: For perfect fluids with the equation of state p=( gamma -1) mu ( gamma =constant) the static cylindrically symmetric solution which is regular at the symmetry axis is given in a closed form. In addition to gamma the solution contains a real parameter which determines the central pressure. The limit gamma =2 and the special case of plane symmetry are considered.