scispace - formally typeset
Search or ask a question

Showing papers on "Symmetry (physics) published in 1985"


Journal ArticleDOI
TL;DR: In this article, additional symmetries in two-dimensional conformal field theory generated by spin s = 1/2, 1,...,3 currents were investigated and the generators of the symmetry form associative algebras with quadratic determining relations.
Abstract: This paper investigates additional symmetries in two-dimensional conformal field theory generated by spin s = 1/2, 1,...,3 currents. For spins s = 5/2 and s = 3, the generators of the symmetry form associative algebras with quadratic determining relations. ''Minimal models'' of conforma field theory with such additional symmetries are considered. The space of local fields occurring in a conformal field theory with additional symmetry corresponds to a certain (in general, reducible) representation of the corresponding algebra of the symmetry.

910 citations


Journal ArticleDOI
TL;DR: In this article, the authors study the general signatures of a strongly interacting W, Z system and conclude that these two possibilities can be unambiguously distinguished by a hadron collider facility capable of observing the enhanced production of WW, WZ and ZZ pairs that will occur if W's and Z's have strong interactions.

669 citations


Journal ArticleDOI
TL;DR: In this paper, the symmetry and stability of icosahedral incommensurate structures and generalized two-dimensional Penrose pentagonal structures are studied, with or without improper translations.
Abstract: The symmetry and stability of icosahedral incommensurate structures and generalized two-dimensional Penrose pentagonal structures are studied. The crystallographic properties of Penrose lattices are described by five-dimensional (5D) super space groups, and the icosahedral structures are described by 6D space groups, with or without improper translations. The density in real space is given as the density along a three-dimensional plane in this 6D space. The fivefold symmetry of the diffraction spectrum of Mn-Al alloys, which is inconsistent with three-dimensional translational invariance, reflects a fivefold rotation axis of the 6D space group. The six continuous degrees of freedom associated with the 6D space represent the usual three orthogonal rigid displacements of the crystal, plus three phase shifts associated with internal rearrangements, leading to three acoustic-phonon modes and three phason modes. There are two independent elastic constants, which is fewer than in any regular crystal, representing one-dimensional and five-dimensional irreducible strains, respectively. If the phase degrees of freedom are included, there are five generalized elastic constants. The stability of icosahedral structures and ``lyotropic'' Penrose structures can be understood from a phenomenological Landau theory. The ideal icosahedral crystal has perfect positional order, which is stable with respect to thermal fluctuations at low temperatures. The melting transition is first order.

266 citations


Journal Article
TL;DR: In this article, a two-dimensional exactly solvable model of a conformal quantum field theory is developed which is self-dual and has Z/sub N/ symmetry.
Abstract: A two-dimensional exactly solvable model of a conformal quantum field theory is developed which is self-dual and has Z/sub N/ symmetry. The operator algebra, the correlation functions, and the anomalous dimensions of all fields are calculated for this model, which describes self-dual critical points in Z/sub N/-symmetric statistical systems.

216 citations


Journal ArticleDOI
TL;DR: In this paper, a generalization of Hopf Bifurcation Theorem to differential equations with symmetry was proposed, analogous to a static bifurcation theorem of Cicogna.
Abstract: Using group theoretic techniques, we obtain a generalization of the Hopf Bifurcation Theorem to differential equations with symmetry, analogous to a static bifurcation theorem of Cicogna. We discuss the stability of the bifurcating branches, and show how group theory can often simplify stability calculations. The general theory is illustrated by three detailed examples: O(2) acting on R2, O(n) on Rn, and O(3) in any irreducible representation on spherical harmonics.

214 citations


Journal ArticleDOI
TL;DR: In this article, an extensive region of nuclei near A = 130 resembling the O(6) symmetry of the IBA is presented, and other similarities between these two regions are found, in particular, a common relation of the energy scales of the O (6) and O(5) groups.

201 citations


Journal ArticleDOI
TL;DR: In this paper, the complete N = 8 d = 5 supergravity action and supersymmetry transformation laws (without four and three-fermion terms) were obtained from the ungauged model by reinterpreting part of the field strenghts of the abelian vector fields as real self-dual second-rank antisymmetric tensors.

199 citations


Journal ArticleDOI
TL;DR: In this article, a new analysis of two-dimensional many-electron systems subject to periodic boundary conditions in a magnetic field leads to a fully twodimensional structure of the quantum numbers at rational Landau-level filling.
Abstract: In contrast to previous treatments, a new analysis of two-dimensional many-electron systems subject to periodic boundary conditions in a magnetic field leads to a fully two-dimensional structure of the quantum numbers at rational Landau-level filling. The structure of the new symmetry analysis has an intrinsically many-particle character. Full agreement between numerical studies of quantized-Hall-effect systems in periodic and spherical geometries is achieved, and the problem of ground-state degeneracy is clarified.

182 citations


Journal ArticleDOI
TL;DR: In this paper, exact analytical solutions of the static Einstein-Maxwell equations for perfect and anisotropic fluids were found under the assumption of spherical symmetry and the existence of a one-parameter group of conformal motions.
Abstract: Some exact analytical solutions of the static Einstein–Maxwell equations for perfect and anisotropic fluids were found under the assumption of spherical symmetry and the existence of a one‐parameter group of conformal motions. All solutions are matched to the Reissner‘xnNordstrom metric and possess positive energy density larger than the stresses, everywhere within the sphere.

179 citations


Journal ArticleDOI
TL;DR: A metastable phase with the point group symmetry m35 was found in rapidly quenched (Ti 1−xVx)2Ni alloys with × = 00-0-3 by electron diffraction and high-resolution electron microscopy as discussed by the authors.
Abstract: A metastable phase with the point group symmetry m35 but no ordinary translation symmetry has been found in rapidly quenched (Ti 1−xVx)2Ni alloys with × = 00-0-3 by electron diffraction and high-resolution electron microscopy.

176 citations


Journal ArticleDOI
TL;DR: In this article, a new mechanism of quark and lepton mass generation via their mixing with hypothetical superheavy fermions is discussed for the model with the SU(5) ⊗ SU(3) H symmetry.

Journal ArticleDOI
TL;DR: Group theory is used to classify p-wave superconducting states in a cubic crystal with spin-orbit coupling and all possible stable states are obtained based on the most general form of the Ginzburg-Landau free energy.
Abstract: Group theory is used to classify p-wave superconducting states in a cubic crystal with spin-orbit coupling. All possible stable states are obtained based on the most general form of the Ginzburg-Landau free energy. Within the weak-coupling theory all stable states have real order parameters. These real states are even under time-reversal symmetry. However, in general, states with complex order parameters are also possible. In these complex states time-reversal symmetry is broken. This broken symmetry may show up through the existence of a Josephson current between a complex p-wave state and a usual s-wave superconductor. The form of the pairing in a magnetic field is also discussed.

Journal ArticleDOI
TL;DR: In this paper, a class of three-dimensional periodic flows of an incompressible viscous fluid with high symmetry in space is proposed to be used for numerical simulation of large Reynolds number flows in order to increase the effective resolution.
Abstract: A class of three-dimensional periodic flows of an incompressible viscous fluid with high symmetry in space is proposed to be used for numerical simulation of large Reynolds number flows in order to increase the effective resolution. Information for a single component of the velocity in a domain of 1/64 in volume of a periodicity box is sufficient to describe the whole velocity field. Necessary memory therefore may be reduced to 1/192 of that required for a general non-symmetric periodic flow.


Journal ArticleDOI
TL;DR: In this article, a general symmetry criterion is derived for establishing the existence of surface states in solids, which applies to surface states terminating at symmetry planes (or symmetry centers in one dimension).
Abstract: A general symmetry criterion is derived for establishing the existence of surface states in solids. Two kinds of surfaces in solids are distinguished: those coinciding with symmetry planes (or symmetry centers in one dimension) and those in general positions. The symmetry criterion applies to surface states in solids terminating at symmetry planes (or symmetry centers in one dimension). A detailed discussion is given for one-dimensional crystals. The application of the symmetry criterion is demonstrated on the Kronig-Penney, nearly-free-electron, tight-binding, and Mathieu potentials. In particular, it is shown that the Maue and Shockley existence conditions for surface states follow from the general symmetry criterion.

Journal ArticleDOI
TL;DR: In this article, exact analytical solutions of the Einstein equations for perfect fluids were found under the assumption of spherical symmetry and the existence of a one-parameter group of conformal motions.
Abstract: Some exact analytical solutions of the Einstein equations for perfect fluids were found under the assumption of spherical symmetry and the existence of a one‐parameter group of conformal motions. The first solution exhibited represents a nonstatic homogeneous spherically symmetric distribution of matter which is singular at t=0. Two other solutions represent contracting and expanding fluids, respectively, whose evolution tends asymptotically to a static sphere with a surface gravitational potential equal to (1)/(3) . These two solutions possess vanishing pressure surfaces which are not the boundary of matter except in the static limit. Finally an oscillating distribution of matter is presented.

Journal ArticleDOI
TL;DR: A REDUCE package for determining the group of Lie symmetries of an arbitrary system of partial differential equations is described in this paper, which can be used both interactively and in a batch mode.
Abstract: A REDUCE package for determining the group of Lie symmetries of an arbitrary system of partial differential equations is described. It may be used both interactively and in a batch mode. In many cases the system finds the full group completely automatically. In some other cases there are a few linear differential equations of the determining system left the solution of which cannot be found automatically at present. If it is provided by the user, the infinitesimal generators of the symmetry group are returned.

Journal ArticleDOI
TL;DR: In this paper, a simple interpretation of the decomposition of the densities of states in the classical mechanical limit according to the regular representation of the permutation group and under certain circumstances, the molecular symmetry group is presented.
Abstract: A simple interpretation of the decomposition of the densities of states in the classical mechanical limit according to the regular representation of the permutation group and—under certain circumstances—the molecular symmetry group is presented. The relationship between recent results on densities of states of a given point group symmetry species and previous results based upon the molecular symmetry group is established. Some restrictions are discussed as well as the definition and application of symmetry numbers for the densities of states and partition functions of nonrigid and rigid molecules and transition states.

Journal ArticleDOI
TL;DR: In this paper, the SO(5)-gauged maximal d = 7 supergravity was derived from the recently obtained SO(4, 1) and SO(3, 2) gaugings.

Journal ArticleDOI
TL;DR: In this article, two mechanisms for the detection of E1 transitions in nuclei were discussed, and they imply that isospin should be viewed as a local rather than a global symmetry.

Journal ArticleDOI
M. I. Wanas1
TL;DR: In this paper, three solutions with spherical symmetry are obtained for the field equations of the generalized field theory established recently by Mikhail and Wanas, which correspond to a field in a matter-free space.
Abstract: Three solutions with spherical symmetry are obtained for the field equations of the generalized field theory established recently by Mikhail and Wanas. The solutions found are in agreement with classical known results. The solution representing a generalized field, outside a spherical symmetric charged body, is found to have an extra term compared with the Reissner-Nordstrom metric. The space used for application is of type FIGI, so the solutions obtained correspond to a field in a matter-free space. A brief comparison between the solutions obtained and those given by other field theories is given. Two methods have been used to get physical results: the first is the type analysis, and the second is the comparison with classical known results by writing down the metric of the associated Riemannian space.

Journal ArticleDOI
TL;DR: In this article, the resistive MHD equations are linearized around an equilibrium with cylindrical symmetry and solved numerically as a complex eigenvalue problem, which allows one to solve for very small resistivity γ≈10 -10.

Journal ArticleDOI
TL;DR: In this article, it was shown that homogeneous and inhomogeneous components of a wave field have quite different symmetry properties under phase conjugation, and the results are illustrated by a discussion of the behavior of plane waves, both homogenous and evanescent ones.
Abstract: Several theorems are known concerning symmetry relations between monochromatic wave fields that propagate either into the same half-space (z > 0) or into complementary half-spaces (z > 0 and z < 0) and that are complex conjugates of each other in some cross-sectional plane z = constant. The theorems derived up to now apply only to wave fields that do not contain inhomogeneous (evanescent) components. In the present paper two of the main theorems are generalized to a wider class of fields. It is found that homogeneous and inhomogeneous components of a wave field have quite different symmetry properties under phase conjugation. The results are illustrated by a discussion of the behavior of plane waves, both homogeneous and evanescent ones, which undergo phase conjugation followed by transmission or by reflection.

Journal ArticleDOI
TL;DR: In this article, the Schrodinger equation for a spin-0 particle in the field of a dyon is obtained by dimensional reduction of the four-dimensional harmonic oscillator; the reduction is effected by imposing an equivariance condition on the wave functions of the latter system.

Journal ArticleDOI
TL;DR: In this article, the complete solution for the quantum-mechanical problem of a particle in an equilateral triangle is derived by use of projection operators, eigenfunctions belonging explicitly to each of the irreducible representations of the symmetry group C3V are constructed.
Abstract: The complete solution for the quantum‐mechanical problem of a particle in an equilateral triangle is derived. By use of projection operators, eigenfunctions belonging explicitly to each of the irreducible representations of the symmetry group C3V are constructed. The most natural definition of the quantum numbers p and q includes not only integers but also nonintegers of the class (1)/(3) and (2)/(3) modulo 1. Some relevant features relating to symmetry and degeneracy are also discussed.

Journal ArticleDOI
TL;DR: In this article, a series of response tensors relating the electric field at a nucleus in a molecule to external fields and field gradients is defined, each new tensor is a derivative of a molecular multipole moment or polarizability with respect to motion of that nucleus.

Book
01 Jan 1985
TL;DR: In this paper, an introduction to unitary symmetry and secret symmetry breakdown is given, as well as a review for non-specialists of symmetry breakdown and gauge fields, and the uses of instantous symmetry.
Abstract: Preface Acknowledgements 1. An introduction to unitary symmetry 2. Soft pions 3. Dilatations 4. Renormalization and symmetry: a review for non-specialists 5. Secret symmetry: an introduction to spontaneous symmetry breakdown and gauge fields 6. Classical lumps and their quantum descendants 7. The uses of instantous 8. 1/N Appendices Notes and references.

Journal ArticleDOI
TL;DR: In this article, the authors make a careful analysis of the constraints on supergravity parameters from the requirement of SU(2)×U(1) symmetry breaking, and obtain fully analytic solutions to the relevant renormalization group equations, they are able to explore the whole range of parameters.

Journal ArticleDOI
TL;DR: In this paper, the authors describe a discretization method using an "orthogonal triangular double grid" to solve for fields with azimuthal variation in cavities with dielectric and/or permeable insertions.
Abstract: The design of rf accelerating structures nowadays is largely based on mesh-codes that solve for fields and eigenfrequencies in arbitrarily shaped cavities The most developed codes deal with structures of cylindrical symmetry However, no program is available that can solve for fields with azimuthal variation in cavities with dielectric and/or permeable insertions Here we describe a discretization method Using an "orthogonal triangular double grid" The special mesh and the FIT-discretization /1,2/ enable the treatment of cavities with arbitrary material insertions and combines the features of SUPERFISH /3/ (triangular mesh, rotationally symmetric fields) and URMEL /4/ (rectangular mesh but field with or without azimuthal variation)

Journal ArticleDOI
TL;DR: In this article, a new method of estimating crystal field parameters is proposed using crystal field invariants in conjunction with the superposition model, and the importance of using a fixed reference frame throughout a series of fitting based on approximate symmetries is stressed.
Abstract: Relationships between crystal field invariants and superposition model parameters are established. Various strategies are examined for determining and assessing the reliability of crystal field parameters for lanthanide ions in low‐symmetry sites. In particular, a new method of estimating crystal field parameters is proposed using crystal field invariants in conjunction with the superposition model. The importance of using a fixed reference frame throughout a series of fitting based on approximate symmetries is stressed and this leads us to identify a new simplified parametrization for lanthanide ions in LaF3 which is not related to an approximate symmetry.