Showing papers on "Explicit symmetry breaking published in 1987"
TL;DR: The MISSYM program as discussed by the authors is part of the NRCVAX system of programs, which allows the user to report either a different space group or the existence of pseudo-symmetry whenever extra structural symmetry elements are disclosed by the program.
Abstract: The space-group symmetry implied in the atomic coordinates of a structure can be reconstructed by deriving the metric symmetry elements of the lattice from the cell data, and finding the location and the glide for corresponding space-group symmetry elements with the same orientation using the list of atomic coordinates. The MISSYM computer program designed along these principles treated correctly the known examples of overlooked symmetry or quasi-symmetry that were submitted to it. As no computer program operating on refined atomic coordinates can prove the presence of extra symmetry in the crystal, the user should scrutinize the experimental evidence and report either a different space group or the existence of pseudo-symmetry whenever extra structural symmetry elements are disclosed by the program. The MISSYM program is part of the NRCVAX system of programs.
354 citations
TL;DR: A Skyrmion may be regarded as a topologically non-trivial map from one Riemannian manifold to another, minimizing a particular energy functional as mentioned in this paper.
Abstract: A Skyrmion may be regarded as a topologically non-trivial map from one Riemannian manifold to another, minimizing a particular energy functional. We discuss the geometrical interpretation of this energy functional and give examples of Skyrmions on various manifolds. We show how the existence of conformal transformations can cause a Skyrmion on a 3-sphere to become unstable, and how this may be related to chiral symmetry breaking.
192 citations
Book•
31 Jan 1987
TL;DR: The role and value of symmetry principles and Einstein's contribution to their recognition are discussed in this article. But the authors focus on the application of the symmetry principles to the atomic shell model of the Nucleus.
Abstract: Why We Believe in the Einstein Theory.- The Role and Value of the Symmetry Principles and Einstein's Contribution to Their Recognition.- Statistical Concepts in Einstein's Physics.- What Are the True Building Blocks of Matter.- Classification of Wigner Operators by a New Type of Weight Space Diagram.- De Sitter Fibers and SO(3,2) Spectrum Generating Group for Hadrons.- The Wigner-Racah Algebra for Finite and Compact Continuous Groups.- Applications of Coherent States in Thermodynamics and Dynamics.- The Application of Imbedding Theory to the Atomic Shell Model.- Group Theory in Atomic and Molecular Physics.- New Approach to Matrix Elements and Clebsch-Gordan Coefficients for Compact and Non-Compact Groups.- Group Theory and the Interaction of Composite Nucleon Systems.- Time Reversal in Dissipative Systems.- Life Groups, Quantum Mechanics, Many-Body Theory and Organic Chemistry.- Symmetry and Variable Separation for the Helmholtz, Wave and Hamilton-Jacobi Equations.- Review of the Group Theory behind the Interacting Boson Model of the Nucleus.- Remarks on the Algebraic Structure of Spontaneous Symmetry Breaking in Unified Gauge Theories.- Symmetry Breaking and Far-From-Equilibrium Order.- Finite Subgroups of the Lorentz Group and Their Generating Functions.- On Dynamical Symmetries in Relativistic Field Theories.- On the Generalisation of the Gell-Mann-Nishijima Relation.- Relativistic Dynamical Groups in Quantum Theory and Some Possible Applications.- Generalized Coherent States.- Spontaneous Symmetry Breaking in Bifurcation Problems.- Time, Energy, Relativity, and Cosmology.- Projection Operators for Semisimple Compact Lie Groups and Their Applications.- Orders in Nature: From Quantum to Classical.- Systematic Methods for Determining the Continuous Transformation Groups Admitted by Differential Equations.- Symmetry Breaking in Embryology and in Neurobiology.- On Global Properties of Quantum Systems.- Invited Speakers and Invited Participants.
94 citations
TL;DR: In this paper, it was shown that an early period of inflation which gives the desired flatness, dilution of unwanted species, and density fluctuations also eliminates the problem associated with intermediate scale breaking.
81 citations
Book•
01 Jan 1987
TL;DR: A discussion of developments in the field of bifurcation theory, with emphasis on symmetry breaking and its interrelationship with singularity theory is given in this article, where universal solutions, symmetry breaking, and unfolding of singularities are discussed in detail.
Abstract: A discussion of developments in the field of bifurcation theory, with emphasis on symmetry breaking and its interrelationship with singularity theory. The notions of universal solutions, symmetry breaking, and unfolding of singularities are discussed in detail. The book not only reviews recent mathematical developments but also provides a stimulus for further research in the field.
81 citations
66 citations
TL;DR: In this paper, the symmetry classification of possible singlet and also triplet states in the case of the 2-dim square lattice, and 3-dim tetragonal and orthorhombic lattices is examined.
Abstract: The symmetry classification of possible singlet and also triplet states in the case of the 2-dim square lattice, and 3-dim tetragonal and orthorhombic lattices is examined. If particle-hole symmetry is present then an additional symmetry classification is possible. However in the lower symmetry crystal structures that actually occur, no distinction on symmetry grounds can be drawn between usuals-wave, extendeds-wave and some of thed-wave states.
58 citations
Journal Article•
56 citations
TL;DR: It should be possible to design quick and nondestructive methods for the identification of certain small objects, when suitable partial information about the objects to be identified is already available, according to the conclusions of this work.
Abstract: The symmetry theorems on the complete forward and backward scattering Mueller matrices for light scattering from a single dielectric scatterer (as opposed to an ensemble of scatterers) are systematically and thoroughly analyzed. Symmetry operations considered include discrete rotations about the incident direction and mirror planes not coinciding with the scattering plane. For forward scattering we find sixteen different symmetry shapes (not including the totally asymmetric one), which may be classified into five symmetry classes, with identical reductions in the forward scattering matrices for all symmetry shapes that fall into the same symmetry class. For backward scattering we find only four different symmetry shapes, which may be classified into only two symmetry classes. The forward scattering symmetry theorems also lead to a symmetry theorem on the total extinction cross section. Based on the conclusions of this work it should be possible to design quick and nondestructive methods for the identification of certain small objects, when suitable partial information about the objects to be identified is already available. A promising practical example is given.
54 citations
TL;DR: In this article, the EPR spin Hamiltonian parameters for all crystallographic point symmetries possible for a paramagnetic center are presented, with particular attention paid to ambiguities in parameter sets and equivalent sets for each symmetry for various conventional choices of coordinate frames.
50 citations
TL;DR: By applying bifurcation theory to a truncated Dyson-Schwinger equation for the quark propagator in massless QCD, the authors showed that dynamical symmetry breaking occurs at a certain critical value of the coupling constant.
Abstract: By applying bifurcation theory to a truncated Dyson-Schwinger equation for the quark propagator in massless QCD, we show that dynamical symmetry breaking occurs at a certain critical value of the coupling constant. Essential ingredients are (a) an effective dynamical mass for the gluon, and (b) a running coupling constant.
TL;DR: In this paper, it has been shown that light dilaton is unlikely in the case of a slowly varying running coupling and chiral symmetry breaking, and the effect of a physical high energy cutoff as motivated in a technicolor context.
TL;DR: In this paper, the authors evaluated the contribution of charge symmetry breaking (CSB) potentials to energy differences in mirror nuclei and to the scattering length differences app−ann and ann−anp from class III and class IV type CSB potentials.
TL;DR: In this article, the consequences of the invariance of the superpotential under the complexification of the internal symmetry group on the determination of the possible patterns of symmetry and supersymmetry breaking are established in a globally supersymmetric theory.
Abstract: The consequences of the invariance of the superpotential under the complexificationG
c of the internal symmetry group on the determination of the possible patterns of symmetry and supersymmetry breaking are established in a globally supersymmetric theory. In particular, in the case of global internal symmetry we show that a vacuum associaated to a pointz, whereG
z
c
≠G
z
c
is always degenerate with a vacuum associated to a pointz′, whereG
z′
c
=G
z′
c
; all the other degeneracies of the minimum of the potential on an orbit ofG
c are also determined and shown to be completely removed when the internal symmetry is gauged. The zeroes of theD-term of a supersymmetric gauge theory are characterized as the points of the closed orbits ofG
c which are at minimum distance from the origin; at these pointsG
z
c
=G
z
c
. It is rigorously proved that the minimum of the potential is zero if the gradient of the superpotential vanishes somewhere. It is also shown that theD-term necessarily vanishes at the minimum of the potential if the direction of spontaneous supersymmetry breaking is invariant byG.
TL;DR: In this article, the authors present a model with continuous or discrete abelian generation group G, which predicts all orders of magnitude for fermion masses ad mixings correctly as a function of only one small parameter φSM ≈ 110.
TL;DR: In this article, conditions for symmetric coherence transfer under composite processes consisting of pulses and precession periods are formulated and the symmetry of two-dimensional N.M.R. spectra with respect to reflection about the diagonal serves as a concrete example.
Abstract: The symmetry of coherence transfer between pairs of transitions in quantum mechanical systems is investigated. Conditions for symmetric transfer under composite processes consisting of pulses and precession periods are formulated. The symmetry of two-dimensional (2D) N.M.R. spectra with respect to reflection about the diagonal serves as a concrete example. The current experimental 2D N.M.R. techniques are analysed in view of symmetry and examples of experiments are discussed that lead to asymmetric coherence transfer and asymmetric 2D spectra.
TL;DR: In this paper, it was shown that superstring models with simple discrete symmetries may have an approximate Peccei-Quinn symmetry in the low-energy effective lagrangian.
Book•
01 Jan 1987
TL;DR: In this article, the authors discuss mirror symmetry, a symmetries, time reversal, vacuum as a physical medium, spontaneous symmetry breaking, particles, and quarks, and describe symmetry breaking.
Abstract: Discusses mirror symmetry, a symmetries, time reversal, vacuum as a physical medium, spontaneous symmetry breaking, particles, and quarks.
TL;DR: For large d, the diluted antiferromagnet can be mapped with Gaussian randomness and the phase diagram has a de Almeida-Thouless line, marking the onset of the glassy phase.
Abstract: The conventional mean-field theory of random-field systems is, for large but finite dimensionalities d, found to be in error. For larger applied fields, a separate glassy phase appears in the phase diagram of the bond-diluted antiferromagnet. For large d, the diluted antiferromagnet can be mapped on the antiferromagnet with Gaussian randomness and the phase diagram of this model is shown to have a de Almeida--Thouless line, marking the onset of the glassy phase by replica symmetry breaking. In the limit d\ensuremath{\rightarrow}\ensuremath{\infty} we recover conventional mean-field theory.
TL;DR: In this paper, the terms responsible for g/u coupling are removed from the kinetic energy operator at the expense of introducing additional terms in the potential, and a new hamiltonian having the correct dissociation limits is obtained and the corresponding Schrodinger equation is largely separable.
Abstract: Symmetry breaking corrections for HD+ are estimated by performing a unitary transformation on the hamiltonian. The terms responsible for g/u coupling are removed from the kinetic energy operator at the expense of introducing additional terms in the potential. The effective electrostatic potential may be interpreted in terms of effective nuclear charges. A new hamiltonian having the correct dissociation limits is obtained and the corresponding Schrodinger equation is largely separable. The resulting corrections to the energy compare well with previous work, particularly at large bond lengths, and the electric dipole moment and electron densities at the nuclei show the correct behaviour near dissociation.
TL;DR: In this paper, a hierarchy of scales in the coset space can change the spontaneous symmetry breaking of the four-dimensional gauge theory, where Higgs fields and the corresponding potential appear naturally.
TL;DR: In this article, the effective potential for spontaneous breaking of chiral symmetry was calculated for finite temperatures and baryon densities from a Nambu-Jona-Lasinio type of Lagrangian with explicit flavour symmetry breaking by bare quark masses.
Abstract: The effective potential for spontaneous breaking of chiral symmetry is calculated for finite temperatures and baryon densities from a Nambu-Jona-Lasinio type of Lagrangian with explicit flavour symmetry breaking by bare quark masses.
TL;DR: In this paper, an approximation method based on dimer coverings for the ground state of the antiferromagnetic Heisenberg lattice is described, and the working of the method is demonstrated by some small-system calculations.
Abstract: An approximation method, based on dimer coverings, for the ground state of the antiferromagnetic Heisenberg lattice is described. The working of the method is demonstrated by some small-system calculations. The method introduces a possible mechanism for symmetry breaking for two- and higher-dimensional systems.
TL;DR: In this article, the magnetic dipole matrix elements were derived for γ → γ and γ→ g.s.b. transitions using a slightly broken neutron-proton (F -spin) symmetry.
TL;DR: In this paper, the effects arising from the n-p mass difference and ω-ϱ mixing were evaluated from a momentum-space one-bosom-exchange potential.
TL;DR: In this article, the problem of baryogenesis in superstring unification with intermediate gauge symmetry breaking was studied and it was shown that it is possible to obtain an appreciable baryon number asymmetry if certain phenomenological conditions are satisfied for the model parameters.
TL;DR: In this paper, it was shown that the existence of a non-trivial three-cocycle on the local gauge group is not a sign of a failure of the associative law.
TL;DR: In this article, a finite temperature and density effect of Wilson loop elements on non-simply connected space is investigated in the model suggested by Hosotani, and it is shown that the value of an order parameter does not shift as the temperature grows.
Abstract: A finite temperature and density effect of Wilson loop elements on non-simply connected space is investigated in the model suggested by Hosotani. Using one-loop calculations it is shown that the value of an “order parameter” does not shift as the temperature grows. We find that finite density effect is of much importance for restoration of symmetry.
TL;DR: Vacuum polarization and spontaneous symmetry breaking in a two-dimensional massless fermion field theory with quartic interactions (the Gross-Neveu model) are studied in a cylindrical space-time topology.
Abstract: Vacuum polarization and spontaneous symmetry breaking in a two-dimensional massless fermion field theory with quartic interactions (the Gross-Neveu model) are studied in a cylindrical (${R}^{1}$\ifmmode\times\else\texttimes\fi{}${S}^{1}$) space-time topology. In the case of untwisted fermion fields the symmetry-breaking behavior is similar to the model in Minkowski space-time except that the location of the effective potential minima depends upon the size of the space. In the case of a twisted fermion field there exists a critical size of the space such that the symmetry breaking occurs only for space larger than the critical one.
TL;DR: In this article, a generalisation of Parisi's replica symmetry breaking scheme to spin glasses is proposed, where the model is solved exactly in the large p limit and a freezing transition occurs.
Abstract: The authors propose a generalisation of Parisi's replica symmetry breaking scheme (1979) to spin glasses (or optimisation problems) described by a set of order parameters Q(r)alpha 1. . . alpha r, or equivalently by a global order parameter G( sigma alpha ), rather than by Q(r)alpha 1 alpha 2 alone. They study the particular case of Derrida's p-spin model (1981) in the very dilute limit. The model is solved exactly in the large p limit and a freezing transition occurs. Using replicas and a single step of their replica symmetry breaking ansatz they recover the exact result. They discuss the implications for the global order parameter G( sigma alpha ) when more than one step in the replica symmetry breaking process is taken.