Showing papers on "Symmetry (physics) published in 1995"
Book•
01 Jan 1995
TL;DR: Inverse scattering and Darboux Transformations have been used in the theory of solitons as discussed by the authors for nonlinear nonlinear wave propagation, where the soliton theory and differential geometry have been combined.
Abstract: 1 Soliton Theory and Modern Physics.- 2 Inverse Scattering Methods.- 3 Backlund Transformations and Darboux Transformations.- 4 Classical Integrable Systems.- 5 Symmetry.- 6 Kac-Moody Algebras and Integrable Systems.- 7 Soliton and Differential Geometry.- 8 Numerical Study of Nonlinear Waves.- 9 Solitons in the Theory of Gravitational Waves.- References.
246 citations
TL;DR: In this paper, the authors show that half-integer flux quantization in superconducting rings with three grain-boundary Josephson junctions, which formed the basis of an earlier, less conclusive symmetry test, can be used to place firm constraints on the pairing symmetry.
Abstract: RECENT discussions of the mechanism of high-temperature superconductivity have focused on the symmetry of the superconducting order parameter (the wavefunction of the superconducting state) as a means of constraining the nature of the interaction that forms the Cooper pairs1,2. There have been many attempts to measure the symmetry of this parameter in the high-temperature superconductor YBa2Cu3O7 - δ (refs 3–10), but they have not yielded consistent results. Here we show that half-integer flux quantization in superconducting rings with three grain-boundary Josephson junctions, which formed the basis of an earlier, less conclusive symmetry test3, can be used to place firm constraints on the pairing symmetry. For the case of YBa2Cu3O7 - δ, we find that the sign of the order parameter is clearly direction dependent (consistent with a dx2-y2 symmetry) and that the contribution from any out-of-phase isotropic component is less than about 3%.
238 citations
TL;DR: In a generic supersymmetric extension of the Standard Model, whether unified or not, a simple and well motivated U(2) symmetry, acting on the lightest two generations, completely solves the flavour changing problem and leads to a predictive texture for the Yukawa couplings as discussed by the authors.
Abstract: In a generic supersymmetric extension of the Standard Model, whether unified or not, a simple and well motivated U(2) symmetry, acting on the lightest two generations, completely solves the flavour changing problem and necessarily leads to a predictive texture for the Yukawa couplings.
205 citations
TL;DR: In this article, the free wave equations of motion, subsidiary conditions and corresponding gauge transformations for such fields were derived and used to derive the lowest eigenvalues of the energy operator for the representations under consideration.
192 citations
TL;DR: In this article, it is shown that infinitely many vacua are accessible to memory printing in a way that in sequential information recording the storage of a new information does not destroy the previously stored ones, thus allowing a huge memory capacity.
Abstract: The quantum model of the brain proposed by Ricciardi and Umezawa is extended to dissipative dynamics in order to study the problem of memory capacity. It is shown that infinitely many vacua are accessible to memory printing in a way that in sequential information recording the storage of a new information does not destroy the previously stored ones, thus allowing a huge memory capacity. The mechanism of information printing is shown to induce breakdown of time-reversal symmetry. Thermal properties of the memory states, as well as their relation with squeezed coherent states, are finally discussed.
188 citations
TL;DR: In this paper, a magnetoelectric effect is predicted: the supercurrent in a metal of polar symmetry must be accompanied by the spin polarization of the carriers, and the relevance to some known pyro-and antipyroelectric superconductors including a high-temperature system as well as the possibility of an experimental verification are briefly discussed.
Abstract: The question of how the lack of spatial reflection symmetry can affect properties of a superconductor is investigated. A novel magnetoelectric effect is predicted: The supercurrent in a metal of polar symmetry must be accompanied by the spin polarization of the carriers. The relevance to some known pyro- and antipyroelectric superconductors including a high-temperature system as well as the possibility of an experimental verification are briefly discussed.
182 citations
TL;DR: In this article, the authors study the cosmology of the Supersymmetric Standard Model augmented by a gauge singlet to solve the μ-problem and describe the evolution of the domain walls which are created during electroweak symmetry breaking due to the discrete Z 3 symmetry in this model.
176 citations
TL;DR: In this paper, it was shown that the two-dimensional theory is equivalent to planar symmetry in general relativity, and that the 2D theory admits black holes and free dilatons, and has a structure similar to 2D string theories.
Abstract: The Einstein--Hilbert action with a cosmological term is used to derive an action in 1+1 spacetime dimensions. It is shown that the two-dimensional theory is equivalent to planar symmetry in general relativity. The two-dimensional theory admits black holes and free dilatons, and has a structure similar to two-dimensional string theories. Since by construction these solutions also solve Einstein's equations, such a theory can bring two-dimensional results into the four-dimensional world. In particular the two-dimensional black hole is a black membrane in general relativity.
167 citations
TL;DR: In this paper, the authors investigated boundary integrable models that possess N = 2 supersymmetry on the half-space and found that supersymmetric models largely determine boundary action in terms of the bulk, and in particular, the boundary bosonic potential is |W|2, where W is the bulk superpotential.
160 citations
TL;DR: In this article, a generalization of the notion of invariance of a given partial differential equation with respect to Lie-Backlund vector field is proposed, which enables us to construct principally new Ans\"atze reducing evolution-type equations to several ordinary differential equations.
Abstract: We suggest a generalization of the notion of invariance of a given partial differential equation with respect to Lie-B\"acklund vector field. Such generalization proves to be effective and enables us to construct principally new Ans\"atze reducing evolution-type equations to several ordinary differential equations. In the framework of the said generalization we obtain principally new reductions of a number of nonlinear heat conductivity equations $u_t=u_{xx}+F(u,u_x)$ with poor Lie symmetry and obtain their exact solutions. It is shown that these solutions can not be constructed by means of the symmetry reduction procedure.
158 citations
TL;DR: The scale invariance of the O (3) sigma model can be broken by gauging a U (1) subgroup of the symmetry and including a Maxwell term for the gauge field in the Lagrangian as mentioned in this paper.
TL;DR: In this article, the authors study the cosmology of the Supersymmetric Standard Model augmented by a gauge singlet and describe the evolution of the domain walls which are created during electroweak symmetry breaking due to the discrete $Z_{3}$ symmetry in this model.
Abstract: We study the cosmology of the Supersymmetric Standard Model augmented by a gauge singlet to solve the $\mu$-problem and describe the evolution of the domain walls which are created during electroweak symmetry breaking due to the discrete $Z_{3}$ symmetry in this model. The usual assumption, that non-renormalizable terms induced by gravity (which explicitly break this symmetry) may cause the walls to collapse on a cosmologically safe timescale, is reconsidered. Such terms are constrained by considerations of primordial nucleosynthesis, and also by the fact that by not respecting the $Z_{3}$ symmetry they induce divergences which destabilise the hierarchy and reintroduce the $\mu$--problem. We find that, even when the K\"ahler potential is `non-minimal' (i.e. when the hidden sector couples directly to the visible) the model is either ruled out cosmologically or suffers from a naturalness problem.
TL;DR: In this paper, it was shown that chiral symmetry restoration in quenched finite temperature QCD depends crucially on the phase of the Polyakov loop, which is a general consequence of the coupling of the chiral order parameter to the polyakov loop.
Abstract: We demonstrate that chiral symmetry restoration in quenched finite temperature QCD depends crucially on the $Z_3$ phase of the Polyakov loop ${\cal P}$. This dependence is a general consequence of the coupling of the chiral order parameter to the Polyakov loop. We construct a model for chiral symmetry breaking and restoration which includes the effect of a nontrivial Polyakov loop by calculating the effective potential for the chiral condensate of a Nambu-Jona-Lasinio model in a uniform temperature dependent $A_0$ gauge field background. Above the deconfinement temperature there are three possible phases corresponding to the $Z_3$ symmetric phases of the Polyakov loop in the pure gauge theory. In the phase in which ${\rm tr_c}({\cal P})$ is real and positive the first order deconfining transition induces chiral symmetry restoration in agreement with simulation results. In the two phases where $Re[{\rm tr_c}({\cal P})] < 0$ the sign of the leading finite temperature correction to the effective potential is reversed from the normal phase, and chiral symmetry is not restored at the deconfinement transition; this agrees with the recent simulation studies of Chandrasekharan and Christ. In the case of $SU(N)$ a rich set of possibilites emerges. The generality of the mechanism makes it likely to occur in full QCD as well; this will increase the lifetimes of metastable $Z_3$ phases.
TL;DR: In this paper, the vacuum structure of supersymmetric QCD with fundamental quarks was determined in terms of families of hyperelliptic Riemann surfaces of genus equal to the rank of the gauge group.
Abstract: We determine the vacuum structure of N=2 supersymmetric QCD with fundamental quarks for gauge groups SO(n) and Sp(2n), extending prior results for SU(n). The solutions are all given in terms of families of hyperelliptic Riemann surfaces of genus equal to the rank of the gauge group. In the scale invariant cases, the solutions all have exact S-dualities which act on the couplings by subgroups of PSL(2,Z) and on the masses by outer automorphisms of the flavor symmetry. They are shown to reproduce the complete pattern of symmetry breaking on the Coulomb branch and predict the correct weak--coupling monodromies. Simple breakings with squark vevs provide further consistency checks involving strong--coupling physics.
TL;DR: A stabilizing control law is derived that achieves arbitrary reorientation of the spacecraft under the assumption that the initial spin rate about the symmetry axis is zero.
TL;DR: In this article, the authors define constrained Hamiltonian systems with symmetry and prove a reduction theorem for the case of a convex heavy body rolling without slipping on a horizontal plane, and prove that the time evolution of the system is governed by a well defined differential equation on the manifold.
Abstract: A mechanical system with perfect constraints can be described, under some mild assumptions, as a constrained Hamiltonian system(M, Ω, H, D, W): (M, Ω) (thephase space) is a symplectic manifold,H (theHamiltonian) a smooth function onM, D (theconstraint submanifold) a submanifold ofM, andW (theprojection bundle) a vector sub-bundle ofT
D
M, the reduced tangent bundle alongD. We prove that when these data satisfy some suitable conditions, the time evolution of the system is governed by a well defined differential equation onD. We define constrained Hamiltonian systems with symmetry, and prove a reduction theorem. Application of that theorem is illustrated on the example of a convex heavy body rolling without slipping on a horizontal plane. Two other simple examples show that constrained mechanical systems with symmetry may have an attractive (or repulsive) set of relative equilibria.
TL;DR: I acknowledge support from NSF Grant No.
Abstract: It is shown that the theorem asserting separability of the center of mass motion for a system of interacting particles in a harmonic external potential is satisfied in the time dependent density functional theory, provided that the exchange-correlation potential satisfies a simple symmetry under transformation to an accelerated frame of reference. Examples of approximations for the exchange-correlation potential which satisfy or violate this symmetry are given.
TL;DR: In this paper, a superstring-inspired supersymmetric model with a low energy extra U(1) symmetry was studied and a rather wide parameter region was found to have the favorable feature for the radiative symmetry breaking at weak scale.
Abstract: Radiative symmetry breaking is studied in a superstring-inspired supersymmetric model which is extended with a low energy extra U(1) symmetry. In this model the μ problem is radiatively solved in an automatic way. The right-handed neutrino can be heavy and the seesaw mechanism will produce the small neutrino mass which makes the MSW solution applicable to the solar neutrino problem. We search a parameter region which has the favorable feature for the radiative symmetry breaking at the weak scale. A rather wide parameter region is found to be allowed. Although there are certain dependences on the soft supersymmetry breaking parameters in the estimation of masses of various fields, the upper bound of the extra Z boson mass is estimated to be mZ2≤2000 GeV for a top mass range 150 GeV≤mt≤190 GeV within a suitable parameter region (m0<1 TeV and m1/2<200 GeV). Some phenomenological features of the extra Z boson are also presented.
TL;DR: Within a specific texture of the quark mass matrix, the notion of a maximal violation of the CP symmetry can be defined as mentioned in this paper, which vanishes as the mass of the u-quark approaches zero.
TL;DR: The results suggest that the pseudospin symmetry in heavy nuclei yields to the chiral symmetry of massless hadrons in the high energy region.
Abstract: A many-particle operator that affects a transformation to the pseudospin basis in heavy nuclei is identified. Both mean-field and many-particle estimates demonstrate that in the helicity-transformed representation the nucleons move in a finite-depth nonlocal potential with a reduced spin-orbit strength. Because of the close relation between the helicity and chirality operations, the results suggest that the pseudospin symmetry in heavy nuclei yields to the chiral symmetry of massless hadrons in the high energy region.
TL;DR: This work finds the "critical" spacetime separating the two phases of the spherisymmetric real scalar field system by demanding discrete scale-invariance, analyticity, and an additional reflection-type symmetry.
Abstract: By fine-tuning generic Cauchy data, critical phenomena have recently been discovered in the black hole/no black hole "phase transition" of various gravitating systems. For the spherisymmetric real scalar field system, we find the "critical" spacetime separating the two phases by demanding discrete scale-invariance, analyticity, and an additional reflection-type symmetry. The resulting nonlinear hyperbolic boundary value problem, with the rescaling factor Delta as the eigenvalue, is solved numerically by relaxation. We find Delta = 3.4439 +/- 0.0004.
TL;DR: An accurate and detailed semiempirical intermolecular potential energy surface for (HCl)2 has been determined by a direct nonlinear least-squares fit to 33 microwave, far-infrared and near-inf infrared spectroscopic quantities using the analytical potential model of Bunker et al.
Abstract: An accurate and detailed semiempirical intermolecular potential energy surface for (HCl)2 has been determined by a direct nonlinear least‐squares fit to 33 microwave, far‐infrared and near‐infrared spectroscopic quantities using the analytical potential model of Bunker et al. [J. Mol. Spectrosc. 146, 200 (1991)] and a rigorous four‐dimensional dynamical method (described in the accompanying paper). The global minimum (De=−692 cm−1) is located near the hydrogen‐bonded L‐shaped geometry (R=3.746 A, θ1=9°, θ2=89.8°, and φ=180°). The marked influence of anisotropic repulsive forces is evidenced in the radial dependence of the donor–acceptor interchange tunneling pathway. The minimum energy pathway in this low barrier (48 cm−1) process involves a contraction of 0.1 A in the center of mass distance (R) at the C2h symmetry barrier position. The new surface is much more accurate than either the ab initio formulation of Bunker et al. or a previous semiempirical surface [J. Chem. Phys. 78, 6841 (1983)].
TL;DR: In this paper, the authors study space-times which evolve out of Cauchy data invariant under the action of a two-dimensional commutative Lie group and prove that asymptotic flatness, energy conditions, and cylindrical symmetry exclude the existence of compact trapped surfaces.
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31 Mar 1995
TL;DR: In this article, the authors studied the spectral properties of Bogomolny monopoles and showed that the space of such monopoles is a geodesic submanifold of the monopole moduli space.
Abstract: We discuss $SU(2)$ Bogomolny monopoles of arbitrary charge $k$ invariant under various symmetry groups The analysis is largely in terms of the spectral curves, the rational maps, and the Nahm equations associated with monopoles We consider monopoles invariant under inversion in a plane, monopoles with cyclic symmetry, and monopoles having the symmetry of a regular solid We introduce the notion of a strongly centred monopole and show that the space of such monopoles is a geodesic submanifold of the monopole moduli space By solving Nahm's equations we prove the existence of a tetrahedrally symmetric monopole of charge $3$ and an octahedrally symmetric monopole of charge $4$, and determine their spectral curves Using the geodesic approximation to analyse the scattering of monopoles with cyclic symmetry, we discover a novel type of non-planar $k$-monopole scattering process
TL;DR: In this article, the influence of weak non-magnetic disorder on the singleparticle density of states ϱ(ω) of two-dimensional electron systems with a conical spectrum is studied.
TL;DR: In this article, the symmetry properties of finite-difference equations on uniform lattices are determined and it is found that they retain the same Lie symmetry algebras as their continuum limits.
Abstract: Discretizations of the Helmholtz, heat, and wave equations on uniform lattices are considered in various space–time dimensions. The symmetry properties of these finite‐difference equations are determined and it is found that they retain the same Lie symmetry algebras as their continuum limits. Solutions with definite transformation properties are obtained; identities and formulas for these functions are then derived using the symmetry algebra.
TL;DR: In this article, the authors analyzed the structure of models with unbroken and spontaneously broken U (1) a × U(1) b gauge symmetry and showed that the quantum corrections to the 2 N gauge charges, with N = number of fermions + number of scalars, can be absorbed in the redefinition of three independent gauge couplings ( g a, g b, and g ab ).
TL;DR: In this article, a method for parametrizing heavy meson semileptonic form factors using dispersion relations was presented, and from it a two-parameter description of the B -> B elastic form factor was obtained.
Abstract: We present a method for parametrizing heavy meson semileptonic form factors using dispersion relations, and from it produce a two-parameter description of the B -> B elastic form factor. We use heavy quark symmetry to relate this function to B->D* l
u form factors, and extract |V_{cb}|=0.037^{+0.003}_{-0.002} from experimental data with a least squares fit. Our method eliminates model-dependent uncertainties inherent in choosing a parametrization for the extrapolation of the differential decay rate to threshold. The method also allows a description of B -> D l nu form factors accurate to 1% in terms of two parameters.