Coarse grained approach for volume conserving models

Volume conserving surface (VCS) models without deposition and evaporation, as well as ideal molecular-beam epitaxy models, are prototypes to study the symmetries of conserved dynamics. In this work we study two similar VCS models with conserved noise, which differ from each other by the axial symmetry of their dynamic hopping rules. We use a coarse-grained approach to analyze the models and show how to determine the coefficients of their corresponding continuous stochastic differential equation (SDE) within the same universality class. The employed method makes use of small translations in a test space which contains the stationary probability density function (SPDF). In case of the symmetric model we calculate all the coarse-grained coefficients of the related conserved Kardar–Parisi–Zhang (KPZ) equation. With respect to the symmetric model, the asymmetric model adds new terms which have to be analyzed, first of all the diffusion term, whose coarse-grained coefficient can be determined by the same method. In contrast to other methods, the used formalism allows to calculate all coefficients of the SDE theoretically and within limits numerically. Above all, the used approach connects the coefficients of the SDE with the SPDF and hence gives them a precise physical meaning.     

Temperature dependence of volume and surface symmetry energy coefficients of nuclei

The thermal evolution of the energies and free energies of a set of spherical and near-spherical nuclei spanning the whole periodic table are calculated in the subtracted finite-temperature Thomas–Fermi framework with the zero-range Skyrme-type KDE0 and the finite-range modified Seyler–Blanchard interaction. The calculated energies are subjected to a global fit in the spirit of the liquid-drop model. The extracted parameters in this model reflect the temperature dependence of the volume symmetry and surface symmetry coefficients of finite nuclei, in addition to that of the volume and surface energy coefficients. The temperature dependence of the surface symmetry energy is found to be very substantial whereas that of the volume symmetry energy turns out to be comparatively mild.     

Study ofpf-shell nuclei with a symmetry conserving generator coordinate method

Bands based on the 0⁺ ground state and the first excited 0⁺ pairing vibrational state of⁴⁸Ti,⁵²Cr and⁵⁶Fe are studied with the generator coordinate method. The generating wave functions for each value of the angular momentumJ are angular momentum and particle number projected selfconsistent Hartree-Fock-Bogoliubov states where the constrained amount of pairing correlations serves as the generator coordinate. The interaction is given by reaction matrix elements derived from the Hamada-Johnston force. The basis includes the four lowest oscillator shells. The excitation energies of the pairing vibrational states can be reproduced fairly well by the present choice of the generating wave functions, whereas the ground band is not much improved compared to projected Hartree-Bogoliubov calculations. We find that the strength of the pairing correlations in the 0⁺ and 2⁺ states of the ground state and the pairing vibrational bands can be related to data of two-particle transfer reactions. The angular momentum dependence of the pairing correlations and of the moments of inertia are studied. The results show that for a strongly paired ground state the ground state band and the pairing vibrational band intersect. This may produce in the yrast band the anomaly of the moment of inertia known from rare earth nuclei.     

Tendency towards sphericity symmetry of pebbles: The rate change of volume with surface

The primary effect of rocks and stones tending to erode towards sphericity symmetry can be identified with the rate change of volume with surface. Marble pebbles of various shapes and sizes are recorded and modeled mathematically as ellipsoids. The rate change of volume with surface dV/dA is computed for flat-shaped pebbles where the thickness dimension is assumed to be unity. Invoked is the hypothesis that the change of shape and size of pebbles can be characterized by a master curve derived from dA/dL, the 2D version of dV/dA. The sphericity symmetry is assumed to be concerned with the preference of roundness to slenderness regardless of the surface roughness, smoothness and the mineralogical composition. The erosiveness and abrasiveness of the surface and time effects can interact with sphericity, which is an issue beyond the scope of this work.     

Solution of a symmetry conserving chiral soliton model for nucleon and delta

The linear chiral soliton model is solved for nucleon and delta by constructing Fock states in the coherent pair approximation with correct spin and isospin properties. The quark configurations are those arising from theSU(2)×SU(2) coupling of three quarks in 1s-orbits. The overall Fock state is formed by the vector coupling of the quark configurations with the pion coherent state and thus avoids the use of the hedgehog ansatz. The sigma field is treated in the mean field approximation. Equations of motion for the quark, sigma and pion fields are solved in the static approximation. Soliton solutions are found with properties that are in reasonable agreement with those observed for the nucleon and delta including the axial vector coupling constant. With only components having zero and one unpaired pion in the coherent pair approximation the nucleon mass is found to be larger than that using the projected hedgehog approach.     

点电荷、线电荷、面电荷模型的电荷体分布函数

利用δ函数,导出了点电荷、线电荷和面电荷模型在直角坐标、球坐标和柱坐标下的电荷体分布函数表达式,对处理一些具体的物理问题时十分有用。     

Molecular symmetry governs surface diffusion

In chemistry and physics symmetry principles are all important, for example, leading to the selection rules governing optical transitions. We have investigated the influence of the molecular symmetry on the surface potential landscape of molecules in the limit of weak molecule-substrate binding. For this purpose, the induced lateral motion of Cu(II)-tetraazaphthalocyanine molecules, for which four symmetry distinct isomers exist, on NaCl(100) was studied by scanning tunneling microscopy. This nonthermal diffusion induced by inelastic excitations is found to be qualitatively different for all four symmetry distinct isomers, demonstrating that symmetry governs the surface potential landscape.     

Dual models and spontaneous symmetry breaking

The question of spontaneous symmetry breaking in dual models is investigated. In the context of a particular model with a conserved “charge”, two different approaches to the problem, spurion emission and the effective potential methods, are developed. A method is described for the calculation of the effective potential, and it is applied to determine the first few terms of the potential.     

Dual models with a colour symmetry

It is shown that all dual models derived maively from a recently discovered class of infinite graded Lie algebras with O(N) symmmetry posses ghosts if N > 2 with the possible exception of the quaternion case.     

Gauge symmetry breaking in matrix models

We argue that some features of the standard model, in particular the fermion assignment and symmetry breaking, can be obtained in matrix model which describes noncommutative gauge theory as well as gravity in an emergent way. The mechanism is based on the presence of some extra (matrix) dimensions. These extra dimensions are different from the usual ones which give to a noncommutative geometry of the Grönewold-Moyal type, and are reminiscent of the Connes-Lott model, although the action is very different.     

Twisted custodial symmetry in two-Higgs-doublet models

In the standard model for electroweak interactions, the Higgs sector is known to display a custodial symmetry protecting the mass relation m(W(+/-))(2) = m(W(3))(2) from large corrections. When considering extensions of the scalar sector, this symmetry has to be introduced by hand in order to pass current electroweak precision tests in a natural way. In this Letter, we implement a generalized custodial symmetry in the two-Higgs-doublet model. Assuming the invariance of the potential under CP transformations, we prove the existence of a new custodial scenario characterized by m(H(+/-))(2) = m(H(0))(2) instead of m(H(+/-))(2) = m(A(0))(2). Consequently, the pseudoscalar A(0) may be much lighter than the charged H(+/-), giving rise to interesting phenomenology.     

Radiative symmetry breaking in supersymmetric models

We propose a scheme where the three relevant physics scales related to the supersymmetry, electroweak, and baryon minus lepton (B−L) breakings are linked together and occur at the TeV scale. The phenomenological implications in the Higgs and leptonic sectors are discussed.     

Yangian symmetry in deformed WZNW models on squashed spheres

We introduce a deformation of the Wess-Zumino-Novikov-Witten model with three-dimensional squashed sphere target space. We show how with an appropriate choice of Wess-Zumino and boundary terms it is possible to construct an infinite family of conserved charges realizing an SU(2) Yangian. Finally we discuss the running of the squashing parameter under renormalization group flow.     

The space group symmetry of surface structure

The symmetry of a crystal with an ideal surface is investigated. It is shown that the two-dimensional space group symmetry of the crystal should be used rather than the pure translational symmetry.     

Supersymmetric preon models with gauged colour-flavour symmetry

We have conducted a search for globally supersymmetric preon models with gauged colour-flavour symmetries. Theories with both two- and three-preon composites, and colour-flavour groups from E₆ down to the standard model, are examined under the following conditions: asymptotically-free metacolour, anomaly-free gauged symmetries, and Pauli principle obeyed. It is found that there are no models with three or more supersymmetric families. If supersymmetry is broken, one model with four families emerges. The purely fermionic preon theories can also be considered as the light sector of a chiral supersymmetric theory, with supersymmetry breaking at the preon level.     

Neutrino mass sum-rules in flavor symmetry models

Four different neutrino mass sum-rules have been analyzed: these frequently arise in flavor symmetry models based on the groups A₄$A_4$, S₄$S_4$ or T^′$T^{\prime }$, which are often constructed to generate tri-bimaximal mixing. In general, neutrino mass can be probed in three different ways, using beta decay, neutrino-less double beta decay and cosmology. The general relations between the corresponding three neutrino mass observables are well known. The sum-rules lead to relations between the observables that are different from the general case and therefore only certain regions in parameter space are allowed. Plots of the neutrino mass observables are given for the sum-rules, and analytical expressions for the observables are provided. The case of deviations from the exact sum-rules is also discussed, which can introduce new features. The sum-rules could be used to distinguish some of the many models in the literature, which all lead to the same neutrino oscillation results.