Nonconical theory of flow past slender wing bodies with leading-edge separation

Nonconical theory of flow past slender wing bodies with leading edge separatio

Mass Shift and Width Broadening of J/psi in hot gluonic plasma from QCD Sum Rules

We investigate possible mass shift and width broadening of J/psi in hot gluonic matter using QCD sum rule. Input values of gluon condensates at finite temperature are extracted from lattice QCD data for the energy density and pressure. Although stability of the moment ratio is achieved only up to T/Tc ~ 1.05, the gluon condensates cause a decrease of the moment ratio, which results in change of spectral properties. Using the Breit-Wigner form for the phenomenological side, we find that mass shift of J/psi just above Tc can reach maximally 200 MeV and width can broaden to dozens of MeV.Comment: 4 pages, 5 figures, version to appear in Physical Review Letter

Aharonov-Casher phase and persistent current in a polyacetylene ring

We investigate a polyacetylene ring in an axially symmetric, static electric field with a modified SSH Hamiltonian of a polyacetylene chain. An effective gauge potential of the single electron Hamiltonian due to spin-field interaction is obtained and it results in a Fr\"{o}hlich's type of superconductivity equivalent to the effect of travelling lattice wave. The total energy as well as the persistent current density are shown to be a periodic function of the flux of the gauge field embraced by the polyacetylene ring.Comment: 12 pages, 5 figure

Does the 2D Hubbard Model Really Show d-Wave Superconductivity?

Some issues concerning the question if the two-dimensional Hubbard model really show d-wave superconductivity are briefly discussed.Comment: Revtex, no figure

Critical behavior of charmonia across the phase transition: A QCD sum rule approach

We investigate medium-induced change of mass and width of J/psi and eta_c across the phase transition in hot gluonic matter using QCD sum rules. In the QCD sum rule approach, the medium effect on heavy quarkonia is induced by the change of both scalar and twist-2 gluon condensates, whose temperature dependences are extracted from the lattice calculations of energy density and pressure. Although the stability of the operator product expansion side seems to break down at T > 1.06Tc for the vector channel and T>1.04Tc for the pseudoscalar channel, we find a sudden change of the spectral property across the critical temperature Tc, which originates from an equally rapid change of the scalar gluon condensate characterized by e-3p. By parameterizing the ground state of the spectral density by the Breit-Wigner form, we find that for both J/psi and eta_c, the masses suddenly decrease maximally by a few hundreds of MeV and the widths broaden to ~100 MeV slightly above Tc. Implications for recent and future heavy ion experiments are discussed. We also carry out a similar analysis for charmonia in nuclear matter, which could serve as a testing ground for observing the precursor phenomena of the QCD phase transition. We finally discuss the possibility of observing the mass shift at nuclear matter at the FAIR project at GSI.Comment: 18 pages, 21 figures, 2 figures are added and discussion on effect of dynamical quarks is extended. version to appear in Phys.Rev.

Spin-Orbit Coupling and Ion Displacements in Multiferroic TbMnO3

The electronic and magnetic properties of TbMnO3 leading to its ferroelectric (FE) polarization were investigated on the basis of relativistic density functional theory (DFT) calculations. In agreement with experiment, we show that the spin-spiral plane of TbMnO3 can be either the bc- or ab-plane, but not the ac-plane. As for the mechanism of FE polarization, our work reveals that the "pure electronic" model by Katsura, Nagaosa and Balatsky (KNB) is inadequate in predicting the absolute direction of FE polarization. For the ab-plane spin-spiral state of TbMnO3, the direction of FE polarization predicted by the KNB model is opposite to that predicted by DFT calculations. In determining the magnitude and the absolute direction of FE polarization in spin-spiral states, it is found crucial to consider the displacements of the ions from their ecntrosymmetric positions

Compensation of compliance errors in parallel manipulators composed of non-perfect kinematic chains

The paper is devoted to the compliance errors compensation for parallel manipulators under external loading. Proposed approach is based on the non-linear stiffness modeling and reduces to a proper adjusting of a target trajectory. In contrast to previous works, in addition to compliance errors caused by machining forces, the problem of assembling errors caused by inaccuracy in the kinematic chains is considered. The advantages and practical significance of the proposed approach are illustrated by examples that deal with groove milling with Orthoglide manipulator.Comment: Advances in Robot Kinematics, France (2012