Infrared behavior of the Faddeev-Popov operator in Coulomb gauge QCD

We calculate the eigenvalue distribution of the Faddeev-Popov operator in Coulomb gauge QCD using quenched SU(3) lattice simulation. In the confinement phase, the density of the low-lying eigenvalues increases with lattice volume, and the confinement criterion is satisfied. Moreover, even in the deconfinement phase, the behavior of the FP eigenvalue density is qualitatively the same as in the confinement phase. This is consistent with the fact that the color-Coulomb potential is not screened in the deconfined phase.Comment: 10 pages, 10 figure

Scaling study of the gluon propagator in Coulomb gauge QCD on isotropic and anisotropic lattices

We calculate the transverse and time-time components of the instantaneous gluon propagator in Coulomb gauge QCD by using an SU(3) quenched lattice simulation on isotropic and anisotropic lattices. We find that the gluon propagators suffer from strong discretization effects on the isotropic lattice; on the other hand, those on the anisotropic lattices give a better scaling. Moreover, on these two type of lattices the transverse parts are significantly suppressed in the infrared region and have a turnover at about 500 [MeV]. The high resolution to the temporal direction due to the anisotropy yields small discretization errors for the time-time gluon propagators, which also show an infrared enhancement as expected in the Gribov-Zwanziger confinement scenario.Comment: 29 pages, 18 figure

Spectral sum for the color-Coulomb potential in SU(3) Coulomb gauge lattice Yang-Mills theory

We discuss the essential role of the low-lying eigenmodes of the Faddeev-Popov (FP) ghost operator on the confining color-Coulomb potential using SU(3) quenched lattice simulations in the Coulomb gauge. The color-Coulomb potential is expressed as a spectral sum of the FP ghost operator and has been explored by partially summing the FP eigenmodes. We take into account the Gribov copy effects that have a great impact on the FP eigenvalues and the color-Coulomb potential. We observe that the lowest eigenvalue vanishes in the thermodynamic limit much faster than that in the Landau gauge. The color-Coulomb potential at large distances is governed by the near-zero FP eigenmodes; in particular, the lowest one accounts for a substantial portion of the color-Coulomb string tension comparable to the Wilson string tension.Comment: 14 pages, 14 figure

Properties of Color-Coulomb String Tension

We study the properties of the color-Coulomb string tension obtained from the instantaneous part of gluon propagators in Coulomb gauge using quenched SU(3) lattice simulation. In the confinement phase, the dependence of the color-Coulomb string tension on the QCD coupling constant is smaller than that of the Wilson loop string tension. On the other hand, in the deconfinement phase, the color-Coulomb string tension does not vanish even for $T/T_c = 1 \sim 5$, the temperature dependence of which is comparable with the magnetic scaling, dominating the high temperature QCD. Thus, the color-Coulomb string tension is not an order parameter of QGP phase transition.Comment: 17 pages, 5 figures; one new figure added, typos corrected, version to appear in PR

Prediction of Ferromagnetic Ground State of NaCl-type FeN

Ab-initio results for structural and electronic properties of NaCl-type FeN are presented in a framework of plane-wave and ultrasoft pseudopotentials. Competition among different magnetic ordering is examined. We find the ferromagnetic phase stable overall. Stabilization over the unpolarized phase is obtained by splitting one flat t_2g-type band crossing the Fermi energy. A comparison with CrN is considered. We find large differences in the properties of the two systems that can be addressed to the smaller ionicity and magnetization of FeN.Comment: 5 pages, 4 figures, twocolumn latex style Sentence changed in Section III line 1

Electronic structure and magnetism of equiatomic FeN

In order to investigate the phase stability of equiatomic FeN compounds and the structure-dependent magnetic properties, the electronic structure and total energy of FeN with NaCl, ZnS and CsCl structures and various magnetic configurations are calculated using the first-principles TB-LMTO-ASA method. Among all the FeN phases considered, the antiferromagnetic NaCl structure with q=(00pi) is found to have the lowest energy at the theoretical equilibrium volume. However, the FM NaCl phase lies only 1mRyd higher. The estimated equilibrium lattice constant for nonmagnetic ZnS-type FeN agrees quite well with the experimental value, but for the AFM NaCl phase the estimated value is 6.7% smaller than that observed experimentally. For ZnS-type FeN, metastable magnetic states are found for volumes larger than the equilibrium value. On the basis of an analysis of the atom- and orbital-projected density of states and orbital-projected Crystal Orbital Hamilton Population, the iron-nitrogen interactions in NM ZnS, AFM NaCl and FM CsCl structures are discussed. The leading Fe-N interactions is due to the d-p iron-nitrogen hybridization, while considerable s-p and p-p hybridizations are also observed in all three phases. The iron magnetic moment in FeN is found to be highly sensitive to the nearest-neighboring Fe-N distance. In particular, the magnetic moment shows an abrupt drop from a value of about 2 muB to zero with the reduction of the Fe-N distance for the ZnS and CsCl structures.Comment: 12 pages, 6 figure

Continuous Avalanche Segregation of Granular Mixtures in Thin Rotating Drums

We study segregation of granular mixtures in the continuous avalanche regime (for frequencies above ~ 1 rpm) in thin rotating drums using a continuum theory for surface flows of grains. The theory predicts profiles in agreement with experiments only when we consider a flux dependent velocity of flowing grains. We find the segregation of species of different size and surface properties, with the smallest and roughest grains being found preferentially at the center of the drum. For a wide difference between the species we find a complete segregation in agreement with experiments. In addition, we predict a transition to a smooth segregation regime - with an power-law decay of the concentrations as a function of radial coordinate - as the size ratio between the grains is decreased towards one.Comment: 4 pages, 4 figures, http://polymer.bu.edu/~hmaks

Astrometry of OH/IR stars using 1612 MHz hydroxyl masers. I. Annual parallaxes of WX Psc and OH138.0+7.2

We report on the measurement of the trigonometric parallaxes of 1612 MHz hydroxyl masers around two asymptotic giant branch stars, WX Psc and OH138.0+7.2, using the NRAO Very Long Baseline Array with in-beam phase referencing calibration. We obtained a 3-sigma upper limit of <=5.3 mas on the parallax of WX Psc, corresponding to a lower limit distance estimate of >~190 pc. The obtained parallax of OH138.0+7.2 is 0.52+/-0.09 mas (+/-18%), corresponding to a distance of 1.9(+0.4,-0.3) kpc, making this the first hydroxyl maser parallax below one milliarcsecond. We also introduce a new method of error analysis for detecting systematic errors in the astrometry. Finally, we compare our trigonometric distances to published phase-lag distances toward these stars and find a good agreement between the two methods.Comment: Preprint, accepted for publication in The Astronomical Journal (January 17, 2017