Topology and chiral symmetry in finite temperature QCD

We investigate the realization of chiral symmetry in the vicinity of the deconfinement transition in quenched QCD using overlap fermions. Via the index theorem obeyed by the overlap fermions, we gain insight into the behavior of topology at finite temperature. We find small eigenvalues, clearly separated from the bulk of the eigenvalues, and study the properties of their distribution. We compare the distribution with a model of a dilute gas of instantons and anti-instantons and find good agreement.Comment: 3 pages with 3 ps figures; to appear in the proceedings of Lattice '99, Pisa, Italy, June 29 -- July 3, 1999. LATTICE99(topology

Thermodynamics with Dynamical Clover Fermions

We investigate the finite temperature behavior of nonperturbatively improved clover fermions on lattices with temporal extent N_t=4 and 6. Unfortunately in the gauge coupling range, where the clover coefficient has been determined nonperturbatively, the finite temperature crossover/transition occurs at heavy pseudoscalar masses and large pseudoscalar to vector meson mass ratios. However, on an N_t=6 lattice the thermal crossover for the improved fermions is much smoother than for unimproved Wilson fermions and no strange metastable behavior is observed.Comment: 8 pages, LaTeX, 5 postscript figure

Probing the QCD vacuum with overlap fermions

We use low lying eigenvectors of the overlap-Dirac operator as a probe of the QCD vacuum. If instantons play a significant role one would expect the low lying eigenmodes of the overlap-Dirac operator to consist mainly of the mixed ``would be zero modes''. Then, the eigenmodes should exhibit local chirality. Studying a recently introduced local chirality parameter, we find evidence supporting this picture.Comment: LaTeX, 5 pages, 5 postscript figures. Talk given by U.M. Heller at the Workshop on Lattice Hadron Physics ``LHP2001'', July 9 -- 18, 2001, Cairns, Australi

Overlap Dirac Operator, Eigenvalues and Random Matrix Theory

The properties of the spectrum of the overlap Dirac operator and their relation to random matrix theory are studied. In particular, the predictions from chiral random matrix theory in topologically non-trivial gauge field sectors are tested.Comment: 3 pages latex with 1 postscript figure. Talk presented at LATTICE99(topology

Magnetization of a half-quantum vortex in a spinor Bose-Einstein condensate

Magnetization dynamics of a half-quantum vortex in a spin-1 Bose-Einstein condensate with a ferromagnetic interaction are investigated by mean-field and Bogoliubov analyses. The transverse magnetization is shown to break the axisymmetry and form threefold domains. This phenomenon originates from the topological structure of the half-quantum vortex and spin conservation.Comment: 6 pages, 3 figure