High temperature meson propagators with domain-wall quarks

We study the chiral properties of domain-wall quarks at high temperatures on an ensemble of quenched configurations. Low lying eigenmodes of the Dirac operator are calculated and used to check the extent to which the Atiyah-Singer index theorem is obeyed on lattices with finite $N_5$. We calculate the connected and disconnected screening propagators for the lowest mass scalar and pseudoscalar mesons in the sectors of different topological charge and note that they behave as expected. Separating out the would-be zero eigenmodes enables us to accurately estimate the disconnected propagators with far less effort than would be needed otherwise.Comment: LATTICE99(Finite Temperature and Density), 3 pages, 3 figure

Finite temperature QED3 with light fermions

Non-compact QED3 is simulated both in the quenched and unquenched cases. In particular, we investigate the restoration of chiral symmetry at finite temperature. We also compute the zero temperature spectrum of the theory, including (in the quenched case) the dynamical fermion mass. From these two set of data, one can obtain estimates for the ratio of the mass gap to the critical temperature, of particular interest for applications to high-Tc superconductivity.Comment: talk given at lattice'92, 3 LaTeX pages (using espcrc.sty), figures available upon reques

Improving the staggered quark action to reduce flavour symmetry violations

We investigate a class of actions for lattice QCD with staggered quarks aimed at reducing the flavour symmetry violations associated with using staggered fermions. These actions replace the gauge field link fields in the quark action with covariantly smeared fields. As such they are an extension of actions considered by the MILC collaboration. We show that such actions systematically reduce flavour symmetry violations in the weak coupling limit. Using the mass splitting between Goldstone and non-Goldstone pions as a measure of flavour symmetry violations we find that these actions have considerably less flavour symmetry violations than the standard staggered action, and represent an improvement on what can be achieved with the MILC action, on quenched configurations with $\beta=5.7$.Comment: 3 pages, Latex using espcrc2.sty. 1 coloured postscript figure included with epsffile. Talk presented by D.K.Sinclair at LATTICE'97, Edinburgh, Scotlan

Thermodynamics of Lattice QCD with massless quarks and chiral 4-fermion interactions

We have simulated lattice QCD with an irrelevant 4-fermion interaction and 2 zero mass quarks. The chiral phase transition is observed to be second order and we discuss extraction of critical exponents.Comment: LATTICE98(hightemp

QED on a momentum lattice

We investigate the possibility of doing momentum space lattice simulations as an alternative to the conventional method. The procedure is introduced and tested for quenched QED2 and quenched QED3. Interesting physical applications to unquenched QED3 and quenched QED4 are also briefly discussed.Comment: 3 pages, To appear in the proceedings of the LATTICE'93 conference, ILL-(TH)-93-2

Manifestations of the axial anomaly in finite temperature QCD

We compute the flavor singlet meson correlators and screening masses in quenched and $N_f=2$ QCD at $N_t=8$. The consequences of our results for the realization of the $U_A(1)$ symmetry at finite T are discussed and an interpretation of our measurements in terms of the behaviour of the low lying fermionic modes is proposed.Comment: Talk presented at LATTICE96(chirality in QCD

Finite ma corrections for sea quark matrix elements

We discuss the finite $ma$ corrections associated with the computation of sea quark matrix elements. We find them to differ from the standard normalization used for valence quarks and to depend strongly on the Lorentz structure of the current under consideration. Phenomenological implications of these results are briefly discussed in two examples. We also mention how the magnitude of the correction factors can be reduced by using a 2-link improved action.Comment: 3 pages, contribution to LATTICE'94, uuencoded compressed tar file (square root removed in equation (1)

Instantaneous Bethe-Salpeter equation: improved analytical solution

Studying the Bethe-Salpeter formalism for interactions instantaneous in the rest frame of the bound states described, we show that, for bound-state constituents of arbitrary masses, the mass of the ground state of a given spin may be calculated almost entirely analytically with high accuracy, without the (numerical) diagonalization of the matrix representation obtained by expansion of the solutions over a suitable set of basis states.Comment: 7 page

Topology, fermionic zero modes and flavor singlet correlators in finite temperature QCD

We extend our earlier results concerning the breaking of the U_A(1) symmetry in finite temperature QCD. In particular, we use topological arguments to investigate the chiral limit.Comment: 3 pages, Talk given at LATTICE'9