High Resolution Rapid Response observations of compact radio sources with the Ceduna Hobart Interferometer (CHI)

Context. Frequent, simultaneous observations across the electromagnetic spectrum are essential to the study of a range of astrophysical phenomena including Active Galactic Nuclei. A key tool of such studies is the ability to observe an object when it flares i.e. exhibits a rapid and significant increase in its flux density. Aims. We describe the specific observational procedures and the calibration techniques that have been developed and tested to create a single baseline radio interferometer that can rapidly observe a flaring object. This is the only facility that is dedicated to rapid high resolution radio observations of an object south of -30 degrees declination. An immediate application is to provide rapid contemporaneous radio coverage of AGN flaring at {\gamma}-ray frequencies detected by the Fermi Gamma-ray Space Telescope. Methods. A single baseline interferometer was formed with radio telescopes in Hobart, Tasmania and Ceduna, South Australia. A software correlator was set up at the University of Tasmania to correlate these data. Results. Measurements of the flux densities of flaring objects can be made using our observing strategy within half an hour of a triggering event. These observations can be calibrated with amplitude errors better than 15%. Lower limits to the brightness temperatures of the sources can also be calculated using CHI.Comment: 6 pages, 6 figures, 1 table. Accepted for publication in A&

Comparing Wilson and Clover Quenched SU(3)SU(3) Spectroscopy with an Improved Gauge Action

We present results of quenched $SU(3)$ hadron spectroscopy comparing \order(a) improved Wilson (Clover) fermions with conventional Wilson fermions. The configurations were generated using an \order(a^2) improved 6-link $SU(3)$ pure gauge action at $\beta$'s corresponding to lattice spacings of $0.15$, $0.18$, $0.20$, $0.33$, and $0.43$ fm. We find evidence that fermionic scaling violations are consistent with \order(a^2) for Clover and \order(a) with a nonnegligible \order(a^2) term for standard Wilson fermions. This latter mixed ansatz makes a reliable continuum extrapolation problematic for Wilson fermions. We also find that the slope of the scaling violations is roughly $250 MeV$ for both Wilson and Clover fermions.Comment: 3 pages latex with 2 postscript figures. Talk presented at LATTICE96(spectrum

A novel quark-field creation operator construction for hadronic physics in lattice QCD

A new quark-field smearing algorithm is defined which enables efficient calculations of a broad range of hadron correlation functions. The technique applies a low-rank operator to define smooth fields that are to be used in hadron creation operators. The resulting space of smooth fields is small enough that all elements of the reduced quark propagator can be computed exactly at reasonable computational cost. Correlations between arbitrary sources, including multi hadron operators can be computed a posteriori without requiring new lattice Dirac operator inversions. The method is tested on realistic lattice sizes with light dynamical quarks.Comment: 14 pages, 9 figure

Quenched SU(3)SU(3) hadron spectroscopy using improved fermionic and gauge actions

We present results of quenched $SU(3)$ hadron spectroscopy using \order(a) improved Wilson fermions. The configurations were generated using an \order(a^2) improved 6-link $SU(3)$ pure gauge action at $\beta$'s corresponding to lattice spacings of $0.43$, $0.25$, $0.20$, $0.18$, and $0.15$ fm. We find evidence that fermionic scaling violations are consistent with \order(a^2) errors.Comment: 4 pages latex with 3 postscript figures. Corrected column heading in tabl

SCRI Results With the Tadpole-Improved Clover Action

We compare light hadron spectroscopy using the Wilson and Clover fermionic actions. We show that a Clover coefficient chosen using tadpole-improved tree-level perturbation theory effectively eliminates the O(a) discretization errors present in the Wilson action. We find that discretization errors in light spectroscopy for both the Wilson and Clover actions are characterized by an energy scale mu of about 200-300 MeV, indicating that these errors can be reduced to the 5% level by using the Clover action at an inverse lattice spacing of about 1.3 GeV.Comment: Talk presented at the International Workshop on Lattice QCD On Parallel Computers, University of Tsukuba, March 10-15 1997. 9 LaTex pages plus 6 postscript figures, uses espcrc2.st