Unquenching the Schwinger Model (revised)

We study the quenched and unquenched lattice Schwinger model with Wilson fermions. The lowest non-trivial order of the systematic expansion recently proposed by Sexton and Weingarten is shown to allow good estimates of long distance physics from quenched configurations. Results for the static potential and the lowest bound state mass are presented.Comment: 4 pages, 2 figures, self-unpacking uuencoded compressed postscript Contribution to Lattice 95 [Revision: value corrected on p.3

The Numerical Estimation of the Error Induced by the Valence Approximation

We describe a systematic expansion for full QCD. The leading term in the expansion gives the valence approximation. The expansion reproduces full QCD if an infinite number of higher terms are included.Comment: 3 pages, latex, no figures, requires espcrc2.sty (included at end) Contribution to Lattice 94 proceeding

Approximate actions for dynamical fermions

Recent developments and applications of approximate actions for full lattice QCD are described. We present first results based on the stochastic estimation of the fermion determinant on $12^3\times 24$ configurations at $\beta=5.2$.Comment: 3 pages, Latex, no figures, Contribution to Lattice 97, The XV International Symposium on Lattice Field Theory, Edinburgh 22-26 July 199

Tuning Actions and Observables in Lattice QCD

We propose a strategy for conducting lattice QCD simulations at fixed volume but variable quark mass so as to investigate the physical effects of dynamical fermions. We present details of techniques which enable this to be carried out effectively, namely the tuning in bare parameter space and efficient stochastic estimation of the fermion determinant. Preliminary results and tests of the method are presented. We discuss further possible applications of these techniques.Comment: 17 pages, 4 eps figures; affiliation correction in this header + minor post-referee addition

INFLUENCE OF PHOSPHATE SOURCE ON VESICULAR-ARBUSCULAR MYCORRHIZAE OF \u3ci\u3eBOUTELOUA GRACILIS\u3c/i\u3e

Non-mycorrhizal and vesicular-arbuscular mycorrhizal Bouteloua gracilis infected with Glomus fasciculatus were grown in defined media containing different phosphate sources and compared with respect to phosphate content and form, biomass, chlorophyll concentration, and root phosphatase activity. The phosphate sources were sodium monobasic phosphate, a mixture of sodium monobasic phosphate and calcium phytate, and calcium phytate. Inositol and inositol plus calcium were added to the sodium phosphate medium as additional treatments. Mycorrhizal infection was highest in roots of plants grown in the presence of phytate (75%). Lower root infection levels were noted in plants from the sodium phosphate (19%) and mixed phosphate (22%) media. No penetration by fungi occurred in plants from the sodium phosphate plus inositol or inositol and calcium media. Dry wts of non-mycorrhizal plants were highest when grown in media containing phytate and sodium phosphate plus inositol and calcium followed in decreasing order by sodium phosphate plus inositol, mixed phosphates, and sodium phosphate. Mycorrhizal infection increased leaf dry wt in plants from the sodium phosphate medium and root dry wt from the phytate medium. Phosphate concentrations in the plants were highest when grown in mixed phosphate medium followed by sodium phosphate and phytate. Mycorrhizal infection always increased significantly leaf phosphate concentrations but increased root phosphate concentrations only in the phytate medium. Phosphates were found predominantly as organicallybound compounds in leaves of mycorrhizal plants whereas in leaves of non-mycorrhizal plants, most of the phosphate was inorganic. Chlorophyll concentrations increased significantly with mycorrhizal infection with no change in a/b ratios. Mycorrhizal plants grown in the phytate medium had substantially higher alkaline phosphatase activity than did non-mycorrhizal plants; acid phosphatase activity was not affected by mycorrhizal condition. These results suggest that form of the phosphate in the root environment influences naycorrhizal establishment and effect of mycorrhizae on plant growth

INFLUENCE OF PHOSPHATE SOURCE ON VESICULAR-ARBUSCULAR MYCORRHIZAE OF \u3ci\u3eBOUTELOUA GRACILIS\u3c/i\u3e

Non-mycorrhizal and vesicular-arbuscular mycorrhizal Bouteloua gracilis infected with Glomus fasciculatus were grown in defined media containing different phosphate sources and compared with respect to phosphate content and form, biomass, chlorophyll concentration, and root phosphatase activity. The phosphate sources were sodium monobasic phosphate, a mixture of sodium monobasic phosphate and calcium phytate, and calcium phytate. Inositol and inositol plus calcium were added to the sodium phosphate medium as additional treatments. Mycorrhizal infection was highest in roots of plants grown in the presence of phytate (75%). Lower root infection levels were noted in plants from the sodium phosphate (19%) and mixed phosphate (22%) media. No penetration by fungi occurred in plants from the sodium phosphate plus inositol or inositol and calcium media. Dry wts of non-mycorrhizal plants were highest when grown in media containing phytate and sodium phosphate plus inositol and calcium followed in decreasing order by sodium phosphate plus inositol, mixed phosphates, and sodium phosphate. Mycorrhizal infection increased leaf dry wt in plants from the sodium phosphate medium and root dry wt from the phytate medium. Phosphate concentrations in the plants were highest when grown in mixed phosphate medium followed by sodium phosphate and phytate. Mycorrhizal infection always increased significantly leaf phosphate concentrations but increased root phosphate concentrations only in the phytate medium. Phosphates were found predominantly as organicallybound compounds in leaves of mycorrhizal plants whereas in leaves of non-mycorrhizal plants, most of the phosphate was inorganic. Chlorophyll concentrations increased significantly with mycorrhizal infection with no change in a/b ratios. Mycorrhizal plants grown in the phytate medium had substantially higher alkaline phosphatase activity than did non-mycorrhizal plants; acid phosphatase activity was not affected by mycorrhizal condition. These results suggest that form of the phosphate in the root environment influences naycorrhizal establishment and effect of mycorrhizae on plant growth

Parallel Tempering in Lattice QCD with O(a)-Improved Wilson Fermions

We present details of our investigation of the Parallel Tempering algorithm. We consider the application of action matching technology to the selection of parameters. We then present a simple model of the autocorrelations for a particular parallel tempered system. Finally we present numerical results from applying the algorithm to lattice QCD with O(a)-improved dynamical fermions with twin ensemble system

Instability in the molecular dynamics step of a hybrid Monte Carlo algorithm in dynamical fermion lattice QCD simulations

We investigate instability and reversibility within Hybrid Monte Carlo simulations using a non-perturbatively improved Wilson action. We demonstrate the onset of instability as tolerance parameters and molecular dynamics step sizes are varied. We compare these findings with theoretical expectations and present limits on simulation parameters within which a stable and reversible algorithm is obtained for physically relevant simulations. Results of optimisation experiments with respect to tolerance prarameters are also presented.Comment: RevTeX, Some results here were presented at Vielat 99, Vienna, Austria, Sept 1999 22 Pages, 10 figures, to be submitted to PR