Our work involves a Wilson-like fermionic action specifically formulated for 3+1 anisotropic lattices. At tree-level, mass-dependent cutoff effects are confined to the temporal direction. By using a fine temporal lattice spacing, it is feasible to accurately simulate relativistic heavy-quark systems.
We are interested in tuning the parameters of this action beyond tree level, both non-perturbatively (see our paper in Phys. Rev. D) and using perturbation theory.
Simulating QCD on anisotropic lattices with dynamical quarks requires a simultaneous tuning of the 2 input anisotropy parameters for quark and gluon fields. This may be achieved nonperturbatively by interpolating between 3 or more simulation points with different input parameters.
Using the anisotropic quark action described above we have performed the first such tuning, and the process and results are are described in a Phys. Rev. D paper. The parameters obtained are being used for a number of other projects.
The fermionic quark matrix is decomposed into a low-mode truncated eigenvector spectrum with the complementary space estimated using a random-noise technique. This technique utilises the structure of the discrete quarkfield to reduce noise in the estimate ("dilution"). The algorithm gives the exact quark propagator in a finite (but large) amount of quark inversions. We are currently investigating optimal dilution paths for various operators and optimising the suite of code for user-independent performance.
A paper has been published in Comp.Phys.Commun.
We are studying the spectra of mesons and baryons containing a single heavy quark in Nf = 2 QCD with particular emphasis on orbitally excited states. We work in the static approximation where the heavy quark is assumed to be infinitely massive. Point propagator methods have traditionally yielded very poor results in the static limit and we are using all-to-all propagators on an anisotropic lattices to determine particle energies to a high precision.
We study in-medium modifications of spectral functions of charmonium and light vector mesons at high temperature, using anisotropic lattices with two flavours of dynamical fermions. The same lattices will also be used for studying pressure, energy and entropy density as functions of temperature without having to apply the integral method.
Collaborators: Giuseppe Burgio, Alessandra Feo, Mike Peardon, Sinéad Ryan
The perturbative analysis is complete, and a paper has been published in Phys.Rev.D.
We are investigating non-perturbative determination of the parameters in the action required to restore Euclidean invariance in long-distance correlations using the static potential.