Hello, A change in allocation has been requested: Requester: sinclair (Donald Sinclair) Project: Lattice-QCD Title: Lattice simulations of Conformal and Walking Technicolor. Description: We perform simulations to evaluate the functional integrals of QCD-like theories formulated on a discrete space-time lattice to enable determination of the non-perturbative aspects these theories. These include the properties of these theories at non-zero temperature including the scales of confinement and chiral symmetry breaking, and such zero temperature properties as spectra, decay constants and the running of the gauge coupling constant. We are particularly interested in those theories where the coupling constant evolves particularly slowly, since these are candidate 'Walking Technicolor' theories. Related to these are theories with an infrared fixed point. Of special interest is to differentiate these two different types of behaviour. We are performing simulations of QCD-like theories which are models for Walking or Conformal Technicolor. We have been studying theories which are essentially QCD but with colour-sextet rather than colour-triplet quarks. We hope to measure the running of the QCD coupling constant. For 2 or 3 flavours, 2-loop perturbation theory predicts an infrared fixed point. For 2 flavours, it is possible that a chiral condensate forms before this fixed point is reached. If so the fixed point is avoided, the theory is confining and chiral symmetry breaks spontaneously. However, there is a region where the coupling constant evolves very slowly. These are the properties required for a walking technicolor theory. Simulations we have performed so far at finite temperature suggest that this theory does indeed walk. This is an ongoing program at NERSC. We wish to run small-lattice simulations of the 3-flavour theory, which we expect to have conformal, rather than walking behaviour on Fusion, for comparison. If we are correct, the properties of the 2 and 3 flavour theories should look rather different. Our sextet quark codes are based on our earlier triplet quark codes and use the RHMC simulation method. The Rational Hybrid Monte Carlo (RHMC) is a stochastic molecular dynamics algorithm. The functional integral of QCD is written as a partition function of a classical field theory evolving in a fictitious time. The determinant of the Dirac operator raised to a fractional power is calculated by introducing bosonic fields (pseudofermions), and sandwiching this Dirac operator raised to minus said fractional power between them. This fractional power of the Dirac operator is approximated to machine accuracy by a rational approximation. After defining this this theory on a discrete space-time lattice, the inversions required by the partial-fraction expansion of the rational approximation are performed using Krylov space methods, in particular a multi-shift extension of the conjugate gradient algorithm. A global Metropolis Monte-Carlo accept/reject step applied at the end of each t rajectory removes discretization errors introduced by the numerical integration of these stochastic equations of motion. We parallelize the code by assigning a fixed number of adjacent lattice sites to each MPI task. Network bandwidth ultimately limits how small a chunk of the lattice can be assigned to each task. Benchmarks of this code on NERSC's Cray XT4 (Franklin) give 68 Gflops on 48 cores for a 12^3*4 lattice. This is a fortran code with the parallelization performed using MPI. Current: undetermined amount Justification: The CPU requirement is the estimated time required to perform finite temperature simulations of the 3-flavour theory on a 12^3*4 lattice, and is based on the CPU time which we used to perform our simulations on the same size lattice for 2 flavours on Franklin. This assumes that the code performance on Fusion and Franklin will be similar. We will also need to perform simulations on an 8^3*4 lattice, but expect this will be done during the break-in period. The reason we are proposing to perform this project on Fusion is that the other machines we have access to schedule jobs so as to discourage such small jobs as ours. Running these jobs on Fusion will allow us to run larger lattice simulations on these other platforms. We have benchmarked our 12^3*4 codes on Franklin and found the following performances on various numbers of CPUs 8 CPUs = 10 Gflops 12 CPUs = 17 Gflops 16 CPUs = 26 Gflops 24 CPUs = 41 Gflops 48 CPUs = 68 Gflops On 48 CPUs, the measured communication overhead is 47%, indicating that we are approaching the point where communications are becoming a bottleneck. Requested: 500000 A specific reason has been given: I am currently running low on resources and wish to try and complete the project on which I am working before the end of FY2010. This needs to be approved and the final allocation amount decided upon. Thank You, The LCRC Accounts System