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 Fusion for the 24^3*12 lattice planned for some of our FY2011 runs give: 24 cores = 46 Gflops 48 cores = 95 Gflops 72 cores = 148 Gflops 96 cores = 220 Gflops 144 cores = 369 Gflops 288 cores = 784 Gflops Our actual runs planned for Fusion are on a 16^3*8 lattice running on 128 cores. For these runs the per-core performance is about 3 Gflops Current: undetermined amount Justification: The per core performance for the 16^3*8 runs is approximately 3 Gflops on 128 cores. Althought we have not performed such a detailed analysis as for the 24^3*12 lattice, presented above, we expect at worst a linear speedup from the minimum number of cores (8) to the maximum number of cores (128). This code/lattice size has been running effectively on Fusion since it was released to the user community. We will be concentrating on the 3-flavour runs at m=0.01, 0.005, leaving the m=0.0025 runs for Carver at NERSC. The larger lattice runs will be performed on the Crays at NERSC and NICS. This corresponds to having an average of 1 job running for 7500 hours (out of a total of 8784 hours) for the year, which is easy to achieve. Requested: 480000 A specific reason has been given: Our original request was for 960000 core-hours, so this would be the appropriate amount for the second half of this year (commencing 1st April). Since the first allocation was exhausted in early January, and a subsequent request was not acted upon I am requesting that this allocation be made available immediately so that our work can continue. This needs to be approved and the final allocation amount decided upon. Thank You, The LCRC Accounts System