Quenched fermions on the Columbia lattice parallel processor (original) (raw)
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The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
Large scale QCD Monte Carlo calculations have typically been performed on either commercial supercomputers or specially built massively parallel computers such as Fermilab’s ACPMAPS. Commodity computer systems offer impressive floating point performance-tocost ratios which exceed those of commercial supercomputers. As high performance networking components approach commodity pricing, it becomes reasonable to assemble a massively parallel supercomputer from commodity parts. We describe the work and progress to date of a collaboration working on this problem.
Hadron spectrum, quark masses, and decay constants from light overlap fermions on large lattices
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We present results from a simulation of quenched overlap fermions with Lüscher-Weisz gauge field action on lattices up to 24 3 48 and for pion masses down to ≈ 250 MeV. Among the quantities we study are the pion, rho and nucleon masses, the light and strange quark masses, and the pion decay constant. The renormalization of the scalar and axial vector currents is done nonperturbatively in the RI − M OM scheme. The simulations are performed at two different lattice spacings, a ≈ 0.1 fm and ≈ 0.15 fm, and on two different physical volumes, to test the scaling properties of our action and to study finite volume effects. We compare our results with the predictions of chiral perturbation theory and compute several of its low-energy constants. The pion mass is computed in sectors of fixed topology as well.
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Nuclear Physics B - Proceedings Supplements, 1988
We report on a calculation of the hadronic mass spectrum and QC~-potential which incorporates the effects of the virtual quark-antiquark pairs, at a coupling of 0 = 5.7, quark masses of .10, .05 and .02, on a 10 s x s2 lattice. The effects of the dynamical quarks were implemented with the pseudofermion algorithm. The results will be compared with those obtained in the quenched approximation.
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Our progress in computing the spectrum of excited baryons and mesons in lattice QCD is described. Sets of spatially-extended hadron operators with a variety of different momenta are used. A new method of stochastically estimating the low-lying effects of quark propagation is utilized which allows reliable determinations of temporal correlations of both single-hadron and multi-hadron operators. The method is tested on the isoscalar mesons in the scalar, pseudoscalar, and vector channels, and on the two-pion system of total isospin I = 0, 1, 2.
Static hadron properties in lattice QCD
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We calculate hadron masses and magnetic moments in the quenched approximation to lattice QCD, using Monte Carlo and Gauss-Seidel methods. For the mass computation, we have quite good statistics; in addition, our lattice is long enough in the “time” direction to make a rather clear separation of the lowest lying hadrons from their radial excitations. We find mass ratios which are far from the experimental values; there is evidence that this may be due to the small spatial size of the lattice (which, however, is as large or larger than that used in most previous computations). For the magnetic moments, the situation is somewhat better, presumably because the moment calculation is really a qualitative test of the constituent quark model.
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Physical Review D, 2004
We study SU (3) gluon electric and magnetic masses at finite temperatures using quenched lattice QCD on a 20 2 × 32 × 6 lattice. We focus on temperature regions between T = Tc and 6Tc, which are realized in BNL Relativistic Heavy Ion Collider and CERN Large Hadron Collider experiments. Stochastic quantization with a gauge-fixing term is employed to calculate gluon propagators. The temperature dependence of the electric mass is found to be consistent with the hard-thermal-loop perturbation, and the magnetic mass has finite values in the temperature region of interest. Both screening masses have little gauge parameter dependence. The behavior of the gluon propagators is very different in confinement/deconfinement physics. The short distance magnetic part behaves like a confined propagator even in the deconfinement phase. A simulation with a larger lattice, 32 2 × 48 × 6, shows that the magnetic mass has a stronger finite size effect than the electric mass.
Tuning the strange quark mass in lattice simulations
Physics Letters B, 2010
QCD lattice simulations with 2+12+1 flavours typically start at rather large up-down and strange quark masses and extrapolate first the strange quark mass to its physical value and then the up-down quark mass. An alternative method of tuning the quark masses is discussed here in which the singlet quark mass is kept fixed, which ensures that the kaon always has mass less than the physical kaon mass. It can also take into account the different renormalisations (for singlet and non-singlet quark masses) occurring for non-chirally invariant lattice fermions and so allows a smooth extrapolation to the physical quark masses. This procedure enables a wide range of quark masses to be probed, including the case with a heavy up-down quark mass and light strange quark mass. Results show the correct order for the baryon octet and decuplet spectrum and an extrapolation to the physical pion mass gives mass values to within a few percent of their experimental values.