9,168 research outputs found
Physical results from 2+1 flavor Domain Wall QCD
We review recent results for the chiral behavior of meson masses and decay
constants and the determination of the light quark masses by the RBC and UKQCD
collaborations. We find that one-loop SU(2) chiral perturbation theory
represents the behavior of our lattice data better than one-loop SU(3) chiral
perturbation theory in both the pion and kaon sectors.
The simulations have been performed using the Iwasaki gauge action at two
different lattice spacings with the physical spatial volume held approximately
fixed at (2.7 fm)^3. The Domain Wall fermion formulation was used for the 2+1
dynamical quark flavors: two (mass degenerate) light flavors with masses as
light as roughly 1/5 the mass of the physical strange quark mass and one
heavier quark flavor at approximately the value of the physical strange quark
mass.
On the ensembles generated with the coarser lattice spacing, we obtain for
the physical average up- and down-quark and strange quark masses
m_ud(MSbar,2GeV)=3.72(0.16)_stat(0.33)_ren(0.18)_syst MeV and
m_s(MSbar,2GeV)=107.3(4.4)_stat(9.7)_ren(4.9)_syst MeV, respectively, while we
find for the pion and kaon decay constants f_pi=124.1(3.6)_stat(6.9)_syst MeV,
f_K=149.6(3.6)_stat(6.3)_syst MeV. The analysis for the finer lattice spacing
has not been fully completed yet, but we already present some first
(preliminary) results.Comment: 7 pages, 3 figures, 1 table, talk presented at the XXVI International
Symposium on Lattice Field Theory, 14-19 July 2008, Williamsburg, VA, US
Updating algorithms with multi-step stochastic correction
Nested multi-step stochastic correction offers a possibility to improve
updating algorithms for numerical simulations of lattice gauge theories with
fermions. The corresponding generalisations of the two-step multi-boson (TSMB)
algorithm as well as some applications with hybrid Monte Carlo (HMC) algorithms
are considered.Comment: 10 pages; discussion extende
Seismic cycles, size of the largest events, and the avalanche size distribution in a model of seismicity
We address several questions on the behavior of a numerical model recently
introduced to study seismic phenomena, that includes relaxation in the plates
as a key ingredient. We make an analysis of the scaling of the largest events
with system size, and show that when parameters are appropriately interpreted,
the typical size of the largest events scale as the system size, without the
necessity to tune any parameter. Secondly, we show that the temporal activity
in the model is inherently non-stationary, and obtain from here justification
and support for the concept of a "seismic cycle" in the temporal evolution of
seismic activity. Finally, we ask for the reasons that make the model display a
realistic value of the decaying exponent in the Gutenberg-Richter law for
the avalanche size distribution. We explain why relaxation induces a systematic
increase of from its value observed in the absence of
relaxation. However, we have not been able to justify the actual robustness of
the model in displaying a consistent value around the experimentally
observed value .Comment: 11 pages, 10 figure
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