60,322 research outputs found
The gradient flow in a twisted box
We study the perturbative behavior of the gradient flow in a twisted box. We
apply this information to define a running coupling using the energy density of
the flow field. We study the step-scaling function and the size of cutoff
effects in SU(2) pure gauge theory. We conclude that the twisted gradient flow
running coupling scheme is a valid strategy for step-scaling purposes due to
the relatively mild cutoff effects and high precision.Comment: LaTeX. 7 pages. Proceedings of the 31st International Symposium on
Lattice Field Theory - LATTICE 2013. July 29 - August 3, 2013. Mainz, German
FK/Fpi in full QCD
We determine the ratio FK/Fpi in QCD with Nf=2+1 flavors of sea quarks, based
on a series of lattice calculations with three different couplings, large
volumes and a simulated pion mass reaching down to about 190 MeV. We obtain
FK/Fpi = 1.192 +- 0.007(stat) +- 0.006(sys) with all the sources of systematic
uncertainty under control.Comment: 8 pages, 9 figures, 1 table. Presented at the XXVII International
Symposium on Lattice Field Theory (2009
A meta-analysis of the magnetic line broadening in the solar atmosphere
A multi-line Bayesian analysis of the Zeeman broadening in the solar
atmosphere is presented. A hierarchical probabilistic model, based on the
simple but realistic Milne-Eddington approximation to the solution of the
radiative transfer equation, is used to explain the data in the optical and
near infrared. Our method makes use of the full line profiles of a more than
500 spectral lines from 4000 to 1.8 m. Although the problem suffers
from a strong degeneracy between the magnetic broadening and any other
remaining broadening mechanism, the hierarchical model allows to isolate the
magnetic contribution with reliability. We obtain the cumulative distribution
function for the field strength and use it to put reliable upper limits to the
unresolved magnetic field strength in the solar atmosphere. The field is below
160-180 G with 90% probability.Comment: 9 pages, 6 figures, accepted for publication in A&A. Fixed reference
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