606 research outputs found
Effective string description of confining flux tubes
We review the current knowledge about the theoretical foundations of the
effective string theory for confining flux tubes and the comparison of the
predictions to pure gauge lattice data. A concise presentation of the effective
string theory is provided, incorporating recent developments. We summarize the
predictions for the spectrum and the profile/width of the flux tube and their
comparison to lattice data. The review closes with a short summary of open
questions for future research.Comment: 21 pages, 8 figures, Contribution to IJMPA special issue "Lattice
gauge theory beyond QCD
Antiscreening of the Ampere force in QED and QCD plasmas
The static forces between electric charges and currents are modified at the
loop level by the presence of a plasma. While electric charges are screened,
currents are not. The effective coupling constant at long distances is enhanced
in both cases as compared to the vacuum, and by different amounts, a clear sign
that Lorentz symmetry is broken. We investigate these effects quantitatively,
first in a QED plasma and secondly using non-perturbative simulations of QCD
with two light degenerate flavors of quarks.Comment: 17 pages, 8 figure
Calculation of the pion electromagnetic form factor from lattice QCD
We present a lattice calculation of the vector form factor of the pion for
two flavours of non-perturbatively O(a) improved Wilson fermions. For the
measurements we utilise the CLS ensembles which include various lattice
spacings and pion masses down to about 250 MeV. To obtain a fine momentum
resolution near zero momentum transfer (q^2) partially twisted boundary
conditions are employed using several twist angles. Due to the fine resolution
around q^2=0 we are able to determine the slope of the form factor and, in
turn, extract the charge radius of the pion without any model dependence. The
results for the form factor and the charge radius are then compared to chiral
perturbation theory and phenomenological models which are used to extrapolate
the results to the physical point.Comment: 4 pages, 4 figures, talk presented at Hadron 2011: 14th International
Conference on Hadron Spectroscopy, Munich, German
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