4,137 research outputs found
The Euler-Heisenberg Lagrangian beyond one loop
We review what is presently known about higher loop corrections to the
Euler-Heisenberg Lagrangian and its Scalar QED analogue. The use of those
corrections as a tool for the study of the properties of the QED perturbation
series is outlined. As a further step in a long-term effort to prove or
disprove the convergence of the N photon amplitudes in the quenched
approximation, we present a parameter integral representation of the three-loop
Euler-Heisenberg Lagrangian in 1+1 dimensional QED, obtained in the worldline
formalism.Comment: 11 pages, 2 figures, talk given by Christian Schubert at QFEXT11,
Benasque, Spain, Sept. 18-24, 2011, to appear in the conference proceeding
FQHE interferometers in strong tunneling regime. The role of compactness of edge fields
We consider multiple-point tunneling in the interferometers formed between
edges of electron liquids with in general different filling factors in the
regime of the Fractional Quantum Hall effect (FQHE). We derive an effective
matrix Caldeira-Leggett models for the multiple tunneling contacts connected by
the chiral single-mode FQHE edges. It is shown that the compactness of the Wen-
Fr\"ohlich chiral boson fields describing the FQHE edge modes plays a crucial
role in eliminating the spurious non-locality of the electron transport
properties of the FQHE interferometers arising in the regime of strong
tunneling.Comment: 5 page
Comment on soft-pion emission in DVCS
The soft-pion theorem for pion production in deeply virtual Compton
scattering, derived by Guichon, Mosse and Vanderhaegen, is shown to be
consistent with chiral perturbation theory. Chiral symmetry requires that the
nonsinglet operators corresponding to spin-independent and spin-dependent
parton distributions have the same anomalous dimensions in cases where those
operators are related by chiral transformations. In chiral perturbation theory,
their scale-dependences can thus be absorbed in the coefficents of the
corresponding effective operators, without affecting their chiral structures.Comment: 2 pages, RevTe
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