Fri·Sep 14, 2007Friday·September 14, 2007

1. 01*

   Pion Polarizabilities and Volume Effects in Lattice QCD

   Jie Hu🇺🇸 · Fu-Jiun Jiang🇨🇭 · Brian C. Tiburzi🇺🇸

   We use chiral perturbation theory to study the extraction of pion electromagnetic polarizabilities from lattice QCD. Chiral extrapolation formulae are derived for partially quenched QCD, and quenched QCD simulations. On a torus, volume dependence of electromagnetic observables is complicated by SO(4) breaking, as well as photon zero-mode interactions. We determine finite volume corrections to the Compton scattering tensor of pions. We argue, however, that such results cannot be used to ascertain volume corrections to polarizabilities determined in lattice QCD with background field methods. Connection is lacking because momentum expansions are not permitted in finite volume. Our argument also applies to form factors. Volume effects for electromagnetic moments cannot be deduced from finite volume form factors.

   hep-lathep-phnucl-thPRD(2008)·22 citations
2. 02*

   Infrared Gluon and Ghost Propagators

   Marco Frasca🇮🇹

   We derive the form of the infrared gluon propagator by proving a mapping in the infrared of the quantum Yang-Mills and $\lambda {\varphi }^4$ theories. The equivalence is complete at a classical level. But while at a quantum level, the correspondence is spoiled by quantum fluctuations in the ultraviolet limit, we prove that it holds in the infrared where the coupling constant happens to be very large. The infrared propagator is then obtained from the quantum field theory of the scalar field producing a full spectrum. The results are in fully agreement with recent lattice computations. We get a finite propagator at zero momentum, the ghost propagator going to infinity as $1/p^{2+2\kappa }$ with $\kappa =0$.

   ↳ hep-thhep-lathep-phmath-ph+2PLB(2008)·94 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.