Friday, November 27, 2015 - 13:00
A finite-volume local formulation of QCD coupled to QED
Isospin breaking by QED interactions plays an important role in the standard model phenomenology. The lattice provides an ab-initio framework to compute hadron mass splittings due to QED effects. While calculations of these effects are already available, the most accurate results rely on a non-local formulation of QED at finite volume, known as QED$_L$. In a full first-principle approach, for this formulation, one would need to show that the violation of locality at finite volume does not result in subtleties that might generate hard to control systematic effects. As an alternative programme, in this talk, we analyse a formulation of QCD coupled to QED on a C*-periodic finite lattice, which is local. Finite size corrections to charged particle masses are shown to have a different functional form in our framework and turn out to be significantly smaller than in QED$_L$. The flavour and baryon symmetries are discussed both at finite lattice size and in the approach to the infinite volume limit. Gauge covariant expressions of electrically charged operators and a formulation of the theory on the lattice are also presented.