Extreme QCD 2017 - The 15th international workshop on QCD in eXtreme conditions

Topological susceptibility and Gribov copies

26 Jun 2017, 17:20

poster Poster session

Speaker

Caroline Felix (KU Leuven)

Description

The topological susceptibility, ${\chi }^4$, plays an important role in explaining the ${\eta }^{\prime }$ mass, the so-called $U(1{)}_A$ problem. For ${\chi }^4\ne 0$, we must have the Veneziano ghost, an unphysical massless pole in the correlation function of the topological current $K_{\mu }$ correlator. There was a recent attempt in http://inspirehep.net/record/1340323?ln= en to connect the dynamics of the Veneziano ghost, and thus topological susceptibility, with Gribov copies. However, we will discuss that this proposal is incompatible with BRST symmetry, following http://inspirehep.net/record/1402613?ln=en. We will also analyze the topological susceptibility in $SU(2)$ and $SU(3)$ Euclidean Yang-Mills theory in a generic linear covariant gauge taking into account the Gribov ambiguity, while keeping the BRST symmetry. During this analysis, we make use of a Pad{\' e} approximation based on the K\"all\'en-Lehmann spectral integral representation of the topological current correlation function.