# Poster presented by Anna Hasenfratz

**Poster Session**
**Topic:** Topology and Confinement

### Instantons and Quarks in QCD

**Abstract:** There are two basic approaches to study instanton effects in lattice QCD. One can study instantons directly using a topological charge operator constructed from the gauge field. Alternately, one can consider the effect of instantons on the quarks and study them through the spectrum of the Dirac operator.In this talk I describe how the fermionic wave function can be used to identify the location and size of the instantons of the gauge configuration offering an alternative way to measure the instanton size distribution. This method avoids many of the problems encountered when measuring the instanton size distribution using the pure gauge topological density since no smoothing of the action is necessary with the fermions. Results for the instanton size distribution using fermions are consistent with our past results using pure gauge observables. Since no smoothing is necessary to identifying instantons using the fermion density, this method is ideal to study the structure of finite temperature dynamical lattices. Some preliminary results on finite temperature configurations will be presented.

Massimo Campostrini,
`campo@mailbox.difi.unipi.it`