Applications of Instanton Induced Quark Forces in Hadron Spectroscopy and Nuclear Physics

Abstract

Our present understanding of hadronic matter is obscured by the confinement problem; the fundamental constituents of hadrons should never appear as observable states and hence a relativistic theory of bound states must in principle stand at the beginning of any computation of hadronic reactions. The problem of formulating such a theory is by no means particular to QCD. So far, even for simpler field theories no practicable theory has been developed. By exploiting the fact that QCD is a gauge theory, the bound state problem of QCD can be studied by lattice calculations, but it is still questionable whether the extremely rich spectrum of mesons and baryons will be fmally obtained. At the moment, the link between QCD and low-energy hadron physics is given by phenomenological models only, and very few genuine QCD results enter in the corresponding model assumptions. In this contribution, we want to stress the possible role of an instanton induced quark force, both in hadron spectroscopy and intermediate energy nuclear physics. This solves none of the fundamental problems related to confinement, but seems to be an excellent candidate to produce the correct mass splitting in the observed resonance spectrum, once we have fixed an admittedly phenomenological confinement prescription; in particular, they help to understand the role of chiral invariance in quark models in a consistent way.