MESON-MESON INTERACTIONS - FROM STATIC TO DYNAMIC VALENCE QUARKS

A method for the extraction of an effective meson-meson potential from Green functions, which can be obtained from a lattice simulation, is presented. Simulations are carried out for compact QED and QCD in four dimensions using the quenched approximation and the hopping parameter expansion. In a further study, a heavy-light meson is considered empl oying a conjugate gradient algorithm for the light propagators. Due to the Pauli exclusion principle, the results for QED indicate the exist ence of a hard core, but for QCD there is strong attraction at small m eson distances.