A potential between heavy-light mesons is extracted from quark correlation functions in the framework of quenched lattice QCD with Kogut-Susskind fermions. We show that the resulting potential is attractive at short distances. An analysis of the influence of the light quark mass on the interaction is performed.

An effective residual interaction for a meson-meson system is computed in lattice QCD. We describe the theoretical framework and present its application to the I = 2 channel S-wave interaction of the π-π system. Scattering phase shifts are also computed and compared to experimental results.

A method for the extraction of an e ective 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 employing a conjugate gradient algorithm for the light propagators. Due to the Pauli exclusion principle, the results for QED indicate the existence of a hard core, but for QCD there is strong attraction at small meson distances.

We extend our calculations with the second-order tree-level and tadpole improved next-nearest-neighbor action to meson-meson systems. Correlation matrices built from interpolating fields representing two pseudoscalar mesons (π-π) with relative momenta p are diagonalized, and the mass spectrum is extracted. Link variable fuzzing and operator smearing at both sinks and sources is employed. Calculations are presented for two values of the hopping parameter. The spectrum is used to discuss the residual interaction in the meson-meson system.