2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48158Nonrelativistic two-body scattering by a short-ranged potential is studied using the renormalisation group. Two fixed points are identified: a trivial one and one describing systems with a bound state at zero energy. The eigenvalues of the linearised renormalisation group are used to assign a systematic power-counting to terms in the potential near each of these fixed points. The expansion around the nontrivial fixed point defines a power counting scheme which is equivalent to the effective-range expansion.11 pages (RevTeX), Talk given by K. Richardson at The 11th Summer School and Symposium on Nuclear Physics (NuSS'98) ``Effective Theories of Matter'', held in Seoul National University, June 23-26, 1998High Energy Physics - Phenomenologytext