A small-parameter approach for few-body problems

A procedure to solve few-body problems is developed which is based on an expansion over a small parameter. The parameter is the ratio of potential energy to kinetic energy for states having not small hyperspherical quantum numbers, K>K ₀. Dynamic equations are reduced perturbatively to equations in the finite-dimension subspace with K ⩽ K ₀. Contributions from states with K>K ₀ are taken into account in a closed form, i.e., without an expansion over basis functions. Estimates concerning the efficiency of the approach are presented. The text was submitted by the author in English.