Binding in velocity dependent potentials and pion-nuclear systems

Properties of bound states in velocity-dependent potentials are discussed and the WKB approximation is established and used to derive quantization conditions for such states. The most updated zero-range optical potential for pionic atoms is reviewed and employed for the calculation of strongly bound π^- nuclear states. Some of the several physical mechanisms, in particular the πN finite interaction range, which affect the whole issue of binding and critically determine the number of bound states expected, are qualitatively discussed. Unless dynamical suppression of π^- nuclear absorption occurs below threshold, the calculated states are too wide to be considered as well-defined physical states.