We derive a single-channel effective Kbar N interaction from chiral SU(3) coupled-channel dynamics, emphasizing the important role of the pi Sigma channel and the structure of the Lambda(1405) resonance. The chiral low energy theorem requires strongl
y attractive interaction not only in the Kbar N channel but also in the pi Sigma channel. As a consequence of the strong pi Sigma dynamics, the equivalent potential in single Kbar N channel turns out to be less attractive than the one used in a purely phenomenological approach.
We discuss several aspects of the Lambda(1405) resonance in relation to the recent theoretical developments in chiral dynamics. We derive an effective single-channel KbarK N interaction based on chiral SU(3) coupled-channel approach, emphasizing the
important role of the pi Sigma channel and the structure of the Lambda(1405) in Kbar N phenomenology. In order to clarify the structure of the resonance, we study the behavior with the number of colors (Nc) of the poles associated with the Lambda(1405), and argue the physical meaning of the renormalization procedure.
