  The effective Kbar N interaction based on chiral SU(3) coupled-channel
dynamics is derived and its extrapolation below the Kbar N threshold is studied
in detail. Starting from the coupled-channel scattering equations, we eliminate
the channels other than Kbar N and obtain an effective interaction in the
single Kbar N channel. An equivalent local potential in coordinate space is
constructed such as to reproduce the full scattering amplitude of the chiral
SU(3) coupled-channel framework. We discuss several realistic chiral
SU(3)-based models in comparison to reach conclusions about the uncertainties
involved. It turns out that, in the region relevant to the discussion of deeply
bound Kbar-nuclear few-body systems, the resulting energy-dependent, equivalent
local potential is substantially less attractive than the one suggested in
previous purely phenomenological treatments.
