  We study the effects of finite-sizeness on small, neutrally buoyant,
spherical particles advected by open chaotic flows. We show that, when
projected onto configuration space, the advected finite-size particles disperse
about the unstable manifold of the chaotic saddle that governs the passive
advection. Using a discrete-time system for the dynamics, we obtain an
expression predicting the dispersion of the finite-size particles in terms of
their Stokes parameter at the onset of the finite-sizeness induced dispersion.
We test our theory in a system derived from a flow and find remarkable
agreement between our expression and the numerically measured dispersion.
