On the sufficiency of <Emphasis Type="Italic">c</Emphasis>-cyclical monotonicity for optimality of transport plans

We consider a mass transport problem among Polish spaces, and we show that a transport plan concentrated in a c-cyclical monotone set is optimal if the cost function is continuous and possibly + ∞ valued; the same result is proved for a generic l.s.c. cost function in the case when the measures are purely atomic. This generalizes the previously known results.