Enumerating meandric systems with large number of loops
Résumé
We investigate meandric systems with a large number of loops using tools inspired by free probability. For any fixed integer r, we express the generating function of meandric systems on 2n points with n→r loops in terms of a finite (the size depends on r) subclass of irreducible meandric systems, via the moment-cumulant formula from free probability theory. We show that the generating function, after an appropriate change of variable, is a rational function, and we bound its degree. Exact expressions for the generating functions are obtained for r≤6, as well as the asymptotic behavior of the meandric numbers for general r.