A new definition for m-Cambrian lattices

The Cambrian lattices, introduced in (Reading, 2006), generalize the Tamari lattice to any choice of Coxeter element in any finite Coxeter group. They are further generalized to the m-Cambrian lattices (Stump, Thomas, Williams, 2015). However, their definitions do not provide a practical setup to work with combinatorially. In this paper, we provide a new equivalent definition of the m-Cambrian lattices on simple objects called m-noncrossing partitions, using a simple and effective comparison criterion. It is obtained by showing that each interval has a unique maximal chain that is c-increasing, which is computed by a greedy algorithm. Our proof is uniform, involving all Coxeter groups and all choices of Coxeter element at the same time. This work has been accepted as an extended abstract for the FPSAC 2025 conference. A long version of this work will be available later.