Combinatorial Approaches to Exceptional Sequences for Weighted Projective Lines of Type $(p,q)$

Abstract

We provide a combinatorial description of morphisms in the coherent sheaf category ${\rm coh}\mbox{-}\mathbb{X}(p,q)$ over weighted projective line of type $(p,q)$ via a marked annulus. This leads to a geometric realization of exceptional sequences in ${\rm coh}\mbox{-}\mathbb{X}(p,q)$. As applications, we present a classification of complete exceptional sequences, an effective method for enlarging exceptional sequences, and a new proof of the transitivity of the braid group action on complete exceptional sequences. Besides, we offer a combinatorial description of tilting bundles via lattice paths and count the number of tilting sheaves in ${\rm coh}\mbox{-}\mathbb{X}(p,q)$, up to the Auslander-Reiten translation.