Title: Hassett moduli stacks of twisted maps

Abstract: A stable n-marked curve is a nodal curve with n distinct marked points and finitely many automorphisms. If we choose rational numbers a_1, . . ., a_n in the interval (0, 1], then a weighted stable n-marked curve is a generalization where the marks are allowed to coincide as long as the total weight at any point is at most one. Moduli of weighted stable curves were first constructed by Hassett. On the other hand, a twisted stable n-marked curve is a tame stack whose coarse moduli space is a stable n-marked curve, such that stacky structure is concentrated at nodes and markings and has a specific local description. I will discuss a modification (using log geometry) of the moduli of twisted stable curves where the markings are allowed to coincide, analogous to Hassett's construction for representable curves. When we add the data of a representable morphism to a target, this construction lets us contract genus-zero subcurves of the domain that factor through a (stacky) point, and leads to a smaller modular compactification of orbifold stable maps with smooth source curves. This is a joint work with Martin Olsson.