Two seemingly unrelated questions (the quest for natural logics of abstract elementary classes on the one hand, and the quest for logics adequate to model theory on the other hand) converge around the same combinatorial core: partition relations for scattered order types (due to Kómjath and Shelah). I will present recent results concerning the first question (and axiomatizing a.e.c.'s - joint work with Shelah) and the second question (joint work with Väänänen).

Bio: Andrés Villaveces is a mathematician, working at Universidad Nacional de Colombia in Bogotá. Villaveces earned his doctoral degree from the University of Wisconsin-Madison in 1996 under the supervision of Ken Kunen. He held a postdoctoral position at the Hebrew University of Jerusalem (1996-1997) and has been a visiting professor at Carnegie Mellon University (2002-2003) and at the University of Helsinki (2007 and 2015). His work centers on the model theory of Abstract Elementary Classes and its connections with set theory and other parts of logic and mathematics.