Date: October 29, 2014 Place: Online Logic Seminar, Moscow University Speaker: Stephen G. Simpson, Pennsylvania State University http://www.math.psu.edu/simpson/ Title: Gauging the complexity of mathematical theorems Abstract: Mathematical logic provides several frameworks for analyzing the "complexity" or "nonconstructivity" of a given mathematical theorem. Among these frameworks are: computable analysis, degrees of unsolvability, reverse mathematics, and algorithmic randomness. Each of these frameworks provides a different kind of information. In this talk I shall analyze a few nonconstructive mathematical theorems from each of these points of view.