Over the last 15 years, it has been noted that many combinatorial structures, such as real and complex hyperplane arrangements, interval greedoids, matroids, oriented matroids, and others have the structure of a left regular band, a certain kind of finite monoid. … Continue reading Colloquium: Monday, November 27, 4 pm. Speaker: Stuart W. Margolis (Bar Ilan). Title: “CW-decompositions, Leray numbers and the representation theory and cohomology of left regular band algebras”.