Speaker:  Andy Frohmader
Title:  Flag f-vectors of colored complexes
Time: 2:30 PM, Monday, November 23, 2009
Place:  Malott 206

Abstract:  One can construct a simplicial complex on a set of colored vertices with the restriction that no two vertices of the same color can be in the same face. The flag f-numbers of the complex are the numbers of faces whose vertices are precisely a given color set, e.g., edges with exactly one red vertex and one blue vertex. It then makes sense to ask what possible collections of flag f-numbers a complex could have. More than twenty years ago, it was shown that three other characterization problems are equivalent to this one, but none of the problems have a known solution. We will explain why there cannot be a "nice" solution to this problem analogous to that of some similar problems in a particular sense, and then give a solution to the case of three colors.

November 17, 2009