Discrete Math Seminar: Stephanie van Willigenburg

The chromatic polynomial was generalized to the chromatic symmetric function by Stanley in his seminal 1995 paper. This function is currently experiencing a flourishing renaissance, in particular the study of the positivity of chromatic symmetric functions when expanded into the basis of elementary symmetric functions, that is, e-positivity.

In this talk we approach the question of e-positivity from various angles. Most pertinently we resolve the 1995 statement of Stanley that
no known graph exists that is not contractible to the claw, and whose chromatic symmetric function is not e-positive.

This is joint work with Soojin Cho, Samantha Dahlberg and Angele Foley, and no prior knowledge is assumed.