Yun S. Song
Thursday, February 24
1131 Kemper Hall
3 :10-4:00 p.m.
Biology abounds with examples where graphical representations and combinatorics have proved very useful. Of particular interest to geneticists is the usage of trees to represent evolutionary histories of biological sequences. In this talk, we will consider some enumeration problems regarding various types of evolutionary trees. In particular, we will discuss some properties of the so-called subtree-prune-and-regraft (SPR) tree rearrangement operation on leaf-labeled rooted binary trees with either partially or totally ordered internal vertices. We will discuss some exact results concerning the unit-neighborhood U(T), defined as the set of trees one SPR operation away from a given tree T.