Surface Maps into Free Groups

Citation

Walker, Alden Kent (2012) Surface Maps into Free Groups. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/FDRS-9S44. https://resolver.caltech.edu/CaltechTHESIS:05212012-102942842

Abstract

We exploit the combinatorial properties of surface maps into free groups to prove several new results in the field of stable commutator length and bounded cohomology. We show that random homomorphisms between free groups are isometries of scl; we prove interesting properties of the scl unit ball; we describe a transfer construction for quasimorphisms and give an infinite family of chains whose scl it certifies; we linearize the dynamics of endomorphisms on free groups and use this to prove that random endomorphisms can be realized by surface immersions, which provides many examples of surface subgroups of HNN extensions of free groups; and finally, we give an algorithm to compute scl in free products of finite or infinite cyclic groups that generalizes and improves previous work.

Thesis Files