Structure of the grope filtration of the knot concordance group
SPEAKER | Taehee Kim
DATE | May 10(Wed), 2017
TIME | 11:20
PLACE | 8101
ABSTRACT | A grope in the 4-ball bounded by a knot in the 3-sphere is a certain 2-complex which can be considered as an approximation of a slice disk. Cochran, Orr, and Teichner defined a filtration of the knot concordance group using gropes. In this talk, I will give a new infinite rank subgroup for each of the successive quotients of the filtration. A key ingredient is L2-signature defects associated to amenable groups.