The Chillingworth Class is a Signed Stable Length
arXiv:1310.2537 · doi:10.2140/agt.2015.15.1863
Abstract
An orientation is defined on a family of curve graphs on which the Torelli group acts. It is shown that the resulting signed stable length of an element of the Torelli group is a cohomology class. This cohomology class is half the dual of the contraction of the Johnson homomorphism, the socalled "Chillingworth class".
Changed definition of pre-image function to make it uppersemicontinuous. Diagrams and more background were added