ff-Racks, ff-quandles, their extensions and cohomology
Abstract
The purpose of this paper is to introduce and study the notions of ff-rack and ff-quandle which are obtained by twisting the usual equational identities by a map. We provide some key constructions, examples and classification of low order ff-quandles. Moreover, we define modules over ff-racks, discuss extensions and define a cohomology theory for ff-quandles and give examples.
Communicated by S. López-Permouth