Cofrontals

In this paper we introduce the notion of cofrontal mappings, as the dual objects to frontal mappings, and study their basic local and global properties. Cofrontals are very special mappings and far from generic nor stable except for the case of submersions. It is observed that any smooth mapping can be $C^0$-approximated by a possibly \lq\lq unfair" cofrontal or a frontal. However global “fair” cofrontals are very restrictive to exist. Then we give a method to construction “fair” cofrontals with fiber-dimension one and a target-local diffeomorphism classification of such cofrontals, under some finiteness condition.