Structures of cobordism-like modules induced from generic maps of codimension -2

The Reeb space of a smooth map whose codimension is minus is the space defined as the space of all connected components of inverse images. For generic maps such as Morse functions and their higher dimensional versions, they are polyhedra whose dimensions are equal to those of the target manifolds and which have simplicial structures compatible with (the canonical) simplicial structures of the source and the target manifolds, and in considerable cases they inherit fundamental and important invariants of source manifolds. In fact, Reeb spaces are fundamentall tools in the algebraic and differential topological theory of generic maps or the global singularity theory. As one of studies of global topological properties of Reeb spaces, Hiratuka and Saeki showed in 2013 that for generic maps or more precisely, maps compatible with simplicial structures of the manifolds, inducing simplicial structures on the Reeb spaces and having connected components of inverse images of regular values being not null-cobordant, the top-dimensional homology groups with appropriate coefficient rings of the Reeb spaces do not vanish. Later the author extended this theorem: the author has introduced cobordism-like groups based on adjacent relations of connected components of inverse images of regular values and shown a similar theorem.