Generalizations of Reeb spaces of special generic maps and applications to a problem of lifts of smooth maps

Abstract

A Reeb space is defined as the space of all the connected components of inverse images of a smooth map, which is a fundamental tool in studying smooth manifolds using generic smooth maps whose codimensions are not positive such as Morse functions, their higher dimensional versions including fold maps and general stable maps. A special generic map is a fold map and a generalization of Morse functions with just 2 singular points on homotopy spheres and the Reeb space is a compact manifold whose dimension is equal to that of the target manifold and which can be immersed into the target manifold. In this paper, we generalize a quotient map onto a Reeb space of a special generic map. We define a map onto a polyhedron locally a quotient map induced from a special generic map. Moreover, we take advantage of the generalized maps to construct lifts of Morse functions of a certain class; the composition of the lift and the canonical projection is the original funciton. It is an answer of an explicit problem in the studies of lifts of smooth maps, or maps such that the compositions of the found maps and the canonical projections are original maps, which are fundamental and important in the studies of smooth maps and applications to algebraic and differential topology of manifolds.