Fiber-connected, indefinite Morse 2-functions on connected n-manifolds.

Gay, David T; Kirby, Robion C · Proc Natl Acad Sci U S A · 2011

basic_science · Level V

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Abstract

We discuss generic smooth maps from smooth manifolds to smooth surfaces, which we call "Morse 2-functions," and homotopies between such maps. The two central issues are to keep the fibers connected, in which case the Morse 2-function is "fiber-connected," and to avoid local extrema over one-dimensional submanifolds of the range, in which case the Morse 2-function is "indefinite." This is foundational work for the long-range goal of defining smooth invariants from Morse 2-functions using tools analogous to classical Morse homology and Cerf theory.