# Homotopy properties of smooth functions on the M\"obius band

## TL;DR

This paper investigates the homotopy properties of smooth functions on the Möbius band, specifically computing the isotopy classes of diffeomorphisms preserving such functions under certain conditions.

## Contribution

It provides explicit calculations of the group of isotopy classes of diffeomorphisms preserving Morse functions on the Möbius band, extending to non-orientable surfaces.

## Key findings

- Computed the group of isotopy classes of diffeomorphisms preserving Morse functions on the Möbius band.
- Extended results to certain classes of functions on non-orientable surfaces.
- Established conditions under which the computations hold for functions with specific germ properties.

## Abstract

Let $B$ be a M\"obius band and $f:B \to \mathbb{R}$ be a Morse map taking a constant value on $\partial B$, and $\mathcal{S}(f,\partial B)$ be the group of diffeomorphisms $h$ of $B$ fixed on $\partial B$ and preserving $f$ in the sense that $f\circ h = f$. Under certain assumptions on $f$ we compute the group $\pi_0\mathcal{S}(f,\partial B)$ of isotopy classes of such diffeomorphisms. In fact, those computations hold for functions $f:B\to\mathbb{R}$ whose germs at critical points are smoothly equivalent to homogeneous polynomials $\mathbb{R}^2\to\mathbb{R}$ without multiple factors. Together with previous results of the second author this allows to compute similar groups for certain classes of smooth functions $f:N\to\mathbb{R}$ on non-orientable surfaces $N$.