Published online by Cambridge University Press: 09 November 2020
Let $\Omega $ be a connected open set in the plane and
$\gamma : [0,1] \to \overline {\Omega }$ a path such that
$\gamma ((0,1)) \subset \Omega $. We show that the path
$\gamma $ can be “pulled tight” to a unique shortest path which is homotopic to
$\gamma $, via a homotopy h with endpoints fixed whose intermediate paths
$h_t$, for
$t \in [0,1)$, satisfy
$h_t((0,1)) \subset \Omega $. We prove this result even in the case when there is no path of finite Euclidean length homotopic to
$\gamma $ under such a homotopy. For this purpose, we offer three other natural, equivalent notions of a “shortest” path. This work generalizes previous results for simply connected domains with simple closed curve boundaries.
L.C.H. was partially supported by NSERC grant RGPIN 435518. L.G.O. was partially supported by NSF-DMS-1807558. E.D.T. was partially supported by NSERC grant OGP-0005616.