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Published online by Cambridge University Press: 21 July 2015
Let $f$ be an orientation and area preserving diffeomorphism of an oriented surface
$M$ with an isolated degenerate fixed point
$z_{0}$ with Lefschetz index one. Le Roux conjectured that
$z_{0}$ is accumulated by periodic orbits. In this paper, we will approach Le Roux’s conjecture by proving that if
$f$ is isotopic to the identity by an isotopy fixing
$z_{0}$ and if the area of
$M$ is finite, then
$z_{0}$ is accumulated not only by periodic points, but also by periodic orbits in the measure sense. More precisely, the Dirac measure at
$z_{0}$ is the limit in the weak-star topology of a sequence of invariant probability measures supported on periodic orbits. Our proof is purely topological. It works for homeomorphisms and is related to the notion of local rotation set.