A celebrated theorem of Anosov
states that for any continuous self-map f : M → M of a nilmanifold M, the Nielsen
number equals the Lefschetz number in absolute value. Anosov also showed that this
result does not hold for infranilmanifolds, even in the simplest possible situation of
flat manifolds with cyclic holonomy group.
Nevertheless, in this paper we extend Anosov’s theorem to infranilmanifolds with
cyclic holonomy group, provided a certain easily checked condition on the holonomy
representation is satisfied.
In the case of flat manifolds with cyclic holonomy group this condition is
necessary and sufficient. In the general case of all infranilmanifolds with cyclic
holonomy group, we provide an example which shows that this condition is no longer
necessary.
We also prove that for any nonorientable flat manifold Anosov’s theorem is not
true, but again the same example shows that this is not valid in general for
nonorientable infranilmanifolds.
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