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On the Intersection Power Graph of a Finite Group
Given a group G, the intersection power graph of G, denoted by , is the graph with vertex set G and two distinct vertices x and y are adjacent in if there exists a non-identity element such that x^m=z=y^n, for some , i.e. in if and is adjacent to all other vertices, where is the identity element of the group G. Here we show that the graph is complete if and only if either G is cyclic p-group or G is a generalized quaternion group. Furthermore, is Eulerian if and only if |G| is odd. We characterize all abelian groups and also all non-abelian p-groups G, for which is dominatable. Beside, we determine the automorphism group of the graph , when
Spectral rigidity of automorphic orbits in free groups
It is well-known that a point in the (unprojectivized)
Culler-Vogtmann Outer space is uniquely determined by its
\emph{translation length function} . A subset of a
free group is called \emph{spectrally rigid} if, whenever
are such that for every then in . By
contrast to the similar questions for the Teichm\"uller space, it is known that
for there does not exist a finite spectrally rigid subset of .
In this paper we prove that for if is a subgroup
that projects to an infinite normal subgroup in then the -orbit
of an arbitrary nontrivial element is spectrally rigid. We also
establish a similar statement for , provided that is not
conjugate to a power of .
We also include an appended corrigendum which gives a corrected proof of
Lemma 5.1 about the existence of a fully irreducible element in an infinite
normal subgroup of of . Our original proof of Lemma 5.1 relied on a
subgroup classification result of Handel-Mosher, originally stated by
Handel-Mosher for arbitrary subgroups . After our paper was
published, it turned out that the proof of the Handel-Mosher subgroup
classification theorem needs the assumption that be finitely generated. The
corrigendum provides an alternative proof of Lemma~5.1 which uses the
corrected, finitely generated, version of the Handel-Mosher theorem and relies
on the 0-acylindricity of the action of on the free factor complex
(due to Bestvina-Mann-Reynolds). A proof of 0-acylindricity is included in the
corrigendum.Comment: Included a corrigendum which gives a corrected proof of Lemma 5.1
about the existence of a fully irreducible element in an infinite normal
subgroup of of Out(F_N). Note that, because of the arXiv rules, the
corrigendum and the original article are amalgamated into a single pdf file,
with the corrigendum appearing first, followed by the main body of the
original articl
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