On the space of ends of countable groups
Institución: CNRS ENS Lyon
Tipo de Evento: Investigación, Formación de Recursos Humanos
Cuándo |
08/02/2019 de 13:00 a 15:00 |
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Dónde | Salón de seminarios "Graciela Salicrup" |
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The notion of ends of group is possibly the earliest geometric property of
finitely generated groups, introduced by Freudenthal in 1930. It was
readily established that every such group has 0, 1, 2, or infinitely many
ends, and in the latter case is a Cantor space. Stallings in the late 60s
characterized infinitely-ended finitely generated groups in terms of
group splittings. In 1950, Specker found a natural way to define the space
of ends for arbitrary groups, and proved that for an infinitely generated
group, the space of ends is either a singleton or is infinite. We study
the topology of this space. We prove that it has no isolated point, and
that for some infinitely generated countable groups it is a Cantor space,
while for some other cases it is non-metrizable.