Group Actions Seminar: Dani, Gardam

UPDATE: the room is now Carslaw 157, not 173.

There will be a Group Actions Seminar at the University of Sydney next
week, on Monday 24 June.  The speakers will be Pallavi Dani (Louisiana
State) and Giles Gardam (Sydney).  Titles and abstracts are below.

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Date: Monday 24 June

Time: 12 noon

Location: Carslaw 157, University of Sydney

Speaker: Pallavi Dani (Louisiana State University)

Title: Filling invariants: homological vs. homotopical

Abstract: Classical isoperimetric functions give optimal bounds on the
minimal-area fillings of loops by disks.  There are a number of
variations: rather than sticking to loops and disks, one might
consider fillings of spheres by balls, or cycles by chains.  A natural
question then is: for a given space are these functions the same?  Or
are there spaces in which a particular type of filling (say filling
cycles by chains) is more efficient than other types? What if the
space is quasi-isometric to a finitely presented group?  I will talk
about recent work with A. Abrams, N. Brady and R. Young which
addresses this question.

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Date: Monday 24 June

Time: 3pm

Location: Carslaw 157, University of Sydney

Speaker: Giles Gardam (University of Sydney)

Title: Graphs and triangles of groups

Abstract: Bass-Serre theory studies group actions on trees, unifying
two combinatorial constructions from group theory, namely free product
with amalgamation and the HNN extension, which are understood as
special cases of graphs of groups. This talk will give an introduction
to Bass-Serre theory up to and including its so-called fundamental
theorem. We will also introduce Gersten and Stallings’ notion of
non-positively curved triangles of groups, as a first step towards the
more general theory of complexes of groups.

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