# Noon lecture

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On 20.10.2011 at 12:20 in S6, there is the following noon lecture:

# Expansion for 2-complexes

## Anna Gundert

## ETH Zurich

## Abstract

For graphs, there are two ways to define expansion: as a combinatorial or as a spectral property. By the Cheeger inequality these two definitions are very closely connected. In this talk, we will look at generalizations of expansion to 2-dimensional simplicial complexes. Both ways of defining graph expansion can be generalized in a pretty straightforward fashion using basic cohomological notions. But we will see that the close connection of the graph properties does not carry over to the higher dimension.

list of noon lectures ( 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | future lectures)

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