# 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.

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