On the 3x3x3-Lemma
 
 
Description: 

The idea of a short exact sequence of short exact sequences naturally leads to the 3x3-Lemma. What happens when this process is repeated? The aim of this talk is to explain the connection between the concept of a 3-fold extension, short exact sequences of 3x3-diagrams, and a congruence distributivity condition which in the context of an exact Mal'tsev category leads to a denormalised 3x3x3-Lemma. In the context of a semi-abelian category, we ask the question, when a triple of subobjects of a given object induces a 3x3x3-diagram: the answer is non-trivial even in the abelian case.

(Joint work with Cyrille Sandry Simeu)

Date:  2021-01-19
Start Time:   16:00
Speaker:  Tim Van der Linden (UCLouvain, Belgium)
Institution:  Université catholique de Louvain, Louvain-la-Neuve
Research Groups: -Algebra, Logic and Topology
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