### Klein 2-Geometry VIII

#### Posted by David Corfield

As John said:

categorification is a very broad project, like a huge tidal wave hitting the whole length of the shoreline. If certain parts don’t advance as fast as others, it’s really no big deal.

We’ve been trying to ride other parts of the wave of late, so there’s not much to report on last month’s events.

Something we did find is that the Poincaré 2-group is a full sub-2-group of the general linear 2-group of a skeletal Baez-Crans real 2-vector space of dimension (4, 1), i.e., with $R^4$ worth of objects and $R$ worth of morphisms from an object to itself.

There was also some speculation about the possibility and/or value of a composition of 2-groups, which prompted some exposition on $K$-enriched profunctors.

Posted at December 1, 2006 9:44 AM UTC