On Thu, Mar 23, 2006 at 12:17:05PM +0000, Robin Houston wrote:

I recently proved that [finite] products (or coproducts) in a compact closed category are necessarily biproducts, and I'm wondering whether this is a known theorem.

Since a couple of you have been asking about this, I thought I should post a quick followup message. I had several private replies, almost all of them asking to see the proof. None of my respondents knew of an existing proof. A preliminary paper, describing the proof, in far more detail than most of the people on this list would need, is available from http://www.arxiv.org/abs/math.CT/0604542 (If any of you have any comments on it, I'd be interested in hearing them.) Yours, Robin