Preprint available

[Anders Kock <kock@imf.au.dk>]

My preprint "Projective lines as groupoids with projection structure" is now available at arXiv.

A projection structure on a groupoid consists in giving, for each pair
(A,B) of distinct objects in it, a bijection between the set hom(A,B), and
the set of objects distinct from A and B. Groupoids with such structure
occur naturally in projective geometry over a field.  - The present note
investigates when, conversely, an abstractly given groupoid with projection
structure comes about from a field, constructed out of the groupoid.

http://arxiv.org/abs/1310.5357

Anders



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