[FOM] Shipman's field question
urquhart at cs.toronto.edu
Thu Oct 26 09:59:58 EDT 2006
On Wed, 25 Oct 2006, Thomas Forster wrote:
> I recently spent an evening with a friend who had an Executive Toy in the
> form of ball-and-stick gadgets for making toy models of chemicals. It
> occurred to me that the question of whether or not these structures are
> rigid ( = not deformable) is not obviously trivial. Is this something on
> which the (decidable) first-order theory of the reals as an ordered field
> has anything amusing to say...?
The right framework for rigidity questions seems to be linear algebra
and its generalizations. In particular, there is a well developed
theory of combinatorial rigidity in the framework of matroid theory.
As far as I know, Tarski's decision procedure is not useful in this
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