
Pfaffian functions, introduced by Khovanskii in late 70s, are
analytic functions satisfying triangular systems of first order
partial differential equations with polynomial coefficients.
They include for instance algebraic and elementary transcendental functions
in the appropriate domains, iterated exponentials, and {\em fewnomials}.
A simple example, due to Osgood, shows that the first order theory of
reals expanded by restricted Pfaffian functions does not admit quantifier
elimination.
On the other hand, Gabrielov and Wilkie proved (nonconstructively)
that this theory is model complete, i.e., {\em one type} of quantifiers can be
eliminated.
The talk will explain some ideas behind recent algorithms for this {\em quantifier
simplification} which are based on effective cylindrical cell decompositions
of subPfaffian sets.
Complexities of these algorithms are essentially the same as the ones which
existed for a particular case of semialgebraic sets.
© 20022003 Kurt Gödel Society, Norbert Preining. 
20030709
 