| Seminários de Lógica Matemática 
 5 de Fevereiro 2009, 18h00
 The model-theoretic proof of the witnessing theorem of bounded arithmetic (an   exposition)
 Complexo Interdisciplinar,   Sala B3-01
 
 KERRY OJAKIAN (SQIG-IT)
         Abstract: 
 I will introduce the   framework of Bounded Arithmetic (BA), a subtheory of Peano Arithmetic which   corresponds to "polynomial-time reasoning." One of the key facts about BA is the   polynomial-time witnessing theorem, which says that the provably- total   functions of BA are exactly the polynomial-time functions. The original proof of   this fact was proof theoretic. Subsequently there were model theoretic proofs,   one from Wilkie (written up by Hajek and Pudlak) and one from Zambella. I will   give an exposition of Zambella ´s proof. I will only assume knowledge of basic   logic, basic model theory, and very basic computational complexity theory.
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