> > Dear all, > > > > > > > > > > > > > > > > > > > > > *It is my pleasure to cordially invite you to attend the next talk in the > Cairo logic Webinar (via Zoom--free of charge) scheduled for tomorrow at 5 > pm Cairo time (15th of March 2022): Johan > Van Benthem (Amsterdam- Stanford-Tsinghua) > https://staff.science.uva.nl/j.van benthem/ > <https://staff.science.uva.nl/j.vanbenthem/> > https://en.wikipedia.org/wiki/Johan_van_Benthem_(logician) > <https://en.wikipedia.org/wiki/Johan_van_Benthem_(logician)> > Title: Syntactic Fine-Structure and Generalized Semantics > Chair: Tarek Sayed > AhmedAbstract: While first-order logic is undecidable as a whole, it has a > rich and far fromexhausted syntactic fine-structure of decidable > sublanguages. This talk will focus on one of these, the Guarded Fragment, > introduced by Andreka, van Benthem & Nemeti in 1998, and still the subject > of ongoing investigations.'Guarding' means restricting quantifiers to range > only over objectsoccurring together in some atomic predicate fact in our > models. It ishighly instructive to see how this avoids the patterns of > quantificationthat are needed to encode undecidable problems inside > first-order logic.At the same time, a quite different perspective is > possible. One can alsosee the Guarded Fragment as closely related to > generalizing the standard semantics for the complete language of > first-order logic so as to relax the mathematical assumptions that underlie > [and explain] the undecidability. This is done by allowing models having > only restricted sets of admissible assignments, much like the `teams' > of modern logics of dependence and independence. Many decidable > logics live on this generalized semantics, including CRS from the earlier > algebraic logic tradition and its recently introduced dependence logic > extension LFD. The two perspectives of syntactic fine-structure and > generalizing thesemantics of first-order logic are closely connected by a > number of [both old and new] translation results. This raises the > intriguing question whether in logic, somewhat paradoxically, contracting > [to a sublanguage] and expanding [to a richer class of models] are two > sides of the same coin. The talk will explain all of the above in more > technical detail, and end with some general points for discussion.Ref. (1) > H. Andreka, J. van Benthem & I. Nemeti, 'Modal Languages andBounded > Fragments of Predicate Logic', Journal of Philosophical Logic, 1998. (2) H. > Andreka, J. van Benthem, N. Bezhanishvili & I. Nemeti, 'Changing a > Semantics: Opportunism or Courage?', in M. Manzano et al., eds., Volume in > Honor of Leon Henkin, 2014. (3) A. Baltag & J. van Benthem, 'A Simple Logic > of Functional Dependence', Journal of Philosophical Logic, > 2021. --------------------------------------------Johan van Benthem, > Professor of LogicUvA, Stanford and Tsinghua > Universityhttps://staff.fnwi.uva.nl/j.vanbenthem/ > <https://staff.fnwi.uva.nl/j.vanbenthem/> Topic: Cairo jamesWebinarTime: > Mar 15, 2022 05:00 PM CairoJoin Zoom > Meetinghttps://us02web.zoom.us/j/85778049374?pwd=Q2FwUnQ4bkVZclZ2a0FOY2o3WEY2QT09 > <https://us02web.zoom.us/j/85778049374?pwd=Q2FwUnQ4bkVZclZ2a0FOY2o3WEY2QT09>Meeting > ID: 857 7804 9374Passcode: 105424* > > Best wishes, Tarek Sayed Ahmed > > On behalf of the organizers, Mohamed Amer, Tarek Sayed Ahmed, Zeinab > Mansour, Hala Kamal, Amr Sid Ahmed > >
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