Johan Van Benthem's talk in the Cairo Webinar tomorrow March 15 at 5 pm Cairo time

[jean-yves beziau]

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://en.wikipedia.org/wiki/Johan_van_Benthem_(logician)

 

                           Title: Syntactic Fine-Structure and Generalized Semantics 

                                                           Chair: Tarek Sayed Ahmed

Abstract: While first-order logic is undecidable as a whole, it has a rich and far from

exhausted 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 objects

occurring together in some atomic predicate fact in our models. It is

highly instructive to see how this avoids the patterns of quantification

that are needed to encode undecidable problems inside first-order logic.

At the same time, a quite different perspective is possible. One can also

see 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 the

semantics 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 and

Bounded 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 Logic
UvA, Stanford and Tsinghua University
https://staff.fnwi.uva.nl/j.vanbenthem/

 

Topic: Cairo jamesWebinar
Time: Mar 15, 2022 05:00 PM Cairo

Join Zoom Meeting
https://us02web.zoom.us/j/85778049374?pwd=Q2FwUnQ4bkVZclZ2a0FOY2o3WEY2QT09

Meeting ID: 857 7804 9374
Passcode: 105424

Best wishes, Tarek Sayed Ahmed

On behalf of the organizers, Mohamed Amer, Tarek Sayed Ahmed, Zeinab Mansour, Hala Kamal, Amr Sid Ahmed