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সায়ন্তন রায় (Nov 04 2020 at 06:58):The following event organised by Indian Institute of Technology, Kanpur may be of interest to some people.
Speaker: Prof Friedrich Wehrung (Universite de Caen, France)
Title: Purity and freshness (in categorial model theory)
Time and Date: Friday, November 6th 04:30 GMT-6
Link: https://zoom.us/j/91420898789?pwd=WnRqWGhYRVEvd0pwZXpkaEd6WDB1dz09
Meeting ID: 914 2089 8789
Passcode: 874519
Abstract: The aim of this talk is to introduce the basic concepts of a technique enabling to prove that certain naturally defined classes of structures are ``intractable’’ in the sense that they cannot be described as classes of models of any infinitely formula (or more generally, of any class of formulas, for any infinite cardinal ).The main idea is that for any suitably ``continuous’’ functor , from the category of all subsets of some set and one-to-one maps between those, to a category of models, all large enough morphisms in the range of are elementary embeddings with respect to large infinitary languages.
This yields the concept of anti-elementarity, which entails intractability.
In particular, this applies to classes such as (1) the class of all posets of finitely generated ideals in rings, (2) the class of all ordered groups of unit-regular rings, (3) the class of all lattices of principal -ideals of abelian lattice-ordered groups (yields a negative answer to the so-called MV-spectrum problem).
Peter Arndt (Nov 06 2020 at 13:28):Oh man, I have done very similar work - I would love to see this, but I will not have time then. Will it be recorded?
সায়ন্তন রায় (Nov 06 2020 at 13:44):Yep. It is recorded. They will make the video available in this page (it's supposed to stay there for two weeks).
Peter Arndt (Nov 06 2020 at 14:13):Cool, thanks!
সায়ন্তন রায় (Nov 22 2020 at 12:54):The following event organised by Indian Institute of Technology, Kanpur may be of interest to some people.
Speaker: Prof. Jiří Rosický (Masaryk University, Brno, Czech Republic)
Title: From first order logic to accessible categories
Time and Date: Friday, November 27th 05:30 GMT-6
Link: https://zoom.us/j/98905165937?pwd=ZVNERnBLNGhkRUcrY1R1TU1hbXFlUT09
Meeting ID: 989 0516 5937
Passcode: 425391
Abstract: We will introduce accessible categories and explain their relations to model theory, in particular to abstract elementary classes of Shelah. We explain how it liberates model theory from a concrete presentation of structures. In particular, internal ranks replace cardinalities of underlying sets. We show that it makes it possible to extend Shelah's Categoricity Conjecture beyond abstract elementary classes.
সায়ন্তন রায় (Feb 09 2021 at 04:16):The following event organised by Indian Institute of Technology, Kanpur may be of interest to some people. (Yes, it's back again.)
Speaker: Dr. Purbita Jana, (Indian Institute of Technology, Kanpur)
Title: Logic, Algebra, Topology, Topological System and their interconnection
Time and Date: Friday, February 12th, 07:30 GMT-6
Link: https://zoom.us/j/93200125020?pwd=bHh3eVJMbGFNSExPVnVpckprSm82Zz09
Meeting ID: 932 0012 5020
Passcode: 470773
Abstract: In this talk I will focus on the connection among logic, algebra, topology and topological system. Firstly, I will discuss the notion of topological system and its connection with geometric logic, frame and topology following the work by Steve Vickers. Then I will talk about our recent work on intuitionistic topological systems and its connection with intuitionistic logic, Heyting algebra and Esakia space.
সায়ন্তন রায় (Feb 12 2021 at 13:29):A reminder, the talk is in less than 10 minutes.
সায়ন্তন রায় (Apr 02 2021 at 07:10):Time: April 2, 2021 07:00 PM (GMT+5:30)
Join Zoom Meeting: https://zoom.us/j/96332744622?pwd=MjlqbFZ1RXBVRWV3bEhLVzhBT0VBdz09
Meeting ID: 963 3274 4622
Passcode: 368978
Speaker: Dr. Sam van Gool, IRIF, Université de Paris, France.
Title: What is an existentially closed Heyting algebra and what does it have to do with automata?
Abstract: Logical systems of deduction often resemble algebraic systems of equations. The simplest and original case of this is the correspondence between Boole's propositional logic and algebras over the 2-element field. When one changes the logical deduction system, the algebraic structures become less simple, and more interesting: Heyting algebras, modal algebras, and generalizations of such.
The aim of our work is to use model theory to better understand these algebraic structures coming from logic. Model completeness plays a central role in this study. In traditional model-theoretic algebra, model completeness provides the correct abstraction of the concept of an algebraically closed field. We show that model completeness also has an important role to play in logical algebra.
In particular, we will discuss two cases of model completeness in logical algebra: linear temporal logic and intuitionistic logic. In the former, automata on infinite words are the technical ingredient that leads to model completeness. In the latter, model completeness is shown to be closely related to a certain interpolation property of the logic, originally established by Pitts.
সায়ন্তন রায় (Apr 19 2021 at 06:25):Time: April 23, 2021 07:00 PM (GMT+5:30)
Join Zoom Meeting: https://zoom.us/j/98614756239?pwd=OCtYSzV1c2lxWVgyZmVDTEpRRkxHZz09
Meeting ID: 986 1475 6239
Passcode: 813434
Speaker: Prof. Rohit Parikh, City University of New York, U.S.A.
Title: The Sorites paradox, Fuzzy Logic, and Wittgenstein's Language Games
Abstract: We look at the history of research on vagueness and the Sorites paradox. That search has been largely unsuccessful and the existing solutions are not quite adequate. But following Wittgenstein we show that the notion of a successful language game works.
Language games involving words like "small" or "red" can be successful and people can use these words to cooperate with others. And yet, ultimately these words do not have a meaning in the sense of a tight semantics. It is just that most of the time these games work. It works to say, the light is green and we can go," even though the color word green" does not actually have a semantics.
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