Dear Cheerful Logicians and Friends of Logic, There are four talks to announce this week: one each on Monday, Wednesday, Thursday, and Friday. All the details below can be found on either the main calendar or the member groups calendar on the supergroup website, which you can find at https://sites.google.com/view/logicsupergroup/.
Details about all of these talks are also found below. Supergroup Talk Speaker: Michał Godziszewski (MCMP) Title: Modal Quantifiers, Potential Infinity, and Yablo sequences Time and Date: Friday, September 18 0900 GMT-5 Link: https://ksu.zoom.us/j/98927095498?pwd=L0czT2Y3WENFbXBJUjVMVXNON1cydz09 *Meeting ID:* 989 2709 5498 *Passcode:* munich Abstract: When properly arithmetized, Yablo's paradox results in a set of formulas which (with local disquotation in the background) turns out to be consistent, but $\omega$-inconsistent. Adding either uniform disquotation or the $\omega$-rule results in inconsistency. Since the paradox involves an infinite sequence of sentences, one might think that it doesn't arise in finitary contexts. We study whether it does. It turns out that the issue depends on how the finitistic approach is formalized. On one of them, proposed by M. Mostowski, all the paradoxical sentences simply fail to hold. This happens at a price: the underlying finitistic arithmetic itself is $\omega$-inconsistent. Finally, when studied in the context of a finitistic approach which preserves the truth of standard arithmetic, the paradox strikes back --- it does so with double force, for now the inconsistency can be obtained without the use of uniform disquotation or the $\omega$-rule. This is joint work with Rafał Urbaniak from the University of Gdańsk. Talks by Other Groups: *NYU Logic and Metaphysics Seminar* *Speaker: *Chris Scambler (NYU *Title: *Cantor's Theorem, Modalized *Time and Date: *Monday, September 14 15:15 GMT-5 *Link: * https://gc-cuny.zoom.us/j/96869491549?pwd=MXpTNWlSSFRSdU5aVFF6dTg1RXdoZz09 *Meeting ID: *968 6949 1549 *Passcode: *602751 *Abstract: *I will present a modal axiom system for set theory that (I claim) reconciles mathematics after Cantor with the idea there is only one size of infinity. I’ll begin with some philosophical background on Cantor’s proof and its relation to Russell’s paradox. I’ll then show how techniques developed to treat Russell’s paradox in modal set theory can be generalized to produce set theories consistent with the idea that there’s only one size of infinity. *Helsinki Logic Seminar* Speaker: Phokion Kolaitis (UC Santa Cruz and IBM Research - Almaden) Title: The Query Containment Problem: Set Semantics vs. Bag Semantics Time and Date: Wednesday, September 16 10:00 GMT-5 Link: https://helsinki.zoom.us/j/63880559261?pwd=dzViaTA3U1lkQ2YvM2NOZVNacVovdz09 Abstract: Query containment is a fundamental algorithmic task in database query processing and optimization. Under set semantics, the query-containment problem for conjunctive queries has long been known to be NP-complete. SQL queries, however, are typically evaluated under bag semantics and return multisets (bags) as answers, since duplicates are not eliminated unless explicitly specified. The exact complexity of the query-containment problem for conjunctive queries under bag semantics has been an outstanding problem for more than twenty-five years. To this date, it is not even known whether conjunctive-query containment under bag semantics is decidable. The aim of this talk is to present a comprehensive overview of results about the query-containment problem for conjunctive queries and their variants under bag semantics, including recent results that reveal tight connections between this problem and open problems in information theory. *Lógicos em Quarentena* Speaker: Damian Szmuc (IIF-SADAF/CONICET) Title: The fragment of Classical Logic that respects the Variable-Sharing Principle Time and Date: Thursday, September 17 14:00 GMT-5 Link: https://meet.google.com/qjd-qfiq-vof Abstract: We provide a logical p-matrix semantics and a Gentzen-style sequent calculus for the first-degree entailments valid in R. Epstein's Relatedness Logic, which incidentally coincides with the fragment of Classical Logic that respects the Variable Sharing Principle. We achieve the former by introducing a logical p-matrix closely related to that inducing paracomplete weak Kleene logic, and the latter by presenting a calculus where the left and right rules for negation are subject to linguistic constraints. Other Notes and Announcements: - *The Logic Supergroup has a YouTube channel!* Recordings of almost all talks are available at https://www.youtube.com/channel/UCqOAS8SHP-5nGjYEE2FE6xw Yay for logic! -- Você está recebendo esta mensagem porque se inscreveu no grupo "LOGICA-L" dos Grupos do Google. Para cancelar inscrição nesse grupo e parar de receber e-mails dele, envie um e-mail para [email protected]. Para ver esta discussão na web, acesse https://groups.google.com/a/dimap.ufrn.br/d/msgid/logica-l/CAMTR993-jWsDXY81FVP3OZyOrbgKpK1ws-0yeBW%3DteL1K-B%3DCQ%40mail.gmail.com.
