Dear Cheerful Logicians and Friends of Logic, We're returning to a bit of normalcy after a few weeks being inundated with a smorgasbord of workshops and online conferences. This week, there are six events to announce: one on Monday, one on Tuesday, two on Thursday, and two on Friday. Details, as usual, are below.
Supergroup Talk *Speaker: *Isabella McAllister *Title: *Belief revision about logics *Time and Date: *Thursday, November 12 18:00 (GMT-6) *Link: * https://unimelb.zoom.us/j/846890369?pwd=TktZYmlIUGlYOU9ZaXFJcCt0TFJFZz09 *Abstract: *Sometimes philosophers change their beliefs regarding which logical principles are correct. For example, one might come to abandon the law of excluded middle out of constructivist inclinations or reject the material conditional on grounds of irrelevance. Yet mainstream belief revision systems (such as those of the AGM and DDL traditions) cannot handle this kind of belief revision because such systems only model belief revision within logical frameworks, not between them. In my talk, I present an AGM-style belief revision system that can accommodate change in belief about logical principles. I propose various postulates that we should expect to hold of belief revision about logical principles and then show how to construct formal operators that comply with these postulates. Special attention is given to operators that guarantee the non-triviality of new belief sets. Triviality-avoiding revision is not always possible without modifying the non-logical content of one’s beliefs, which generates interesting challenges regarding the relationship between logical and non-logical information. I propose several revision operators that each address these challenges in different ways. Talks by Other Groups: *Logic and Metaphysics Workshop *(CUNY) *Speaker: *Eoin Moore (CUNY) *Title: *Towards a Justification Logic for FDE *Time and Date: *Monday, November 9th, 15:15 (GMT-6) *Link:* https://gc-cuny.zoom.us/j/93538764756?pwd=dzVaUWVnT1BKa0FsWVpSNnJsemFkUT09 *Meeting ID:* 935 3876 4756 *Passcode:* 443837 *Abstract: *In this work-in-progress, I aim to develop a justification logic counterpart to first degree entailment. I produce a logic which is an extension of FDE using justification terms. The results are extended to other paraconsistent logics. *Alophis Seminar *(Università di Cagliari) *Speaker: *Gavin St John *Title: *Decidability for fragments of residuated lattices axiomatized by simple equations *Time and Date: *Tuesday, November 10th, 15:00 CET (8:00 GMT-6) *Link:* https://uva-live.zoom.us/u/keptTFP0t9 *Meeting ID:* 862 3721 6817 *Passcode:* 878074 *Abstract: *The decidability for the universal and (quasi-)equational theories for the varieties of residuated lattices RL extended by equations in the ordered monoid signature {≤, ·, 1} has been a topic richly studied. In particular, commutativity, weakened variants of commutativity, and knotted equations (such as contraction, integrality, and mingle). By the work of van Alten [1999], subvarieties of commutative residuated lattices defined by such equations actually have the finite embeddabillity property and hence are decidable. On the other hand, Horčík [2015] demonstrated the undecidability of the word problem for RL with contraction (and, in fact, equations from a much broader class), which was further bootstrapped by Chvalovský and Horčík [2016] to show that its equational theory is actually undecidable. Following this programme, we investigate decidability questions for subvarieties of RL defined from a broader class of equations, called simple, in the idempotent semiring signature {∨, ·, 1}, as well as compare and contrast the decidability of their various fragments. We show how previous techniques to handle the non-commutative, as well as the commutative, cases can be adapted and improved upon in this broader context and prove new undecidability results for so-called spineless equations. We also show that such subvarieties of residuated lattices are conservative extensions of their corresponding idempotent semirings fragments, which will shed light onto the boundary between decidable and undecidable theories in this context. *Lógicos em Quarentena* *Speaker: *Samuel Gomes da Silva *Title: *On striking, counterintuitive partitions - or: The Axiom of Choice is not to be blamed of anything *Time and Date: *Thursday, November 12 13:00 (GMT-6) *Link: *https://meet.google.com/uwn-tyjb-rbr *Abstract: *One of the more counterintuitive consequences of the Axiom of Choice (perhaps the most celebrated among them all) is the well-known Banach-Tarski Paradox, which is a theorem ({\it not a paradox}) stating that any closed, ``solid"\, ball of the three-dimensional Euclidean space may be decomposed into a finite number of subsets (``pieces", so to say) which, after rearranged using only rigid motions, turn out to form two identical copies of the original ball. Variations of this very same theorem (which heavily relies on the Axiom of Choice) can be spelled out even more strikingly (``one could cut an orange into finite pieces and then reassemble those pieces in order to get a sphere of the size of the Sun"). Of course, the orange pieces referred to would be {\bf non-measurable} -- thus, Banach-Tarski Paradox could be understood as a fancy alternative proof of the well-known fact that the Axiom of Choice easily produces non-measurable subsets of any given Euclidean space. Due to these undeniably counterintuitive aspects, Banach-Tarski Paradox is usually presented as an argument against the acceptance of the Axiom of Choice. In this talk, we will see that the possibly implicit desire of all those anti-Axiom of Choice researchers (which, apparently, would be to discard the Axiom of Choice and then freely work with models of Mathematics on which all subsets of any given Euclidean space are Lebesgue-measurable) would also yeld some highly counterintuitive results regarding partitions of sets -- so, the Axiom of Choice should not be considered the sole culprit when it comes to counterintuitive situations involving partitions ! For instance, we will show in the talk that: if all subsets of the real line are Lebesgue-measurable, then there is a partition of $\mathbb{R}$ into strictly more than $2^{\aleph_0}$ non-empty subsets -- that is, there would be a partition of a set (and not some obscure set -- arguably the most important set of all Mathematics, which is the real line $\mathbb{R}$) into {\bf more pieces than elements} (!!!). Having appeared as a common feature of a number of constructions, we will take the opportunity to discuss the so-called {\it Partition Principle} -- which is an immediate consequence of the Axiom of Choice for which the natural question in the context (``Is this principle, in fact, an equivalent of the Axiom of Choice ?") constitutes itself as one of the oldest (and still open) problems of this kind in the literature. *Logic Webinar@IITK* *Speaker: *Prof. R. Ramanujam (The Institute of Mathematical Sciences (IMSc), Chennai) *Title: *Decidable fragments of first order modal logic *Time and Date: *Friday, November 13th 04:30 GMT-6 *Link: *https://zoom.us/j/98013662384?pwd=RUozRVVlemJGdjBHRmIrODZ0WHhGUT09 *Meeting ID:* 980 1366 2384 *Password:* 601533 *Abstract: *First Order Modal Logic (FOML) is "notoriously" undecidable, in the sense that even very weakly expressive fragments are undecidable. All the understanding of decidable fragments of first order logic and decidable extensions of propositional modal logics gained over 50 years seems to help little. The combination of modalities and quantifiers causes new problems that occur neither in the first-order case nor in the propositional modal case. Despite such discouragement, a small community has battled on, and this century has seen some small steps with positive results on new fragments, like the monodic fragment, bundled fragments, term-modal logics, and such. This line of work has opened up new research vistas with many interesting questions. The talk is an attempt to show you some highlights of this journey. *UConn Logic Group* *Speaker: *Sandra Villata *Title: *Intermediate Grammaticality *Time and Date: *Friday, November 13 09:00 GMT-6 *Link: * https://us02web.zoom.us/j/84038139428?pwd=RS9tNHl2b1l6TGN3NCtnN3hUdDRTZz09 *Meeting ID:* 840 3813 9428 *Passcode: *grammar *Abstract: *Formal theories of grammar and traditional sentence processing models start from the assumption that the grammar is a system of rules. In such a system, only binary outcomes are generated: a sentence is well-formed if it follows the rules of the grammar and ill-formed otherwise. This dichotomous grammatical system faces a critical challenge, namely accounting for the intermediate/gradient modulations observable in experimental measures (e.g., sentences receive gradient acceptability judgments, speakers report a gradient ability to comprehend sentences that deviate from idealized grammatical forms, and various online sentence processing measures yield gradient effects). This challenge is traditionally met by accounting for gradient effects in terms of extra-grammatical factors (e.g., working memory limitations, reanalysis, semantics), which intervene after the syntactic module generates its output. As a test case, in this talk I will focus on a specific kind of violation that is at the core of the linguistic investigation: islands, a family of encapsulated syntactic domains that seem to prohibit the establishment of syntactic dependencies inside of them (Ross 1967). Islands are interesting because, although most linguistic theories treat them as fully ungrammatical and uninterpretable, I will present experimental evidence revealing gradient patterns of acceptability and evidence that some island violations are interpretable. To account for these gradient data, in this talk I explore the consequences of assuming a more flexible rule-based system, where sentential elements can be coerced, under specific circumstances, to play a role that does not fully fit them. In this system, unlike traditional ones, structure formation is forced even under sub-optimal circumstances, which generates semi-grammatical structures in a continuous grammar. 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 If you are part of a member group, are recording talks, and would like the supergroup to host them, then let us know! We'd be happy to help. Yay for logic! p.s. If there seem to be more typos than usual it's because I just burned my finger taking a pie out of the oven.Yes it's delicious. No, you can't have any. Except you, Kim. You can have as much as you want. -- 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/CAMTR99394DsR5Q-y6nPq_Q30ZahbeU4XUjpEMfg%3DY1dWXJu-%2Bg%40mail.gmail.com.
