Dear Cheerful Logicians and Friends of Logic, Before getting to the week's events, a note: there is a workshop being hosted by the University of St. Andrews this week that is likely to be of interest to some of you. The topic is "Theories of Paradox in the Middle Ages". It will run via Zoom on October 21, 22, and 23. Details can be found at the following link: https://www.st-andrews.ac.uk/arche/event/paradoxes-in-the-middle-ages/.
There are six events to announce this week: one each on Monday and Wednesday, and two each on Thursday and Friday. Supergroup Talk *Speaker: *Ana Claudia Golzio (UNICAMP) *Title: *Swap structures semantics for some logics of formal inconsistency *Time and Date: *Friday, October 23 09:00 GMT-5 *Link: * https://ksu.zoom.us/j/99677150172?pwd=MFFBcXlDdVpuRjRXaGVRU1ZwUmdOdz09 *Meeting ID:* 996 7715 0172 *Passcode:* structures *Abstract: * Multialgebras (or hyperalgebras) are algebras which at least one of the operations (called multioperations) returns a subset instead of a single element of the domain. Multialgebras have been very much studied in the literature and in the realm of Logic, they were considered by Avron and his collaborators, under the name of non-deterministic matrices (or Nmatrices), as a useful semantics tool for characterizing some logics of formal inconsistency (LFIs). In particular, these logics of formal inconsistency are not algebraizable by any method, including Blok and Pigozzi general theory. Carnielli and Coniglio introduced a semantics of swap structures for LFIs, which are Nmatrices constructed over triples in a Boolean algebra, generalizing Avron’s non-deterministic matrices. In this work we develop the first steps towards an algebraic theory of swap structures for LFIs. The logic mbC is the weakest system in the hierarchy of LFIs and the system QmbC is the extension of mbC to first-order language. The goal of this talk is to present the first steps towards a theory of non-deterministic algebraization of logics by swap structures. Specifically, a formal study of swap structures for logics of formal inconsistency is developed, by adapting concepts of universal algebra to multialgebras in a suitable way and we introduce also an algebraic semantics for QmbC. From the algebraic point of view these structures enable us to obtain properties of first-order logic QmbC and in the proof of the Soundness Theorem we can see interesting particularities of the first-order swap structures, especially with respect to the Substitution Lemma. This study opens new avenues for dealing with non-algebraizable logics through by the more general methodology of multialgebraic semantics. Talks by Other Groups: *Logic and Metaphysics Workshop* (CUNY) *Speaker: *Michael Glanzberg (Rutgers) *Title: *Models, Model Theory, and Modeling *Time and Date: *Monday, October 19th 15:15 GMT-5 *Link: * https://gc-cuny.zoom.us/j/92056358765?pwd=ZjAwcnNvOUNwcXJaTCtqMGdjdXFhdz09 *Meeting ID: *920 5635 8765 *Passcode: *281885 *Abstract: *In this paper, I shall return to the relations between logic and semantics of natural language. My main goal is to advance a proposal about what that relation is. Logic as used in the study of natural language—an empirical discipline—functions much like specific kinds of scientific models. Particularly, I shall suggest, logics can function like analogical models. More provocatively, I shall also suggest they can function like model organisms often do in the biological sciences, providing a kind of controlled environment for observations. My focus here will be on a wide family of logics that are based on model theory, so in the end, these claims apply equally to model theory itself. Along the way towards arguing for my thesis about models in science, I shall also try to clarify the role of model theory in logic. At least, I shall suggest, it can play distinct roles in each domain. It can offer something like scientific models when it comes to empirical applications, while at the same time furthering conceptual analysis of a basic notion of logic. *IU Logic Seminar* *Speaker: *Siddharth Bhaskar (University of Copenhagen) *Title: *Traversal-Invariant Definability and Logarithmic Space *Time and Date: *Wednesday, October 21st 13:00 GMT-5 *Link: * https://iu.zoom.us/j/95326399432?pwd=VmVUWGxHeG5KQjEzQVozb3pCRHJVZz09 *Meeting ID: *953 2639 9432 *Passcode: *Smullyan *Abstract: *Presentation invariance is the phenomenon in which a quantity is defined in terms of some additional structure (or "presentation") but is then shown to be independent of it. Common examples are the dimension of a vector space (defined as the cardinality of basis), or Euler characteristic of a surface (defined in terms of a triangulation). Presentation invariance is a prominent theme in descriptive complexity theory, which deals with finite structures encoded as strings, but insists that queries must be independent of the encoding. In this talk, I will give characterizations of deterministic and nondeterministic logarithmic space in terms of first-order queries in the language of graphs, with invariant usage of a traversal, a particular linear ordering of the vertices of a graph. This is the first such characterization of these classes that I know of which does not have an obvious mechanism for "computation," such as a fixed-point operator; rather, all the computation is "hidden" in the presentation itself. I then describe how to extend traversal-invariant definability to classes of infinite structures. To do this, we need to bypass the Craig interpolation theorem, which is commonly thought of as an obstacle to presentation-invariant definability over arbitrary structures. I conclude with some ideas of how to investigate traversal-invariant definability from the perspective of abstract model theory. This work is joint with Steven Lindell and Scott Weinstein. *GROLOG (Groningen Logic Group)* *Speaker: *Prof. dr. Allard Tamminga (Universität Greifswald) *Title: *Expressivity Results for Deontic Logics of Collective Agency *Time and Date: *Thursday, October 22nd 08:15 GMT-5 *Link: * https://us02web.zoom.us/j/87071955060?pwd=VktPQkppTEk2d08ycEExbTh2Q3FJdz09 *Meeting ID: *870 7195 5060 *Passcode: *561643 *Abstract: *We use a deontic logic of collective agency to study reducibility questions about collective agency and collective obligations. The logic that is at the basis of our study is a multi-modal logic in the tradition of stit ('sees to it that') logics of agency. Our full formal language has constants for collective and individual deontic admissibility, modalities for collective and individual agency, and modalities for collective and individual obligations. We classify its twenty-seven sublanguages in terms of their expressive power. This classification enables us to investigate reducibility relations between collective deontic admissibility, collective agency, and collective obligations, on the one hand, and individual deontic admissibility, individual agency, and individual obligations, on the other. (Joint work with Hein Duijf and Frederik Van De Putte) *Lógicos em Quarentena* *Speaker: *Marcos Silva (UFPE) *Title: *Revision of Logic, Reflexive Equilibrium and Normative Bidirectionality *Time and Date: *Thursday, October 22nd 14:00 GMT-5 *Link: *https://meet.google.com/jtw-gsuu-umt *Abstract: *How could we rationally justify our logical principles, if the very possibility of rational justification presupposes them? To what extent is it possible to revise something as fundamental as logical principles? How could we justify a set of basic principles of logic as the correct one without circularity or infinite regress? In our paper, we will explore a pragmatist and normative approach to the epistemic problem of justification and revision of the most basic logical rules. We defend that logic is a science analogous to normative disciplines as defended by Prawitz (1978) and Peregrin e Svoboda (2017). This pragmatist method defends the revision of logic based on the notion of reflexive equilibrium in relation to our general theoretical considerations and local instances as particular inferences, revising any of these elements, whenever necessary, in order to obtain an acceptable coherence among them. We will develop the notion of normative bidirectionality and argue that what we call upward normative pressure adequately expresses the dynamical aspect in the revision of logical principles. *UConn Logic Group* *Speaker: *Tyler Markkanen (Springfield College) *Title: *Computing Perfect Matchings in Graphs *Time and Date: *Friday, October 23rd 13:00 GMT-5 *Link: * https://us02web.zoom.us/j/82415300828?pwd=YVEyUGhqRExEL0h0TjFhQnYxcEtCQT09 *Meeting ID: *824 1530 0828 *Passcode: *8q8aAk *Abstract: *A matching of a graph is any set of edges in which no two edges share a vertex. Steffens gave a necessary and sufficient condition for countable graphs to have a perfect matching (i.e., a matching that covers all vertices). We analyze the strength of Stephens’ theorem from the viewpoint of computability theory and reverse mathematics. By first restricting to certain kinds of graphs (e.g., graphs with bounded degree and locally finite graphs), we classify some weaker versions of Stephens’ theorem. We then analyze Stephens’ corollary on the existence of maximal matchings, which is critical to his proof of the main theorem. Finally, using methods of Aharoni, Magidor, and Shore, we give a partial result that helps hone in on the computational strength of Stephens’ theorem. Joint with Stephen Flood, Matthew Jura, and Oscar Levin. 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! -- Você está recebendo esta mensagem porque se inscreveu no grupo "LOGICA-L" dos Grupos do Google. 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