Dear Cheerful Logicians and Friends of Logic, We are pleased to announce this week's supergroup talk! Details below. There are actually *three* talks by supergroup groups this week, all of them on Thursday.
Before all that, an announcement: A group of academics has proposed a day of work on social justice causes on June 10. More info here <https://www.shutdownstem.com/>. Some supergroup members are participating in this. If you want to join them, email me about it. The hope is to have a 24 hour event, but this will require much more investment from the community than we're currently seeing. Let's see if we can make this happen! *Speaker: *Adam Bjorndahl (Carnegie Melon) *Title: *The Epistemology of Nondeterminism *Time and Date: *Thursday June 11, 8pm GMT-5 *Link: * https://unimelb.zoom.us/j/846890369?pwd=TktZYmlIUGlYOU9ZaXFJcCt0TFJFZz09. *Abstract*: Propositional dynamic logic (PDL) is a framework for reasoning about nondeterministic program executions (or, more generally, nondeterministic actions). In this setting, nondeterminism is taken as a primitive: a program is nondeterministic iff it has multiple possible outcomes. But what does "possible" mean, here? This talk explores an epistemic interpretation: working in an enriched logical setting, we represent nondeterminism as a relationship between a program and an agent deriving from the agent’s (in)ability to adequately measure the dynamics of the program execution. More precisely, using topology and the framework of dynamic topological logic, we show that dynamic topological models can be used to interpret the language of PDL in a manner that captures the intuition above, and moreover that continuous functions in this setting correspond exactly to deterministic processes. We prove that certain axiomatizations of PDL remain sound and complete with respect to corresponding classes of dynamic topological models. We also extend the framework to incorporate knowledge using the machinery of subset space logic, and show that the topological interpretation of public announcements coincides exactly with a natural interpretation of test programs. Finally, we sketch a generalization of the topological paradigm in which the distinction between action and measurement (i.e, between functions and opens) is erased, highlighting some preliminary results in this direction. *Talks by Member Groups* *The Calgary Peripatetic Seminar* Speaker: Brent Odland Title: Peirce’s Triadic Logic: Continuity, Modality, and L Time and Date: Thursday, June 11, 10am GMT-5 Link: email Richard Zach for info. Abstract: In 1909, in his Logic Notebook, Charles Sanders Peirce conducted what appear to be the first experiments with many-valued logic. As these experiments are entirely contained within a handful of pages in his notebook, which were not published or discussed by other authors during his lifetime, little is known about his reasons for conducting this research. By examining and transcribing these pages, and connecting them to his larger body of philosophy, I show how his motivations lie within his views on modality and continuity. *Lógicos em Quarentena (Brazilian Logic Society)* Speaker: Paulo Oliva Title: The Power of Continuations Time and Date: Thursday, June 11, 6pm GMT-5 Link: meet.google.com/jjj-ntym-nnt Abstract: Let us use X, R for types (but you can also think of them as sets or formulas). When working towards a final result r in R, we might need to produce a value x in X. Any function f : X -> R can then be thought of as a "continuation", an oracle that gives us the final result for each value. We call a functional F : (X -> R) -> X as "selection function", these are functionals that operate on continuations in order to produce a value. Example 1: X = some set, R = Bool, so F : (X -> Bool) -> X could be a form of Hilbert's epsilon terms, computing witnesses for given predicates p : X -> Bool. Example 2: X = [0,1], R = Real and F : ([0,1] -> Real) -> [0,1] could be argmax or argmin. Example 3: X = R = some domain D, in this case F : (X -> X) -> X could be the fixed point operator. This talk is about these continuation processing operators, and their use in various areas such as Logic, Domain Theory and Game Theory. *Other Announcements:* The Web School on Logic, Language, and Information is happening July 11-19. More information at https://www.brandeis.edu/nasslli2020/. Of particular interest to our members might be the workshop called Natural Logic Meets Machine Learning; more info at https://typo.uni-konstanz.de/naloma20/. To access the supergroup calendar, please follow this link: https://calendar.google.com/calendar?cid=ZGhoanNoanF1bGhmaG9xam5scDJlc2o0bDhAZ3JvdXAuY2FsZW5kYXIuZ29vZ2xlLmNvbQ To access the member groups joint calendar, please follow this link: https://calendar.google.com/calendar?cid=aG8wNWljaGxkNXI2N2oyMnZvY3BzdmRoMWNAZ3JvdXAuY2FsZW5kYXIuZ29vZ2xlLmNvbQ The latter calendar is currently fairly incomplete---*if you represent a member group and would like your events to appear there, be sure to add them!* Yay for logic! Shay -- 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/CAMTR993chvoJv-bYL7joZOXzv5wvNz0-%3Dyxdz0vw-gVSVJVJuA%40mail.gmail.com.
