Dear all,
please note there will be no LIRa this Friday, but you are invited to attend the SMART Lecture presented by Vincent F. Hendricks, with an introduction by Sonja Smets.
The next LIRa session will be on Monday with Greg Restall.
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Date: Friday, March 3rd 2017, 16:00-17:30
Title: Bubbles Go Bust
Speaker: Vincent F. Hendricks (University of Copenhagen)
Venue: Room F0.01, Oudemanhuispoort 4-6, 1012 CN Amsterdam
Abstract: Besides champagne, bubbles are typically associated with situations in finance in which assets trade at prices far exceeding their fundamental value. That was the way of the Dutch tulip bulb frenzy in the 1630s and the subprime crises in 2008. The market overheated, bubbles went bust with catastrophic consequences. But bubbles are not confined to the world of finance. In fact one may today speak of information bubbles, status bubbles, bullying bubbles, political bubbles, news bubbles, even science bubbles. Vincent F. Hendricks, Professor of Formal Philosophy, and Director of the Center for Information and Bubble Studies at the University of Copenhagen, walks you through bubble studies using a wide range of entertaining, thought-provoking and disconcerting examples from the world of finance, social media, politics, populism, fake news and post-factual democracy. On the way he punctures some of the most inflated tendencies of today's public debate especially on social media.
Link: http://smartcs.uva.nl/shared-content/events/events/events/2016-2017/vincent-...
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Date and Time: Monday, March 6th 2017, 16:00-18:00
Title: Proof Terms for Classical Derivations.
Speaker: Greg Restall (University of Melbourne)
Venue: KdVI Seminar Room F3.20, Science Park 107.
Abstract. I give an account of proof terms for derivations in a sequent calculus for classical propositional logic. The term for a derivation δ of a sequent Σ≻Δ encodes how the premises Σ and conclusions Δ are related in δ. This encoding is many–to–one in the sense that different derivations can have the same proof term, since different derivations may be different ways of representing the same underlying connection between premises and conclusions. However, not all proof terms for a sequent Σ≻Δ are the same. There may be different ways to connect those premises and conclusions. Proof terms can be simplified in a process corresponding to the elimination of cut inferences in sequent derivations. However, unlike cut elimination in the sequent calculus, each proof term has a unique normal form (from which all cuts have been eliminated) and it is straightforward to show that term reduction is strongly normalising — every reduction process terminates in that unique normal form. Further- more, proof terms are invariants for sequent derivations in a strong sense — two derivations δ1 and δ2 have the same proof term if and only if some permutation of derivation steps sends δ1 to δ2 (given a relatively natural class of permutations of derivations in the sequent calculus). Since not every derivation of a sequent can be permuted into every other derivation of that sequent, proof terms provide a non-trivial account of the identity of proofs, independent of the syntactic representation of those proofs.
Link: http://consequently.org/writing/proof-terms-for-classical-derivations/
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Hope to see you there!
The LIRa team