Computational Logic Seminar

Tuesday, October 22, 2013 2:00 pm Graduate Center, rm, 3209

Speaker: Melvin Fitting Lehman College – CUNY Graduate Center

Title: Justification Logic Semantics: A Little New, but Mostly Old

Link: http://nylogic.org/talks/justification-logic-semantics-a-little-new-but-mostly-old

Possible world semantics was introduced for justification logic in 2005. Initially it was for the Logic of Proofs, but it quickly extended to “nearby” logics, and more slowly to a wider family. Eight years is a long time, and by now people may be generally familiar with the ideas without having gone through any of the details. I will try to remedy that.

Set theory seminar

Friday, October 25, 2013 10:00 am

Speaker: Erin Carmody The CUNY Graduate Center

Title: Killing Inaccessible Cardinals Softly

Link: http://nylogic.org/talks/killing-inaccessible-cardinals-softly

I shall introduce the killing-them-softly phenomenon among large cardinals by showing how it works for inaccessible and Mahlo cardinals. A large cardinal is killed softly whenever, by forcing, one of its large cardinal properties is destroyed while as many as possible weaker large cardinal properties, below this one, are preserved. I shall also explore the various degrees of inaccessibility and show Mahlo cardinals are alpha-hyperbeta-inaccessible and beyond.

Model theory seminar

Friday, October 25, 2013 12:30 pm

Speaker: Alf Dolich The City University of New York

Title: TBA

Link: http://nylogic.org/talks/tba-7

CUNY Logic Workshop

Friday, October 25, 2013 2:00 pm GC 6417

Speaker: Jim Schmerl University of Connecticut

Title: Automorphism Groups of Countable, Recursively Saturated Models of Peano Arithmetic

Link: http://nylogic.org/talks/title-tba-7

It is still unknown whether there are nonisomorphic countable recursively saturated models M and N whose automorphism groups Aut(M) and Aut(N) are isomorphic. I will discuss what has happenednover the last 20 years towards showing that such models do not exist, including some very recent results.

Set theory seminar

Friday, November 1, 2013 10:00 am GC 6417

Speaker: Karel Hrbacek City College of New York, CUNY

Title: Some problems motivated by nonstandard set theory

Link: http://nylogic.org/talks/some-problems-motivated-by-nonstandard-set-theory

Nonstandard set theory enriches the usual set theory by a unary “standardness” predicate. Investigations of its foundations raise a number of questions that can be formulated in ZFC or GB and appear open. I will discuss several such problems concerning elementary embeddings, ultraproducts, ultrafilters and large cardinals.