**Computational Logic Seminar**

** November 13, Time 2:00 – 4:00 PM, GC Room 3309**

Speaker: Wojtek Moczydlowski, Google

Title: Applied higher infinities in impredicative constructive set theories.

Abstract: The Intuitionistic Zermelo Fraenkel set theory IZF was

introduced by Myhill more than 30 years ago, starting investigations

into the world of constructive set theories. I will give an overview

of this area and describe the recent results that apply inaccessible

sets to combine the proof-theoretical benefits of the version with

Replacement with the consistency power of the version with Collection.

Related open questions will be discussed.

**Second Annual Saul Kripke Lecture**

** 4:00-6:00 pm this Tuesday November 13, 2012, at CUNY Graduate Center,**

Rooms C201 and C202

Speaker: John Burgess (John N. Woodhull Professor of Philosophy,

Princeton University)

Title: The Origin of Necessity and the Necessity of Origin

Please visit the Saul Kripke Center’s website for further information,

and to keep up with future events:

http://web.gc.cuny.edu/KripkeCenter/

If you have any questions, feel free to email us atkripkeconference@gc.cuny.edu

**Set Theory Seminar**

** Friday, November 16, 2012, 10:00am GC 6417**

Alexander Rapp

Diamond Plus and the Kurepa Hypothesis

**Model Theory Seminar**

** Friday, November 16, 2012, 12:30pm-1:45pm, GC 6417**

Lynn Scow (UIC)

Generalized Indiscernible Sets, Ehrenfeucht-Mostowski Types, Trees

Abstract: A generalized indiscernible set is a set of parameters $A =

\{a_i : i \in I\}$ where the $a_i$ are finite tuples from a structure

$M$, $I$ is some additional structure, and $A$ satisfies a homogeneity

condition: finite tuples $(a_{i_1}, \ldots, a_{i_n}), (a_{j_1},

\ldots, a_{j_n})$ from $A$ have the same type in $M$, provided the

tuples of their indices, $(i_1,\ldots,i_n), (j_1,\ldots,j_n)$, have

the same quantifier-free type in $I$. Generalized indiscernible sets

were introduced by Shelah in the 70’s and have important applications

in classification theory. In this talk, I will extend the definition

of Ehrenfeucht-Mostowski type (EM-type) from order-indiscernible sets

to generalized indiscernible sets. The EM-type is a means to encode

the important first-order information in $A$, and it can be a useful

way to streamline compactness arguments. In this talk I will survey

the uses of EM-types, and as a consequence, present a new Ramsey class

of trees.

**Logic Workshop**

** Friday, November 16, 2012 2:00 pm GC 6417**

Prof. David Marker (University of Illinois – Chicago)

Integer parts of uncountable real closed fields

Abstract. An integer part of a real closed field is a discretely

ordered subring where every element of the field is within distance

one of an element of the ring. Shepherdson first noticed that integer

parts are models of a weak fragment of arithmetic. Recently, D’Aquino,

Knight and Starchenko studied the real closed fields where the integer

part is a model of Peano Arithmentic and gave a complete

classification in the countable case. We will survey the subject and

examine some phenomena in the uncountable case.

**New York Logic Colloquium**

** November 16, Friday, 4-5:30pm**

CUNY Graduate Center, room C201

Speaker: Johan van Benthem (Professor of Logic, Amsterdam and Stanford

University. http://staff.science.uva.nl/~johan/)

Title: IMPLICIT AND EXPLICIT STANCES IN LOGIC

Abstract: We identify a pervasive contrast in modeling styles in

logic, between ‘implicit’ and ‘explicit’ approaches. Roughly speaking,

the former change the meaning of logical constants and consequence to

accommodate new topics entering the field, while the explicit approach

extends classical logical systems with new vocabulary.

We discuss the contrast in intuitionistic vs. epistemic logic, default

reasoning, logics of questions, information dynamics and games, and

then define the stances more sharply. Many new issues become visible

concerning dualities and merges between the two approaches. Finally,

in philosophical mode, we discuss what the contrast means for an

understanding of logic as a repertoire of natural stances.

References:

Johan van Benthem, 1991, ‘Implicit versus Explicit Views of

Knowledge’, Proceedings TARK. –

2009, ‘The Information in Intuitionistic Logic’, Synthese. –

2011, Logical Dynamics of Information and Interaction, Cambridge

University Press.

THE TALK WILL BE FOLLOWED BY A WINE AND CHEESE RECEPTION.

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