Logic

The Logic seminar meets on Wednesdays at 11:00.
2018 Nov 21

Logic Seminar - Saharon Shelah

11:00am to 1:00pm

Location: 

Ross 63
קשת איוּם מוֹדל כוֹלל

the spectrum of the existence of a universal model


תמצית/abstract:
קיוּם מוֹדל כולל של תורה בעצמה נתוּנה זו שאלה טבעית בתוֹרת המוֹדלים ובתוֹרת הקבוּצוֹת. נטפל בתנאים מספיקים לאי קיוּם, אין צוֹרך בידיעוֹת מוּקדמוֹת.

The existence of a universal model (of a theory T in a cardinal lambda)  is a natural question in model theory and set theory.  We shall deal with new sufficient conditions for non-existence.
No need of previous knowledge
2018 Dec 26

Logic Seminar - Antongiulio Fornasiero

11:00am to 1:00pm

Location: 

Ross 63

Generic derivations on o-minimal structures
Antongiulio Fornasiero

A derivation on a field K is a map d from K to K such that  d(x + y) = d(x) + d(y) and d(x y) = x d(y) + d(x) y.

Given an o-minimal structure M in a language L, we introduce the notion L-derivation, i.e derivation compatible with L. For example, if M is the field of reals with exponentiation, then we further require that the derivation d satisfies d(exp x) = exp(x) d(x).

2018 Dec 05

Logic Seminar - Omer Ben-Neria

11:00am to 1:00pm

Location: 

Ross 63

Hjorth's theory of turbulence


The purpose of this talk is to survey several results from Hjorth's theory of turbulent polish group actions.
 
 We will start by discussing certain classification problems associated with Borel equivalence relations, and present the notions of Borel reductions and smooth relations, and the E_0 dichotomy theorem of Harrington-Kechris-Louveau.
 
2018 Nov 14

Logic Seminar - Yair Hayut

11:00am to 1:00pm

Location: 

Ross 63

Global Chang's Conjecture

Yair Hayut - (joint with Monroe Eskew)

For $\kappa < \lambda$ infinite cardinals let us consider the following generalization of the Lowenheim-Skolem theorem:
"For every algebra with countably many operations over $\lambda^+$ there is a sub-algebra with order type exactly $\kappa^+$".

We will discuss the consistency and inconsistency of some global versions of this statement and present some open questions. 
2018 Dec 19

Logic Seminar - Udi Hrushovski

11:00am to 1:00pm

Location: 

Ross 63

Model theory and geometry of fields with automorphism


I will review some of the model-theoretic geometry of difference varieties, and some open problems. 
A difference variety is defined by polynomial equations with an additional operator $\si$ interpreted as a field automorphism. 
2019 Jan 02

Logic Seminar - Itaï Ben Yaacov

11:00am to 1:00pm

Location: 

Ross 63
Randomisations, coheir sequences and NSOP1 [Joint with A Chernikov and N Ramsey] Recall that if T is a theory, then its Keisler randomisation, T^R, is the theory of spaces of random variables which take values in a model of T . It was show some time ago that if T has IP (e.g., simple unstable), then T^R has TP2, and in particular not simple. In Eilat I announced the following result [with Chernikov and Ramsey] : A. If T is NSOP1, then its randomisation T^R is NSOP1
2018 Oct 31

Logic Seminar - Yatir Halevi

11:00am to 1:00pm

Location: 

Ross 63

Around the stable and dependent fields conjecture


Abstract: The stable fields conjecture asserts that every infinite stable field is separably closed.
We will talk a bit about the history of this conjecture, its connection to an analogous conjecture on dependent fields and some of their consequences.
Finally, we will end by proving the conjecture for fields of finite dp-rank.
2018 Oct 24

Logic Seminar - Daoud Siniora

11:00am to 1:00pm

Location: 

Ross 63

 Automorphisms of meet-trees


Abstract: A meet-tree is a partial order such that the set of vertices below any vertex is linearly ordered, and for every pair of vertices there is a greatest element smaller than or equal to each of them. I'll talk on a work in progress with Itay Kaplan and Tomasz Rzepecki mainly showing that the universal homogeneous countable meet-tree admits generic automorphisms.

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