The Logic seminar meets on Wednesdays at 11:00.

2019
Jan
16

The Logic seminar meets on Wednesdays at 11:00.

2019
Jan
16

2019
Jan
16

11:00am to 1:00pm

Ross 63

(M. Magidor, joint work with I. Farah)

2018
Nov
21

11:00am to 1:00pm

Ross 63

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

11:00am to 1:00pm

Ross 63

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
Nov
28

11:00am to 1:00pm

Ross 63

2018
Dec
05

11:00am to 1:00pm

Ross 63

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

11:00am to 1:00pm

Ross 63

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

11:00am to 1:00pm

Ross 63

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.

2018
Dec
12

2019
Jan
02

11:00am to 1:00pm

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
Nov
07

2018
Oct
31

11:00am to 1:00pm

Ross 63

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

11:00am to 1:00pm

Ross 63

2018
Jul
11

11:00am to 1:00pm

Ross 70A

We develop a correspondence between the study of Borel equivalence relations induced by closed subgroups of $S_\infty$, and the study of symmetric models of set theory without choice, and apply it to prove a conjecture of Hjorth-Kechris-Louveau (1998).

2018
Jun
19

4:00pm to 6:00pm

Math 209

Abstract: Let V be an irreducible algebraic subvariety of C^n X C^n of
dimension n.
If Schanuel Conjecture holds, under some natural conditions on V, we
show that, if V is defined over the rationals, there exists a in C^n
such that (a, exp(a)) is a generic point of V.