2018
May
22

# Events & Seminars

2016
Dec
19

# Special logic seminar - Elad Levi "Algebraic regularity lemma for hypergraphs"

10:00am to 12:00pm

## Location:

Sprinzak 101

Speaker: Elad Levi
Algebraic regularity lemma for hypergraphs
Abstract: Szemer´edi’s Regularity Lemma is a fundamental tool in graph theory. It states that for every large enough graph, the set of vertices has a partition A1,..,Ak, such that for almost every two subsets Ai,Aj the induced bipartite graph on (Ai,Aj) is regular, i.e. similar to a random bipartite graph up to a given error.

2018
May
09

# Logic Seminar - Immanuel Benporat - "Arbault sets"

11:00am to 1:00pm

## Location:

Ross 63

Arbault sets (briefly, A-sets) were first introduced by Jean Arbault in the context of Fourier analysis. One of his major results concerning these sets,asserts that the union of an A-set with a countable set is again an A-set. The next obvious step is to ask what happens if we replace the word "countable" by א_1. Apparently, an א_1 version of Arbault's theorem is independent of ZFC. The aim of this talk would be to give a proof (as detailed as possible) of this independence result. The main ingredients of the proof are infinite combinatorics and some very basic Fourier analysis.

2017
Mar
15

# Logic seminar - Rizos Sklinos, "Non-equational stable groups"

4:00pm to 6:00pm

## Location:

Ross 70

Non-equational stable groups.
Speaker: Rizos Sklinos
Abstract: The notion of equationality has been introduced by Srour and further
developed by Pillay-Srour. It is best understood intuitively as a notion
of Noetherianity on instances of first-order formulas. A first-order
theory is equational when every first-order formula is equivalent to a
boolean combination of equations.
Equationality implies stability and for many years these two notions were
identified, as only an "artificial" example of Hrushovski (a tweaked
pseudo-space) was witnessing otherwise. Recently Sela proved that the

2017
Nov
01

# Logic Seminar - Immanuel BenPorat - "Cardinal conditions for strong Fubini theorems"

11:00am to 1:00pm

## Location:

Math209

This talk will be largely based on a paper by Joseph Shipman with the same title. We will discuss some variations of Fubini type theorems. The focus will be on what is known as "strong Fubini type theorems". Apparently these versions were proved to be independent of ZFC,and our main aim will be to sketch a proof of this result. We will assume basic knowledge in measure theory. Aside from that, the material is rather self contained.

2018
May
23

# Logic Seminar - Alejandro Poveda Ruzafa - "A Magidor-like study of $C^{(n)}$-cardinals"

11:00am to 1:00pm

## Location:

Ross 63

The notion of reflection plays a central role in modern Set Theory since the descovering of the well-known Lévy and Montague \textit{Reflection principle}. For any $n\in\omega$, let $C^{(n)}$ denote the class of all ordinals $\kappa$ which correctly interprets the $\Sigma_n$-statements of the universe, with parametes in $V_\kappa$.

2017
Dec
27

# Logic Seminar - Omer Ben-Neria - "Singular Stationarity and Set Theoretic Generalizations of Algebras"

11:00am to 1:00pm

## Location:

Ross 63

Abstract: The set theoretic generalizations of algebras have been
introduced in the 1960s to give a set theoretic interpretation of usual
algebraic structures. The shift in perspective from algebra to set
theory is that in set theory the focus is on the collection of possible
algebras and sub-algebras on specific cardinals rather than on
particular algebraic structures. The study of collections of algebras
and sub-algebras has generated many well-known problems in combinatorial
set theory (e.g., Chang’s conjecture and the existence of small singular
Jonsson cardinals).

2018
Mar
21

# Logic Seminar - Jorge Julián Prieto Jara - "Differentially closed fields and quasiminimality"

11:00am to 1:00pm

## Location:

Ross 63

Zilber introduced quasi-minimal classes to generalize the model theory of pseudo exponential
fields. They are equipped with a pregeometry operator and satisfy interesting properties such
as having only countable or co-countable definable sets. Differentially closed fields of
characteristic 0, rich examples of a \omega-stable structures, are good candidates to be
quasiminimal. The difficulty is that a differential equation may have uncountably many
solutions, and thus violate the countable closure requirement of quasiminimal structures.

2017
Apr
19

# Logic seminar- Shimon Garti, "Forcing axioms and saturated ideals"

4:00pm to 6:00pm

## Location:

Ross 70

Abstract: Paul Larson proved that under Martin's axiom and large continuum there are no Laver ideals over aleph_1. He asked about weakly Laver ideals under some forcing axiom.
We shall address two issues:
1. Under Martin's axiom and the continuum is above aleph_2, there are no weakly Laver ideals over aleph_1..
2. Under Baumgartner's axiom, the parallel of Larson's theorem holds for ideals over aleph_2.

2017
Jul
10

# Special logic seminar - Noa Lavi, "Independent chapters in dependent theories"

11:00am to 1:00pm

## Location:

Ross 70

This talk is about three published papers of mine that form my phd. In the first two chapters I focus in the model theory of real closed fields and in the third one I take one step back and investigate in greater genearility dependent theories.
The results are the following:
1. Boundedness criterion for rational functions over generalized semi-algebraic sets in real closed fields.
2. Positivity criterion for polynomials over generalized semi-algebraic sets in real closed valued fields.

2018
Jun
20

# Logic Seminar - Daniel Palacin - "On definable Bohr compactifications of ultraproducts of finite groups"

11:00am to 1:00pm

## Location:

Ross 63

Abstract: In this talk I will discuss some suitable definable Bohr compactification of an ultraproduct of finite groups, and relate it to ultra quasirandom groups.

2017
Dec
06

# Logic Seminar - Daoud Siniora - "Automorphism groups of homogeneous structures"

11:00am to 1:00pm

## Location:

Math 209

A special class among the countably infinite relational structures is the class of homogeneous structures. These are the structures where every finite partial isomorphism extends to a total automorphism. A countable set, the ordered rationals, and the random graph are all homogeneous.

2018
Jan
24

# Logic Seminar - Vadim Kulikov - Borel Reducibility in Generalised Descriptive Set Theory"

11:00am to 1:00pm

## Location:

Ross 63

I will review some recent results in the Borel reducibility on uncountable cardinals of the Helsinki logic group.
Borel reducibility on the generalised Baire space \kappa^\kappa for uncountable \kappa is defined analogously to that for \kappa=\omega. One of the corollaries of this work is that under some mild cardinality assumptions on kappa, if T1 is classifiable and T2 is unstable or superstable with OTOP, then the ISOM(T1) is continuously reducible ISOM(T2) and ISOM(T2) is not Borel reducible to ISOM(T1).

2017
May
24

# Logic seminar - Katrin Tent, "Ample geometries of finite Morley rank"

4:00pm to 6:00pm

## Location:

Ross 70

Abstract: I will explain the model theoretic notion of ampleness and present the geometric context of recent constructions.

2017
Apr
24

# Logic seminar

Repeats every week every Monday until Sun May 21 2017 except Mon May 01 2017.

12:00pm to 2:00pm12:00pm to 2:00pm

12:00pm to 2:00pm

## Location:

Ross 63

We will take a close look at the first few steps of the construction of the Bristol model, which is a model intermediate to L[c], for a Cohen real c, satisfying V
eq L(x) for all x.