Events & Seminars

2018 May 08

Dynamics Seminar: Yinon Spinka (TAU): Finitary codings of Markov random fields

2:15pm to 4:15pm

Location: 

Ross 70
Let X be a stationary Z^d-process. We say that X is a factor of an i.i.d. process if there is a (deterministic and translation-invariant) way to construct a realization of X from i.i.d. variables associated to the sites of Z^d. That is, if there is an i.i.d. process Y and a measurable map F from the underlying space of Y to that of X, which commutes with translations of Z^d and satisfies that F(Y)=X in distribution. Such a factor is called finitary if, in order to determine the value of X at a given site, one only needs to look at a finite (but random) region of Y.
2018 Apr 12

Special talk: Yonatan Harpaz (Paris 13) - "Small extensions in algebra and topology"

Lecturer: 

Yonatan Harpaz (Paris 13)
1:15pm to 2:15pm

Location: 

Ross 70
Abstract: In this talk, we will discuss the notion of small extensions in its various incarnations, from torsors under abelian groups to square-zero extensions of algebras. We will then focus on the somewhat less familiar case of small extensions of ∞-categories. Our main goal is to make this abstract concept concrete and intuitive through a variety of examples. In particular, we will advocate the point of view that small extensions of  ∞-categories offer a unifying perspective in understanding many constructions appearing in obstruction, classification, and deformation theoretic problems
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.
2016 Dec 27

Special logic seminar - Itaï BEN YAACOV, "Baby version of the asymptotic volume estimate"

10:00am to 12:00pm

Location: 

Shprinzak 102
I'll show how the Vandermonde determinant identity allows us to estimate the volume of certain spaces of polynomials in one variable (or rather, of homogeneous polynomials in two variables), as the degree goes to infinity. I'll explain what this is good for in the context of globally valued fields, and, given time constraints, may give some indications on the approach for the "real inequality" in higher projective dimension.
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 Nov 08

Logic Seminar- Itai Ben Yaacov - "Reconstruction for non-aleph0-categorical theories?"

11:00am to 1:00pm

Location: 

Math 209
It is a familiar fact (sometimes attributed to Ahlbrandt-Ziegler, though it is possibly older) that two aleph0-categorical theories are bi-interpretable if and only if their countable models have isomorphic topological isomorphism groups. Conversely, groups arising in this manner can be given an abstract characterisation, and a countable model of the theory (up to bi-interpretation, of course) can be reconstructed.
2018 Jan 10

Logic Seminar - Alex Lubotzky - "First order rigidity of high-rank arithmetic groups"

11:00am to 1:00pm

Location: 

Ross 63
The family of high rank arithmetic groups is a class of groups playing an important role in various areas of mathematics. It includes SL(n,Z), for n>2 , SL(n, Z[1/p] ) for n>1, their finite index subgroups and many more. A number of remarkable results about them have been proven including; Mostow rigidity, Margulis Super rigidity and the Quasi-isometric rigidity.

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