2018 Dec 11

Demi Allen (Manchester) A mass transference principle for systems of linear forms with applications to Diophantine approximation

2:15pm to 3:15pm


Ross 70
Abstract: In Diophantine approximation we are often interested in the Lebesgue and Hausdorff measures of certain $\limsup$ sets. In 2006, Beresnevich and Velani proved a remarkable result --- the Mass Transference Principle --- which allows for the transference of Lebesgue measure theoretic statements to Hausdorff measure theoretic statements for $\limsup$ sets arising from sequences of balls in $\mathbb{R}^k$.
2018 Nov 05

NT&AG: Michael Temkin (HUJI), ""Differential forms on Berkovich curves"

3:00pm to 4:00pm


Room 70A, Ross Building, Jerusalem, Israel
This is a continuation of the talk on October 29. After finishing a brief review of basic facts about Berkovich curves, I will associate a reduction datum to differential forms on such curves and explain how a lifting theorem for such data is proved and why it reproves the lifting theorem of [BCGGM].
2018 Oct 31

Logic Seminar - Yatir Halevi

11:00am to 1:00pm


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 Dec 19

Set Theory Seminar - Asaf Karagila (The Morris model)

2:00pm to 3:30pm


Ross 63
Title: The Morris model
Abstract: Douglass Morris was a student of Keisler, and in 1970 he announced the
following result: It is consistent with ZF that for every \alpha, there is a set
A_\alpha which is the countable union of countable sets, and the power set of
A_\alpha can be partitioned into \aleph_\alpha non-empty sets.
The result was never published, and survived only in the form of a short
announcement and an exercise in Jech's "The Axiom of Choice". We go over the
proof of this theorem using modern tools, as well as some of its odd
2018 Nov 06

Jon Aaronson (TAU) On the bounded cohomology of actions of multidimensional groups.

2:15pm to 3:15pm

Although each cocycle for a action of the integers is
specified by the sequence of Birkhoff sums of a function,
it is relatively difficult to specify cocycles for the actions of
multidimensional groups such as $\Bbb Z^2$.
We'll see that if $(X,T)$ is a transitive action of the finitely
generated (countable) group $\Gamma$ by homeomorphism of the polish space $X$,
and $\Bbb B$ is a separable Banach space, there is a cocycle
$F:\Gamma\times X \to\Bbb B$
with each $x\mapsto F(g,x)$ bounded and continuous