2015 Dec 17

# Groups & dynamics: Rene Rühr, Distribution of Shapes of Orthogonal Lattices

10:00am to 11:30am

## Location:

Ross building, Hebrew University of Jerusalem, (Room 70)
To every topological group, one can associate a unique universal
minimal flow (UMF): a flow that maps onto every minimal flow of the
group. For some groups (for example, the locally compact ones), this
flow is not metrizable and does not admit a concrete description.
However, for many "large" Polish groups, the UMF is metrizable, can be
computed, and carries interesting combinatorial information. The talk
will concentrate on some new results that give a characterization of
metrizable UMFs of Polish groups. It is based on two papers, one joint
2016 Nov 03

# Groups and dynamics - Misha Belolipetsky

10:30am to 11:30am

## Location:

Ross 70
Speaker: Misha Belolipetsky
Title: Arithmetic Kleinian groups generated by elements of finite order
Abstract:
We show that up to commensurability there are only finitely many
cocompact arithmetic Kleinian groups generated by rotations. The proof
is based on a generalised Gromov-Guth inequality and bounds for the
hyperbolic and tube volumes of the quotient orbifolds. To estimate the
hyperbolic volume we take advantage of known results towards Lehmer's
problem. The tube volume estimate requires study of triangulations of
2015 Nov 12

# Groups & dynamics: Elon Lindenstrauss (HUJI), "Rigidity of higher rank diagonalizable actions in positive characteristic"

10:00am to 11:00am

## Location:

Ross 70
Title: Rigidity of higher rank diagonalizable actions in positive characteristic
2017 Dec 12

# T&G: Yoel Groman (Columbia), Generation of the Fukaya category of a Lagrangian torus fibration by a section

1:00pm to 2:30pm

## Location:

Room 70A, Ross Building, Jerusalem, Israel
The (wrapped) Fukaya category of a symplectic manifold is a category whose objects are Lagrangian submanifolds and which contains a wealth of information about the symplectic topology. I will discuss the construction of the wrapped Fukaya category for certain completely integrable Hamiltonian systems. These are 2n-dimensional symplectic manifolds carrying a system of n commuting Hamiltonians surjecting onto Euclidean space. This gives rise to a Lagrangian torus fibration with singularities.
2017 May 18

# Basic notions: Ehud de Shalit - The Loxton - van der Poorten conjecture

4:00pm to 5:00pm

Abstract: Adamczewski and Bell proved in the 2013 the Loxton - van der Poorten
conjecture. It says the following. Let f be a Laurent power series (with complex
coefficients) and let \sigma_p be the operator substituting x^p for x in f. Suppose that f satisfies a homogenous polynomial equation in the operator \sigma_p with
coefficients which are rational functions, and a similar equation in the operator \sigma_q where p and q are multiplicatively independent natural numbers. Then f is a rational function.
2016 Mar 16

# Eshnav: Matanya Ben-Artzi - "On the zero set of a function"

## Lecturer:

Matanya Ben-Artzi
6:00pm to 7:00pm

## Location:

Math 2 (Manchester building)
2015 Dec 23

# Eshnav: Dorit Aharonov - "The revolution of quantum information"

Dorit Aharonov
6:00pm to 7:00pm

## Location:

Math 2 (Manchester building)
2017 Dec 13

# Eshnav: Ohad Noy Feldheim - "Lattices, Colorings and Magnets"

6:15pm to 7:15pm

## Location:

Math 2 (Manchester building)
2017 May 25

# Basic notions: Ehud de Shalit - The Loxton - van der Poorten conjecture

4:00pm to 5:00pm

Abstract: Adamczewski and Bell proved in the 2013 the Loxton - van der Poorten
conjecture. It says the following. Let f be a Laurent power series (with complex
coefficients) and let \sigma_p be the operator substituting x^p for x in f. Suppose that f satisfies a homogenous polynomial equation in the operator \sigma_p with
coefficients which are rational functions, and a similar equation in the operator \sigma_q where p and q are multiplicatively independent natural numbers. Then f is a rational function.
2016 Jan 13

# Eshnav: Mike Hochman - "The Isoperimetric Inequality"

Mike Hochman
6:00pm to 7:00pm

## Location:

Math 2 (Manchester building)
2015 Dec 02

# Eshnav: Raz Kupferman - "Geometry and elasticity: from torn nylon to carnivorous plants"

Raz Kupferman
6:00pm to 7:00pm

## Location:

Math 2 (Manchester building)
2015 Nov 11

# Eshnav: Karim Adiprasito (HUJI) "Combinatorial geometry"

6:00pm to 7:00pm

## Location:

Math 2 (Manchester building)
Title: Combinatorial Geometry
Abstract:
Matroids or (combinatorial) geometries are natural abstractions of
the concept of linear and algebraic independence over fields, were defined
by Whitney nearly a century ago. Since then, they have become a crucial tool
in model theory, graph coloring, noncommutative geometty and the study of
characteristic classes. Quite amazingly, it was recently shown that matroids
satisy deep results classically associated to algebraic varieties, something
that was not expected in this generality.
2017 Apr 30

# Combinatorics: Amir Yehudayoff (Technion) TBA

Repeats every week every Sunday until Sun Jun 25 2017 except Sun Apr 30 2017.
11:00am to 1:00pm

11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm
11:00am to 1:00pm

## Location:

Rothberg B221 (CS building)
Speaker: Misha Tyomkyn (TAU)
Title: Lagrangians of hypergraphs and the Frankl-Furedi conjecture
Abstract:
Frankl and Furedi conjectured in 1989 that the maximum Lagrangian of
all r-uniform hypergraphs of given size m is realised by the initial
segment of the colexicographic order. For r=3 this was partially solved
by Talbot, but for r\geq 4 the conjecture was widely open. We verify
the conjecture for all r\geq 4, whenever
$\binom{t-1}{r} \leq m \leq \binom{t}{r}- \gamma_r t^{r-2}$
2016 Jan 14

# Amitsur Algebra: Frauke Bleher (U of Iowa): Holomorphic differentials in positive characteristic

12:00pm to 1:15pm

## Location:

Manchester Building (room 209), Jerusalem, Israel
Title: Holomorphic differentials in positive characteristic
Abstract: This talk is about joint work with Ted Chinburg and Aristides Kontogeorgis.
Let X be a smooth projective curve over an algebraically closed field
k of positive characteristic p. Suppose G is a finite group with non-trivial
2015 Dec 03

# Amitsur Algebra: Boris Plotkin (Hebrew U)

12:00pm to 1:15pm

## Location:

Manchester Building (room 209), Jerusalem, Israel
Title: Algebraic Geometry in an arbitrary variety of algebras and Algebraic Logic
Abstract: I will speak about a system of notions which lead to interesting new problems for groups and algebras as well as to reinterpretation of some old ones.