• 2018 Oct 21

# Feldenkrais and Mathematics

Sun, 21/10/2018 (All day) to Tue, 23/10/2018 (All day)

## Location:

Israel Institute for Advanced Studies, The Hebrew University of Jerusalem
• 2018 Oct 21

# Kazhdan seminar: Tomer Schlank "The Nonabelian Chabauty Method"

Repeats every week every Sunday, 14 times .
12:00pm to 2:00pm

## Location:

Ross 70A
Abstract: The Chabauty method is a remarkable tool which employs p-adic analitic methods (in particular Colman integration.) To study rational points on curves. However the method can be applied only when the genus of the curve in question is larger than its Mordell-Weil rank. Kim developed a sophisticated "nonableian" generalisation. We shall present the classical methid, and give an approachable introduction to Kim's method. I'm basically going to follow http://math.mit.edu/nt/old/stage_s18.html
• 2018 Oct 21

# Kazhdan seminar: Karim Adiprasito "Positivity in combinatorics and beyond"

Repeats every week every Sunday, 14 times .
3:00pm to 5:00pm

## Location:

Ross 70A
Abstract: I will discuss applications of algebraic results to combinatorics, focusing in particular on Lefschetz theorem, Decomposition theorem and Hodge Riemann relations. Secondly, I will discuss proving these results combinatorially, using a technique by McMullen and extended by de Cataldo and Migliorini. Finally, I will discuss Lefschetz type theorems beyond positivity. Recommended prerequisites: basic commutative algebra
• 2018 Oct 22

# Combinatorics: Spencer Backman, HU, "Cone valuations, Gram's relation, and flag-angles"

11:00am to 1:00pm

## Location:

Rothberg CS building, room B500, Safra campus, Givat Ram
Speaker: Spencer Backman, HU Title: Cone valuations, Gram's relation, and flag-angles
• 2018 Oct 22

# NT & AG Lunch: Jasmin Matz "Modular forms"

1:00pm to 2:00pm

## Location:

Faculty lounge, Math building
Abstract: Modular forms are historically the first example of automorphic forms, and are still studied today as they have many applications. In this talk I want to introduce modular forms, give some examples, and, if time permits, explain the connection to elliptic curves, objects we already met in the first lecture.
• 2018 Oct 23

# Dynamics Lunch: Amir Algom "On \alpha \beta sets."

12:00pm to 1:00pm

## Location:

Manchester faculty club
Let $\alpha, \beta$ be elements of infinite order in the circle group. A closed set K in the circle is called an \alpha \beta set if for every x\in K either x+\alpha \in K or x+\beta \in K. In 1979 Katznelson proved that there exist non-dense \alpha \beta sets, and that there exist \alpha \beta sets of arbitrarily small Hausdorff dimension. We shall discuss this result, and a more recent result of Feng and Xiong, showing that the lower box dimension of every \alpha \beta set is at least 1/2.
• 2018 Oct 23

# Dynamics Seminar: Nishant Chandgotia (HUJI). Some universal models for Z^d actions

2:15pm to 3:15pm

## Location:

Ross 70
Krieger’s generator theorem shows that any free invertible ergodic measure preserving action (Y,\mu, S) can be modelled by A^Z (equipped with the shift action) provided the natural entropy constraint is satisfied; we call such systems (here it is A^Z) universal. Along with Tom Meyerovitch, we establish general specification like conditions under which Z^d-dynamical systems are universal. These conditions are general enough to prove that 1) A self-homeomorphism with almost weak specification on a compact metric space (answering a question by Quas and Soo)
• 2018 Oct 24

# Analysis Seminar: Boaz Slomka (WIS) "An improved bound for Hadwiger’s covering problem via thin shell inequalities for the convolution square"

12:00pm to 1:00pm

## Location:

Room 70, Ross building
Title: An improved bound for Hadwiger’s covering problem via thin shell inequalities for the convolution square. Abstract: A long-standing open problem, known as Hadwiger’s covering problem, asks what is the smallest natural number N(n) such that every convex body in {\mathbb R}^n can be covered by a union of the interiors of at most N(n) of its translates. Despite continuous efforts, the best-known general upper bound for this number remain as it was more than half a decade ago, and is of the order of \binom{2n}{n}n\ln n.
• 2018 Oct 24

# Logic Seminar - Daoud Siniora

7:00pm to 9:00pm

## Location:

Ross 63

Automorphisms of meet-trees

Abstract: A meet-tree is a partial order such that the set of vertices below any vertex is linearly ordered, and for every pair of vertices there is a greatest element smaller than or equal to each of them. I'll talk on a work in progress with Itay Kaplan and Tomasz Rzepecki mainly showing that the universal homogeneous countable meet-tree admits generic automorphisms.
• 2018 Oct 25

# Colloquium: Karim Adiprasito (HUJI) - Combinatorics, topology and the standard conjectures beyond positivity

2:30pm to 3:30pm

## Location:

Manchester Building (Hall 2), Hebrew University Jerusalem
Consider a simplicial complex that allows for an embedding into R^d. How many faces of dimension d/2 or higher can it have? How dense can they be? This basic question goes back to Descartes. Using it and other rather fundamental combinatorial problems, I will motivate and introduce a version of Grothendieck's "standard conjectures" beyond positivity (which will be explored in detail in the Sunday Seminar). All notions used will be explained in the talk (I will make an effort to be very elementary)