2018 Jan 15

# Combinatorics Seminar: Leonardo Martinez

11:00am to 12:30pm

2017 Mar 27

# Combinatorics: Micha Sharir (TAU) "Eliminating depth cycles for lines and triangles, with applications to bounding incidences"

11:00am to 1:00pm

## Location:

Rothberg B220 (CS bldg)
Speaker: Micha Sharir (Tel Aviv University)
Title: Eliminating depth cycles for lines and triangles, with applications to bounding incidences
Abstract:
---------
The talk presents three related results.
We first consider the problem of eliminating all depth cycles in a set of n lines in 3-space.
For two lines l_1, l_2 in 3-space (in general position), we say that l_1 lies below l_2 if the
unique vertical line that meets both lines meets l_1 at a point below the point where it meets l_2.
2016 Dec 19

# Combinatorics: Lukas Kühne (U. Bonn) "Heavy hyperplanes in multiarrangements and their freeness"

11:00am to 1:00pm

## Location:

Rothberg B220 (CS)
Speaker: Lukas Kühne (University of Bonn)
Title: Heavy hyperplanes in multiarrangements and their freeness
Abstract:
One of the central topics among the theory of hyperplane arrangements is their freeness. Terao's conjecture tries to link the freeness with the combinatorics of an arrangement. One of the few categories of arrangements which satisfy this conjecture consists of 3-dimensional arrangements with an unbalanced Ziegler restriction. This means that the arrangement contains a lot of hyperplanes intersecting in one single line
2017 Mar 06

# Combinatorics: Zilin Jiang (Technion) "Relations between Tverberg points and central points"

11:00am to 1:00pm

## Location:

Rothberg B220 (CS)
Speaker: Zilin Jiang (Technion)
Title: Relations between Tverberg points and central points
Abstract:
Given 3n lines in general position in the plane, it is always possible to partition them into n triples of lines so that all the triangles, formed by the triples, share a common point. This result is known back in 1988 by J.P. Roudneff. Strangely, in higher dimensions, it is only proved by Roman Karasev for n that is a prime power.
2016 Feb 29

# Combinatorics

Repeats every week every Monday until Mon Jun 13 2016 .
10:30am to 12:30pm

10:30am to 12:30pm
10:30am to 12:30pm
10:30am to 12:30pm
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10:30am to 12:30pm
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10:30am to 12:30pm
10:30am to 12:30pm
10:30am to 12:30pm
10:30am to 12:30pm
10:30am to 12:30pm

## Location:

B220 Rothberg (CS and Engineering building)
NOTE THE SPECIAL TIME: 11:00--12:30
Speaker: Eyal Ackerman, University of Haifa at Oranim
Title: Coloring points with respect to squares
Abstract:
Is there an absolute constant $m$ such that any finite planar point set can be 2-colored such that every axis-parallel square that contains at least $m$ points contains points of both colors? I will discuss this problem and related ones.
2017 Nov 20

# Combinatorics seminar:Sria Louis

11:00am to 12:30pm

## Location:

IIAS Room 130
Speaker 1: Sria Louis
Title: Asymptotically Almost Every 2r-regular Graph has an Internal Partition
Abstract: An internal partition of a graph is a partitioning of the vertex set into two parts such that for every vertex, at least half of its neighbors are on its side. It is easy to notice that such a partition doesn't always exist (e.g. - cliques), though, both the existence and finding of such a partition - are open problems.
2016 Dec 05

# Combinatorics: Klim Efremenko (TAU) " Testing Equality in Communication Graphs"

11:00am to 1:00pm

## Location:

B220 Rothberg (CS)
Speaker: Klim Efremenko (TAU)
Title: Testing Equality in Communication Graphs
Abstract:
Let G=(V,E) be a connected undirected graph with k vertices. Suppose
that on each vertex of the graph there is a player having an n-bit
string. Each player is allowed to communicate with its neighbors
according to a (static) agreed communication protocol and the players
must decide, deterministically, if their inputs are all equal. What
is the minimum possible total number of bits transmitted in a protocol
2018 Mar 26

# Combinatorics seminar: Chaim Even Zohar (UC Davis) "Patterns in Random Permutations"

11:00am to 12:30pm

## Location:

IIAS, room 130, Feldman Building, Givat Ram
2017 Jan 23

# Combinatorics: Elchanan Mossel (MIT) "Lower Bounds on Same-Set Inner Product in Correlated Spaces"

11:00am to 1:00pm

## Location:

Rothberg B220 (CS bldg)
Speaker: Elchanan Mossel (MIT)
Title: Lower Bounds on Same-Set Inner Product in Correlated Spaces
Abstract: Suppose we pick X uniformly from {0,1,2}^n and Y is picked by letting each Y(i) = X(i) or
X(i) + 1 mod 3 with probability 0.5 each independently.
Is it true that for every set S with |S| > c 2^n it holds that the probability that both X and Y are in S is at least g(c) > 0, where g does not depend on the dimension n?
Similar questions were asked before in different contexts. For example,
2017 Dec 25

# Combinatorics Seminar: Yuval Peres

11:00am to 12:30pm

## Location:

Room 130 at the IIAS
Title: Trace reconstruction for the deletion channel
2016 Nov 21

# Combinatorics: David Ellis (Queen Mary) "Some applications of the $p$-biased measure to Erd\H{o}s-Ko-Rado type problems"

11:00am to 1:00pm

## Location:

B220 Rothberg (CS)
Speaker: David Ellis, Queen Mary
Title: Some applications of the $p$-biased measure to Erd\H{o}s-Ko-Rado type problems
Abstract:
2017 May 29

# Combinatorics: Dmitry Faifman (U Toronto) "The integral geometry of indefinite signature"

11:00am to 1:00pm

## Location:

Rothberg B220 (CS bldg)
Speaker: Dmitry Faifman (U Toronto)
Title: The integral geometry of indefinite signature.
2017 Mar 02

# Amitsur Algebra: Lev Glebsky, " Almost Congruence Extension Property for subgroups of free groups"

12:00pm to 1:00pm

## Location:

Manchester Building, Room 209
Title: Almost Congruence Extension Property for subgroups of free groups.
Abstract.
The talk essentially based on: https://arxiv.org/abs/1606.02345
Let G be a group and H every normal subgroup N of H is an intersection of some normal subgroup of G with H. The CEP appears in group theory in different context.
The following question seems to be very difficult:
Which finitely generated subgroup of a free group has CEP?
2017 Feb 09

# Amitsur Algebra: Evan DeCorte, "The spectral method for geometric colouring problems"

12:00pm to 1:00pm

## Location:

Manchester Building, Room 209
Title: The spectral method for geometric colouring problems