Eventss

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:
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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
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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
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 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?

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