2019
Jun
03

# Combinatorics - back to back:

11:00am to 1:00pm

## Location:

CS Rothberg bldg, room B-500, Safra campus

First talk:
Speaker: Madeleine Weinstein (Berkeley)
Title: Voronoi Cells of Varieties
Abstract:

2019
Jun
03

11:00am to 1:00pm

CS Rothberg bldg, room B-500, Safra campus

First talk:
Speaker: Madeleine Weinstein (Berkeley)
Title: Voronoi Cells of Varieties
Abstract:

2019
Jun
24

11:00am to 1:00pm

2019
May
13

11:00am to 1:00pm

CS bldg, room B-500, Safra campus

Speaker: Shira Zerbib (U. Michigan, Iowa State University)
Title: Envy-free division of a cake without the “hungry players" assumption
Abstract:
The fair division theorem due to Stromquist (1980) ensures that under some conditions it is possible to divide a rectangular cake into n pieces and assign one piece to each of n players such that no player strictly prefers a piece that has not been assigned to him.

2019
May
06

11:00am to 1:00pm

CS building, room B-500, Safra campus

Speaker: Omri Ben Eliezer, TAU
Title: Finding patterns in permutations
Abstract:
For two permutations sigma and pi, we say that sigma contains a copy of
pi, if there is a subset (not necessarily consecutive) of elements in sigma,
whose relative order is the same as in pi. For example, if pi = (1,2,3),
then a copy of pi in sigma amounts to an increasing subsequence in sigma
of length 3.
As shown by Guillemot and Marx, a copy of a constant length pi can be
found in sigma in linear time. However, how quickly can one find such a

2019
Jun
10

11:00am to 1:00pm

CS bldg, room B-500, Safra campus

Speaker: Eyal Karni (BIU)
Title: Combinatorial high dimensional expanders
Abstract:
An eps-expander is a graph G=(V,E) in which every set of vertices X where |X|<=|V|/2 satisfies |E(X,X^c)|>=eps*|X| . There are many edges that "go out" from any relevant set.

2019
May
27

11:00am to 1:00pm

CS Rothberg bldg, room B-500, Safra campus

Speaker: Uri Rabinovich (U. Haifa)
Title: SOME EXTREMAL PROBLEMS ABOUT SIMPLICIAL COMPLEXES
Abstract:
We shall discuss the following three issues:
* The existence of Hamiltonian d-cycles, i.e., simple d-cycles containing a spanning d-hypertree of a complete d-complex K_n^d;
* The existence of a distribution D over spanning d-hypertrees T of K_n^d, so that for ANY
(d-1)-cycle C there, the expected size of the d-filling of C with respect to a random T from D is Omega(n^d);
* The existence of f(k,d) such that any d-simplex of rank r with > f(k,d)*r d-faces contains

2019
Mar
25

11:00am to 1:00pm

CS B-500, Safra campus

Speaker: Roy Meshulam (Technion)
Title: Topology and combinatorics of the complex of flags
Abstract:

2019
May
20

2019
Apr
15

11:00am to 1:00pm

CS B-500, Safra campus

Speaker: Eyal Karni, BIU
Title: Combinatorial high dimensional expanders
Abstract:
An eps-expander is a graph G=(V,E) in which every set of vertices X where |X|<=|V|/2 satisfies |E(X,X^c)|>=eps*|X| . There are many edges that "go out" from any relevant set.

2019
Apr
01

11:00am to 1:00pm

CS B-500, Safra campus

Speaker: Raphy Yuster, U. Haifa
Title: On some Ramsey type problems in tournaments
Abstract:
I will talk about several Ramsey type problems in tournaments guaranteeing the existence of subgraphs with certain chromatic properties.
Here are two such problems which attracted some attention recently:
1. Let g(n) be the smallest integer such that every tournament with more than g(n) vertices has an *acyclic subgraph* with chromatic number larger than n.
It is straightforward that Omega(n) <= g(n) <= n^2. An improvement of both bounds is presented.

2019
Mar
18

11:00am to 1:00pm

CS B-500, Safra campus

Speaker: Arindam Banerjee, RMVERI
Title: Castelnuovo-Mumford Regularity, Combinatorics and Edge Ideals.
Abstract:

2019
Jun
17

11:00am to 1:00pm

U. Haifa

From Raphy Yuster: On Monday 17 June, 2019 we will hold a one day mini conference in memory of
Professor Yossi Zaks
(see attached poster or updated information in
http://sciences.haifa.ac.il/math/wp/?page_id=1382 )
Speakers:
Noga Alon (Princeton and Tel Aviv University)
Gil Kalai (Hebrew University)
Nati Linial (Hebrew University)
Rom Pinchasi (Technion)
Schedule:
10:00-10:15 Greetings
10:15-11:05 Noga Alon
11:05-11:25 Coffee break
11:25-12:15 Gil Kalai
12:15-14:00 Lunch break to attendees (catering)
14:00-14:50 Nati Linial

2019
Apr
29

11:00am to 1:00pm

CS B-500, Safra campus

Speaker: Karthik C. Srikanta (Weizmann Institute)
Title: On Closest Pair Problem and Contact Dimension of a Graph
Abstract: Given a set of points in a metric space, the Closest Pair problem asks to find a pair of distinct points in the set with the smallest distance. In this talk, we address the fine-grained complexity of this problem which has been of recent interest. At the heart of all our proofs is the construction of a family of dense bipartite graphs with special embedding properties and are inspired by the construction of locally dense codes.

2019
Apr
08

11:00am to 1:00pm

CS B-500, Safra campus

Speaker: Kim Minki, Technion
Title: The fractional Helly properties for families of non-empty sets
Abstract:
Let $F$ be a (possibly infinite) family of non-empty sets.
The Helly number of $F$ is defined as the greatest integer $m = h(F)$ for which there exists a finite subfamily $F'$ of cardinality $m$ such that every proper subfamily of $F'$ is intersecing and $F'$ itself is not intersecting.
For example, Helly's theorem asserts that the family of all convex sets in $d$-dimensional Euclidean space has Helly number $d+1$.

2018
Dec
31

11:00am to 1:00pm

CS bldg, room B500, Safra campus Givat Ram

Speaker: Zur Luria, JCE
Title: On the threshold for simple connectivity in random 2-complexes
Abstract: