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 Open problem session of HUJICOMBSEM: Problem #1, Nati Linial – Turan type theorems for simplicial complexes.
 Péter Pál Pach and Richárd Palincza: a Glimpse Beyond the Horizon
 To cheer you up 14: Hong Liu and Richard Montgomery solved the Erdős and Hajnal’s odd cycle problem
 To cheer you up in difficult times 13: Triangulating real projective spaces with subexponentially many vertices
 Benjamini and Mossel’s 2000 Account: Sensitivity of Voting Schemes to Mistakes and Manipulations
 Test Your Intuition (46): What is the Reason for Maine’s Huge Influence?
 This question from Tim Gowers will certainly cheeer you up! and test your intuition as well!
 Three games to cheer you up.
 Cheerful Test Your Intuition (#45): Survey About Sisters and Brothers
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 Open problem session of HUJICOMBSEM: Problem #1, Nati Linial  Turan type theorems for simplicial complexes.
 Péter Pál Pach and Richárd Palincza: a Glimpse Beyond the Horizon
 To cheer you up 14: Hong Liu and Richard Montgomery solved the Erdős and Hajnal's odd cycle problem
 TYI 30: Expected number of Dice throws
 Elchanan Mossel's Amazing Dice Paradox (your answers to TYI 30)
 This question from Tim Gowers will certainly cheeer you up! and test your intuition as well!
 Cheerful Test Your Intuition (#45): Survey About Sisters and Brothers
 Answer: Lord Kelvin, The Age of the Earth, and the Age of the Sun
 To cheer you up in difficult times 13: Triangulating real projective spaces with subexponentially many vertices
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Monthly Archives: July 2008
A Diamater Problem for Families of Sets.
Let me draw your attention to the following problem: Consider a family of subsets of size d of the set N={1,2,…,n}. Associate to a graph as follows: The vertices of are simply the sets in . Two vertices and are adjacent … Continue reading
Posted in Combinatorics, Convex polytopes, Open problems
10 Comments
Extremal Combinatorics II: Some Geometry and Number Theory
Extremal problems in additive number theory Our first lecture dealt with extremal problems for families of sets. In this lecture we will consider extremal problems for sets of real numbers, and for geometric configurations in planar Euclidean geometry. Problem I: Given a set A of … Continue reading
Arrow’s Economics 1
The annual Summer School in Economics at HU was directed until last year by Kenneth Arrow, along with Eyal Winter. Arrow decided this year to step down as a director and Eric Maskin is replacing him. The 2008 Summer School was … Continue reading
Pushing Behrend Around
Erdos and Turan asked in 1936: What is the largest subset of {1,2,…,n} without a 3term arithmetic progression? In 1946 Behrend found an example with Now, sixty years later, Michael Elkin pushed the the factor from the denominator to the enumerator, … Continue reading
Posted in Combinatorics, Updates
Tagged Arithmetic progressions, Roth's theorem, Szemeredi's theorem
12 Comments
From Helly to Cayley IV: Probability
I decided to split long part III into two parts. This (truly) last part of this series deals with probabilistic problems and with combinatorial questions regarding higher Laplacians. 21. Higher Laplacians and their meanings Our high dimensional extension to Cayley’s … Continue reading
Posted in Combinatorics, Probability
8 Comments
A New RectorElect at the Hebrew University of Jerusalem
Professor Sarah Stroumsa On Wednesday, the Senate of the Hebrew University of Jerusalem elected Professor Sarah Stroumsa (homepage) as the next Rector (provost) of the Hebrew University. For the first time since its establishment, the Hebrew University has elected a woman to its highest post … Continue reading
Helly, Cayley, Hypertrees, and Weighted Enumeration III
This is the third and last part of the journey from a Helly type conjecture of Katchalski and Perles to a Cayley’s type formula for “hypertrees”. (On second thought I decided to divide it into two devoting the second to probabilistic questions.) … Continue reading
Posted in Combinatorics, Convexity, Open problems, Probability
7 Comments