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Recent Posts
 TYI 41: How many steps does it take for a simple random walk on the discrete cube to reach the uniform distribution?
 Gil’s Collegial Quantum Supremacy Skepticism FAQ
 Amazing! Keith Frankston, Jeff Kahn, Bhargav Narayanan, Jinyoung Park: Thresholds versus fractional expectationthresholds
 Starting today: Kazhdan Sunday seminar: “Computation, quantumness, symplectic geometry, and information”
 The story of Poincaré and his friend the baker
 Gérard Cornuéjols’s baker’s eighteen 5000 dollars conjectures
 Noisy quantum circuits: how do we know that we have robust experimental outcomes at all? (And do we care?)
 Test Your Intuition 40: What Are We Celebrating on Sept, 28, 2019? (And answer to TYI39.)
 Quantum computers: amazing progress (Google & IBM), and extraordinary but probably false supremacy claims (Google).
Top Posts & Pages
 Gil's Collegial Quantum Supremacy Skepticism FAQ
 TYI 41: How many steps does it take for a simple random walk on the discrete cube to reach the uniform distribution?
 Lior, Aryeh, and Michael
 TYI 30: Expected number of Dice throws
 Elchanan Mossel's Amazing Dice Paradox (your answers to TYI 30)
 Quantum computers: amazing progress (Google & IBM), and extraordinary but probably false supremacy claims (Google).
 Amazing: Hao Huang Proved the Sensitivity Conjecture!
 Jeff Kahn and Jinyoung Park: Maximal independent sets and a new isoperimetric inequality for the Hamming cube.
 Aubrey de Grey: The chromatic number of the plane is at least 5
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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
10 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