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A new proof of the density Hales-Jewett theorem (2009)

by D H J Polymath
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A PROBABILISTIC TECHNIQUE FOR FINDING ALMOST-PERIODS IN ADDITIVE COMBINATORICS

by Ernie Croot, Olof Sisask
"... We introduce a new probabilistic technique for finding ‘almost-periods’ of convolutions of subsets of finite groups. This allows us to give probabilistic proofs of two classical results in additive combinatorics: Roth’s theorem on three-term arithmetic progressions and the existence of long arithmet ..."
Abstract - Cited by 32 (3 self) - Add to MetaCart
We introduce a new probabilistic technique for finding ‘almost-periods’ of convolutions of subsets of finite groups. This allows us to give probabilistic proofs of two classical results in additive combinatorics: Roth’s theorem on three-term arithmetic progressions and the existence of long arithmetic progressions in sumsets A +B in Zp. The bounds we obtain for these results are not the best ones known—these being established using Fourier analysis—but they are of a somewhat comparable quality, which is unusual for a method that is completely combinatorial. Furthermore, we are able to find long arithmetic progressions in sets A + B even when both A and B have density close to 1 / logp, which is much sparser than has previously been possible.
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...at have not used Fourier analysis have generally been accompanied by tower-type bounds, establishing only that r3(N) ≪ N/ log ∗ N; see [25, Chapter 10] for references, as well as the more recent work =-=[17]-=-. (The iterated logarithm of N, log ∗ N, is defined to be the number of times it is necessary to take the logarithm of N in order to get a number less than or equal to 1, and thus grows extremely slow...

Tight Lower Bounds for the Size of Epsilon-Nets

by János Pach, Gábor Tardos
"... According to a well known theorem of Haussler and Welzl (1987), any range space of bounded VC-dimension admits an ε-net of size O () ..."
Abstract - Cited by 22 (1 self) - Add to MetaCart
According to a well known theorem of Haussler and Welzl (1987), any range space of bounded VC-dimension admits an ε-net of size O ()

A non-linear lower bound for planar epsilon-nets

by Noga Alon
"... ..."
Abstract - Cited by 14 (1 self) - Add to MetaCart
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The polymath project: lessons from a successful online collaboration in mathematics

by Justin Cranshaw - In Proc. CHI ’11. ACM , 2011
"... Although science is becoming increasingly collaborative, there are remarkably few success stories of online collaborations between professional scientists that actually result in real discoveries. A notable exception is the Polymath Project, a group of mathematicians who collaborate online to solve ..."
Abstract - Cited by 11 (0 self) - Add to MetaCart
Although science is becoming increasingly collaborative, there are remarkably few success stories of online collaborations between professional scientists that actually result in real discoveries. A notable exception is the Polymath Project, a group of mathematicians who collaborate online to solve open mathematics problems. We provide an in-depth descriptive history of Polymath, using data analysis and visualization to elucidate the principles that led to its success, and the difficulties that must be addressed before the project can be scaled up. We find that although a small percentage of users created most of the content, almost all users nevertheless contributed some content that was highly influential to the task at hand. We also find that leadership played an important role in the success of the project. Based on our analysis, we present a set of design suggestions for how future collaborative mathematics sites can encourage and foster newcomer participation. Author Keywords large-scale collaboration, online collaborative mathematics, online collaborative science, online communities
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...ne progress towards an understanding of the problem.” In this strict sense, Polymath1 was successful well beyond Gowers’s expectations. To date there are two journal articles that have been submitted =-=[26, 25]-=-. Additionally, at least two new proofs of the theorem, plus new bounds on Hales-Jewett numbers were discovered. In this work we will examine whether and to what extent Polymath1 was successful in the...

Optimal testing of multivariate polynomials over small prime fields

by Elad Haramaty, Amir Shpilka, Madhu Sudan , 2011
"... We consider the problem of testing if a given function f: Fn q → Fq is close to a n-variate degree d polynomial over the finite field Fq of q elements. The natural, low-query, test for this property would be to pick the smallest dimension t = tq,d ≈ d/q such that every function of degree greater tha ..."
Abstract - Cited by 10 (4 self) - Add to MetaCart
We consider the problem of testing if a given function f: Fn q → Fq is close to a n-variate degree d polynomial over the finite field Fq of q elements. The natural, low-query, test for this property would be to pick the smallest dimension t = tq,d ≈ d/q such that every function of degree greater than d reveals this feature on some t-dimensional affine subspace of Fn q and to test that f when restricted to a random t-dimensional affine subspace is a polynomial of degree at most d on this subspace. Such a test makes only q t queries, independent of n. Previous works, by Alon et al. [AKK + 05], and Kaufman and Ron [KR06] and Jutla et al. [JPRZ04], showed that this natural test rejected functions that were Ω(1)-far from degree d-polynomials with probability at least Ω(q −t) (the results of [KR06] hold for all fields Fq, while the results of [JPRZ04] hold only for fields of prime order). Thus to get a constant probability of detecting functions that were at constant distance from the space of degree d polynomials, the tests made q 2t queries. Kaufman and Ron also noted that when q is prime, then q t queries are necessary. Thus these tests were off by at least a quadratic factor from known lower bounds. It was unclear if the soundness analysis of these tests were tight and this question relates closely to the task
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... to be lower bounded by a very large constant, albeit a constant — specifically it is some sort of Ackerman function of some polynomial in q (in the improved proof of the density Hales-Jewett theorem =-=[Pol09]-=-). Nevertheless it does imply that if log N1(q, d) is sufficiently large as a function of q (a constant we label λq,4), then this allows to conclude that q such “near-parallel” hyperplanes do exist. N...

Graph removal lemmas

by David Conlon, Jacob Fox - SURVEYS IN COMBINATORICS , 2013
"... The graph removal lemma states that any graph on n vertices with o(nv(H)) copies of a fixed graph H may be made H-free by removing o(n²) edges. Despite its innocent appearance, this lemma and its extensions have several important consequences in number theory, discrete geometry, graph theory and com ..."
Abstract - Cited by 9 (3 self) - Add to MetaCart
The graph removal lemma states that any graph on n vertices with o(nv(H)) copies of a fixed graph H may be made H-free by removing o(n²) edges. Despite its innocent appearance, this lemma and its extensions have several important consequences in number theory, discrete geometry, graph theory and computer science. In this survey we discuss these lemmas, focusing in particular on recent improvements to their quantitative aspects.
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...nalytic argument. Recently, a combinatorial proof of the density Hales-Jewett theorem, which is an extension of the multidimensional Szemerédi theorem, was discovered as part of the polymath project =-=[81]-=-. As well as its implications in number theory, the removal lemma and its extensions are central to the area of computer science known as property testing. In this area, one would like to find fast al...

The structure of collaborative problem solving in a virtual math team. Paper presented at the iConference 2011

by Gerry Stahl - In , 2006
"... To develop a science of small-group interaction in groupware, we need a method for analyzing the structure of computer-mediated discourse. Conversation analysis offers an analysis of conversational talk in terms of a fine structure of adjacency pairs and offers some suggestions about longer sequence ..."
Abstract - Cited by 6 (3 self) - Add to MetaCart
To develop a science of small-group interaction in groupware, we need a method for analyzing the structure of computer-mediated discourse. Conversation analysis offers an analysis of conversational talk in terms of a fine structure of adjacency pairs and offers some suggestions about longer sequences built on these pairs. This paper presents a case study of students solving a math problem in an online chat environment. It shows that their problem-solving discourse consists of a sequence of exchanges, each built on a base adjacency pair and each contributing a move in the solution process.
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...of mathematicians recently conducted an online collaborative analysis of a mathematical problem, it took them longer to write the publishable proof than it did to figure out the approach and solve it =-=[4; 6]-=-. Bwang posted the narrative shown in Figure 3 to the Spring Fest wiki. We then move on to understand Team C's formula for summing up the total # of sticks in n-level diamond. We first tried to used t...

A simple proof of the density Hales–Jewett theorem

by Pandelis Dodos, Vassilis Kanellopoulos, Konstantinos Tyros
"... ar ..."
Abstract - Cited by 6 (3 self) - Add to MetaCart
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...rogressions [14] and its multidimensional version [5]. Because of its significance the density Hales–Jewett Theorem has received considerable attention and there are, by now, several different proofs =-=[2, 10, 15]-=-. Our goal in this paper is to give yet another proof of the density Hales–Jewett Theorem that is modeled after Polymath’s proof [10] but places one of its crucial parts in a general conceptual framew...

A density version of the Carlson–Simpson theorem

by Pandelis Dodos, Vassilis Kanellopoulos, Konstantinos Tyros
"... ar ..."
Abstract - Cited by 6 (5 self) - Add to MetaCart
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...s consequences, most notably the famous Szemerédi Theorem on arithmetic progressions [36] and its multidimensional version [13]. The best known upper bounds for the numbers DHJ(k, δ) are obtained in =-=[28]-=- and have an Ackermann-type dependence with respect to k. 1We recall that if w = (wi) n−1 i=0 is a variable word over k of length n, then its wildcard set is defined to be the set { i ∈ {0, ..., n− 1}...

A DENSITY VERSION OF THE HALPERN-LÄUCHLI THEOREM

by Pandelis Dodos, Vassilis Kanellopoulos, Nikolaos Karagiannis , 2010
"... ..."
Abstract - Cited by 5 (4 self) - Add to MetaCart
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