You have 3 free guides left 😟
Unlock your guides
You have 3 free guides left 😟
Unlock your guides

5.4 Extensions and generalizations

6 min readjuly 30, 2024

, a cornerstone of additive combinatorics, has inspired numerous extensions and generalizations. These expansions broaden the theorem's scope, tackling multidimensional and polynomial patterns in dense sets, and exploring connections to and .

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

The extensions showcase the theorem's versatility and far-reaching implications. From the to the , these generalizations provide powerful tools for studying arithmetic structures in various mathematical contexts, influencing fields beyond combinatorics.

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Extensions of Szemerédi's Theorem

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Multidimensional and Polynomial Versions

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • The multidimensional Szemerédi theorem states that any subset of Zd\mathbb{Z}^d with positive upper density contains arbitrarily long arithmetic progressions
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • The replaces the arithmetic progression with the image of an integer polynomial, stating that any subset of the integers with positive upper density contains the image of any integer polynomial
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • proved a polynomial Szemerédi theorem for multiple polynomials, showing that any subset of the integers with positive upper density contains a configuration of the form {x+P1(y),x+P2(y),...,x+Pk(y)}\{x+P_1(y), x+P_2(y), ..., x+P_k(y)\} for any integer polynomials P1,...,PkP_1, ..., P_k
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Density Hales-Jewett Theorem and Combinatorial Subspaces

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • The density Hales-Jewett theorem is a far-reaching generalization of Szemerédi's theorem, dealing with higher-dimensional rather than arithmetic progressions
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- It states that for any positive integers $r$ and $k$, there exists a positive integer $n$ such that any $r$-coloring of the $k$-dimensional combinatorial subspaces of $\{1, 2, ..., n\}$ contains a monochromatic combinatorial line
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • Furstenberg and Katznelson proved a density version of the Hales-Jewett theorem, showing that any subset of Zn\mathbb{Z}^n with positive upper density contains a combinatorial line
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- A combinatorial line is a set of the form $\{(x_1, ..., x_{i-1}, t, x_{i+1}, ..., x_n) : t \in \mathbb{Z}\}$ for some fixed $x_1, ..., x_{i-1}, x_{i+1}, ..., x_n$ and $i$
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Significance of Extensions

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Applications in Ergodic Theory and Dynamical Systems

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • The multidimensional Szemerédi theorem has important applications in ergodic theory and the study of dynamical systems, particularly in understanding multiple recurrence phenomena
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- For example, it can be used to show that for any measure-preserving system $(X, \mathcal{B}, \mu, T)$ and any set $A \in \mathcal{B}$ with positive measure, there exists a positive integer $n$ such that $\mu(A \cap T^{-n}A \cap T^{-2n}A) > 0$
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • The generalizations of Szemerédi's theorem have also found applications in number theory, particularly in the study of linear and polynomial patterns in prime numbers and other arithmetically interesting sets
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- For instance, the Green-Tao theorem, which states that the primes contain arbitrarily long arithmetic progressions, can be seen as a consequence of a relative version of Szemerédi's theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Implications for Additive Combinatorics and Related Fields

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • The polynomial Szemerédi theorem and its extensions demonstrate the robustness of Szemerédi's original result, showing that the existence of arithmetic structure is not limited to linear patterns
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • The density Hales-Jewett theorem provides a powerful tool for studying the behavior of dense subsets in high-dimensional spaces, with implications for and other areas of combinatorics
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- It has been used to prove results such as the [Gallai-Witt theorem](https://www.fiveableKeyTerm:Gallai-Witt_Theorem), which states that for any finite coloring of $\mathbb{Z}^n$, there exists a monochromatic set of the form $\{x, x+d, ..., x+kd\}$ for some $x, d \in \mathbb{Z}^n$ and $k \in \mathbb{N}$
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • These extensions have led to the development of new techniques and insights in additive combinatorics, such as the use of ergodic theory and
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Proof Techniques for Generalizations

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Density Increment Arguments and Ergodic Theory

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • The proof of the multidimensional Szemerédi theorem relies on a higher-dimensional version of the used in the original proof, combined with tools from ergodic theory
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- The key idea is to show that if a subset of $\mathbb{Z}^d$ lacks arbitrarily long arithmetic progressions, then it must have a density increment on a smaller subspace
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- This process is repeated until a contradiction is reached, proving the existence of the desired arithmetic progression
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • The density Hales-Jewett theorem is proved using a density increment argument similar to that of Szemerédi's theorem, but with the additional challenge of dealing with the combinatorial structure of the high-dimensional space
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Correspondence Principles and Nilpotent Groups

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • Bergelson and Leibman's proof of the polynomial Szemerédi theorem uses a correspondence principle to reduce the problem to a statement in ergodic theory, which is then proved using multiple recurrence and
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- The correspondence principle relates the existence of polynomial patterns in dense subsets of the integers to the multiple recurrence of certain polynomial functions in a measure-preserving system
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- The ergodic theory statement is then proved using the machinery of nilpotent groups and nilsystems, which provide a natural setting for studying polynomial recurrence
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • Many proofs of extensions and generalizations of Szemerédi's theorem rely on advanced tools from ergodic theory, such as the and the theory of nilsystems
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Higher-Order Fourier Analysis and Quantitative Bounds

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • The use of higher-order Fourier analysis, particularly the , has been instrumental in obtaining quantitative bounds and more efficient proofs for some of these extensions
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- The Gowers uniformity norms, denoted by $\|f\|_{U^k}$, measure the degree to which a function $f$ behaves like a polynomial of degree $k-1$
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- These norms have been used to give quantitative bounds for the multidimensional Szemerédi theorem and to simplify the proof of the density Hales-Jewett theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • Higher-order Fourier analysis has also been used to develop new proof techniques for Szemerédi's theorem and its extensions, such as the so-called "polymath proof" of the density Hales-Jewett theorem, which combines ideas from ergodic theory and higher-order Fourier analysis
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Applications of Szemerédi's Theorem

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Constellations and Polynomial Patterns

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • Use the multidimensional Szemerédi theorem to prove the existence of arbitrarily shaped in dense subsets of the integer lattice
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- For example, show that any subset of $\mathbb{Z}^2$ with positive upper density contains infinitely many copies of any given finite pattern (such as an L-shape or a square)
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • Apply the polynomial Szemerédi theorem to study the distribution of polynomial patterns in dense subsets of the integers, such as the set of prime numbers
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- For instance, prove that there exist infinitely many triples of primes $(p, p+n^2, p+2n^2)$ for some integer $n$
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Ramsey Theory and Combinatorial Subspaces

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • Utilize the density Hales-Jewett theorem to establish Ramsey-type results for high-dimensional combinatorial subspaces
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- For example, prove that for any finite coloring of $\mathbb{Z}^n$, there exists a monochromatic combinatorial subspace of dimension $k$ for any given $k$
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • Combine Szemerédi's theorem with tools from analytic number theory to investigate the behavior of dense subsets of arithmetically interesting sets, such as the Gaussian integers or the ring of polynomials over a finite field
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- Show that any subset of the Gaussian integers with positive upper density contains infinitely many arithmetic progressions of length $k$ for any given $k$
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem

Ergodic Theory and Multiple Recurrence

Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
  • Apply extensions of Szemerédi's theorem in the context of ergodic theory to study multiple recurrence phenomena and the behavior of measure-preserving dynamical systems
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- Prove that for any measure-preserving system $(X, \mathcal{B}, \mu, T_1, ..., T_d)$ and any set $A \in \mathcal{B}$ with positive measure, there exists a positive integer $n$ such that $\mu(A \cap T_1^{-n}A \cap ... \cap T_d^{-n}A) > 0$
Top images from around the web for Extensions of Szemerédi's Theorem
Top images from around the web for Extensions of Szemerédi's Theorem
- Use the polynomial Szemerédi theorem to study multiple recurrence along polynomial sequences, such as showing that for any measure-preserving system $(X, \mathcal{B}, \mu, T)$, any set $A \in \mathcal{B}$ with positive measure, and any integer polynomials $P_1, ..., P_k$, there exists a positive integer $n$ such that $\mu(A \cap T^{-P_1(n)}A \cap ... \cap T^{-P_k(n)}A) > 0$
© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.


© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.

© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.
Glossary
Glossary