Freiman's theorem

In mathematics, Freiman's theorem is a combinatorial result in additive number theory. In a sense it accounts for the approximate structure of sets of integers that contain a high proportion of their internal sums, taken two at a time.

The formal statement is:

Let A be a finite set of integers such that the sumset

is small, in the sense that

for some constant . There exists an n-dimensional arithmetic progression of length

that contains A, and such that c' and n depend only on c.[1]

A simple instructive case is the following. We always have

with equality precisely when A is an arithmetic progression.

This result is due to Gregory Freiman (1964,1966).[2] Much interest in it, and applications, stemmed from a new proof by Imre Z. Ruzsa (1994). Mei-Chu Chang proved new polynomial estimates for the size of arithmetic progressions arising in the theorem in 2002.[3]

Green and Ruzsa (2007) generalized the theorem for arbitrary abelian groups: here A can be contained in the sum of a generalized arithmetic progression and a subgroup — the name of such sets is coset-progression.

See also

References

  1. ↑ Nathanson (1996) p.251
  2. ↑ Nathanson (1996) p.252
  3. ↑ Chang, Mei-Chu (2002). "A polynomial bound in Freiman's theorem". Duke Math. J. 113 (3): 399–419. doi:10.1215/s0012-7094-02-11331-3. MR 1909605.
  • Freiman, G.A. (1964). "Addition of finite sets". Sov. Math., Dokl. 5: 1366–1370. Zbl 0163.29501.
  • Freiman, G. A. (1966). Foundations of a Structural Theory of Set Addition (in Russian). Kazan: Kazan Gos. Ped. Inst. p. 140. Zbl 0203.35305.
  • Freiman, G. A. (1999). "Structure theory of set addition". Astérisque. 258: 1–33. Zbl 0958.11008.
  • Nathanson, Melvyn B. (1996). Additive Number Theory: Inverse Problems and Geometry of Sumsets. Graduate Texts in Mathematics. 165. Springer. ISBN 0-387-94655-1. Zbl 0859.11003.
  • Ruzsa, Imre Z. (1994). "Generalized arithmetical progressions and sumsets". Acta Mathematica Hungarica. 65 (4): 379–388. doi:10.1007/bf01876039. Zbl 0816.11008.
  • Ruzsa, Imre Z.; Green, Ben (2007). "Freiman's theorem in an arbitrary abelian group". London Math. Soc. 75 (1): 163–175. arXiv:math/0505198. doi:10.1112/jlms/jdl021.

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