Kakutani fixed-point theorem

theorem that a function f: S→Pow(S) on a compact nonempty convex subset S⊂ℝⁿ, whose graph is closed and whose image f(x) is nonempty and convex for all x∈S, has a fixed point
Thing fixed_point_theorem Q518524
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Kakutani fixed-point theorem

Summary

Kakutani fixed-point theorem is a fixed-point theorem[1]. It draws 122 Wikipedia views per month (fixed_point_theorem category, ranking #3 of 14).[2]

Key Facts

  • Kakutani fixed-point theorem is credited with the discovery of Shizuo Kakutani[3].
  • Kakutani fixed-point theorem's instance of is recorded as fixed-point theorem[4].
  • Shizuo Kakutani is named after Kakutani fixed-point theorem[5].
  • Kakutani fixed-point theorem's subclass of is recorded as fixed-point theorems in infinite-dimensional spaces[6].
  • Kakutani fixed-point theorem's time of discovery or invention is recorded as +1938-00-00T00:00:00Z[7].
  • Kakutani fixed-point theorem's Freebase ID is recorded as /m/07vxx7[8].
  • Kakutani fixed-point theorem's defining formula is recorded as \begin{aligned}&f\colon S\to\operatorname{Pow}(S)\&S\subset\mathbb R^n\&S\ne\varnothing\land\operatorname{conv}(S)=\operatorname{cl}(S)=S\land\sup_{x\in S}|s|<\infty\land{(x,y)\colon y\in f(x)}=\operatorname{cl}({(x,y)\colon y\in f(x)})\land \left(\forall x\in S\colon(f(x)\ne\varnothing \land\operatorname{conv}(f(x))=f(x))\right)\implies\exists s\in S\colon s\in\phi(s)\end{aligned}[9].
  • Kakutani fixed-point theorem's studied by is recorded as convex geometry[10].
  • Kakutani fixed-point theorem's studied by is recorded as topology[11].
  • Kakutani fixed-point theorem's JSTOR topic ID is recorded as kakutani-theorem[12].
  • Kakutani fixed-point theorem's maintained by WikiProject is recorded as WikiProject Mathematics[13].
  • Kakutani fixed-point theorem's Microsoft Academic ID is recorded as 134618013[14].
  • Kakutani fixed-point theorem's generalization of is recorded as Brouwer fixed-point theorem[15].
  • Kakutani fixed-point theorem's OpenAlex ID is recorded as C134618013[16].

Body

Works and Contributions

Kakutani fixed-point theorem is credited with the discovery of Shizuo Kakutani[3].

Why It Matters

Kakutani fixed-point theorem draws 122 Wikipedia views per month (fixed_point_theorem category, ranking #3 of 14).[2] It has Wikipedia articles in 13 language editions, a strong signal of global cultural recognition.[17] It is known by 3 alternative names across languages and contexts.[18]

References

Programmatic citations — every numbered marker resolves to a verifiable graph row below.

Direct Wikidata claims

  1. [4] . wikidata.org.
  2. [3] . wikidata.org.
  3. [5] . wikidata.org.
  4. [6] . wikidata.org.
  5. [7] . wikidata.org.
  6. [8] . Freebase Data Dumps. wikidata.org.
  7. [9] . wikidata.org.
  8. [10] . wikidata.org.
  9. [11] . wikidata.org.
  10. [12] . wikidata.org.
  11. [13] . wikidata.org.
  12. [14] . wikidata.org.
  13. [15] . wikidata.org.
  14. [16] . OpenAlex. Retrieved . docs.openalex.org. Provenance: wikidata.org.

Class ancestry

  1. [1] . Wikidata. wikidata.org.

Aggregate / graph-position facts

  1. [2] . Wikimedia Foundation. dumps.wikimedia.org.
  2. [17] . Wikidata sitelinks. wikidata.org.
  3. [18] . Wikidata aliases. wikidata.org.

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Use these citations when quoting this entity in research, articles, AI prompts, or wherever provenance matters. We aggregate Wikidata + Wikipedia + authoritative open-data sources; the stitched, scored, cross-referenced view is what 4ort.xyz contributes.

APA 4ort.xyz Knowledge Graph. (2026). Kakutani fixed-point theorem. Retrieved May 3, 2026, from https://4ort.xyz/entity/kakutani-fixed-point-theorem
MLA “Kakutani fixed-point theorem.” 4ort.xyz Knowledge Graph, 4ort.xyz, 3 May. 2026, https://4ort.xyz/entity/kakutani-fixed-point-theorem.
BibTeX @misc{4ortxyz_kakutani-fixed-point-theorem_2026, author = {{4ort.xyz Knowledge Graph}}, title = {{Kakutani fixed-point theorem}}, year = {2026}, url = {https://4ort.xyz/entity/kakutani-fixed-point-theorem}, note = {Accessed: 2026-05-03}}
LLM prompt According to 4ort.xyz Knowledge Graph (aggregator of Wikidata, Wikipedia, and authoritative open-data sources): Kakutani fixed-point theorem — https://4ort.xyz/entity/kakutani-fixed-point-theorem (retrieved 2026-05-03)

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