Du Val singularity

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In algebraic geometry, a Du Val singularity, also called simple surface singularity, Kleinian singularity, or rational double point, is an isolated singularity of a complex surface which is modeled on a double branched cover of the plane, with minimal resolution obtained by replacing the singular point with a tree of smooth rational curves, with intersection pattern dual to a Dynkin diagram of A-D-E singularity type. They are the canonical singularities (or, equivalently, rational Gorenstein singularities) in dimension 2. They were studied by Patrick du Val [1] [2] [3] and Felix Klein.

Contents

The Du Val singularities also appear as quotients of by a finite subgroup of SL2; equivalently, a finite subgroup of SU(2), which are known as binary polyhedral groups. [4] The rings of invariant polynomials of these finite group actions were computed by Klein, and are essentially the coordinate rings of the singularities; this is a classic result in invariant theory. [5] [6]

Classification

Du Val singularies are classified by the simply laced Dynkin diagrams, a form of ADE classification. Simply Laced Dynkin Diagrams.svg
Du Val singularies are classified by the simply laced Dynkin diagrams, a form of ADE classification.

The possible Du Val singularities are (up to analytical isomorphism):

See also

References

  1. du Val, Patrick (1934a). "On isolated singularities of surfaces which do not affect the conditions of adjunction, Entry I". Proceedings of the Cambridge Philosophical Society . 30 (4): 453–459. doi:10.1017/S030500410001269X. S2CID   251095858. Archived from the original on 9 May 2022.
  2. du Val, Patrick (1934b). "On isolated singularities of surfaces which do not affect the conditions of adjunction, Entry II". Proceedings of the Cambridge Philosophical Society . 30 (4): 460–465. doi:10.1017/S0305004100012706. S2CID   197459819. Archived from the original on 13 May 2022.
  3. du Val, Patrick (1934c). "On isolated singularities of surfaces which do not affect the conditions of adjunction, Entry III". Proceedings of the Cambridge Philosophical Society . 30 (4): 483–491. doi:10.1017/S030500410001272X. S2CID   251095521. Archived from the original on 9 May 2022.
  4. Barth, Wolf P.; Hulek, Klaus; Peters, Chris A.M.; Van de Ven, Antonius (2004). Compact Complex Surfaces. Ergebnisse der Mathematik und ihre Grenzbereiche. 3. Teil (Results of mathematics and their border areas. 3rd Part). Vol. 4. Springer-Verlag, Berlin. pp. 197–200. ISBN   978-3-540-00832-3. MR   2030225. OCLC   642357691. Archived from the original on 2022-05-09. Retrieved 2022-05-09.
  5. Artin, Michael (1966). "On isolated rational singularities of surfaces". American Journal of Mathematics . 88 (1): 129–136. doi:10.2307/2373050. ISSN   0002-9327. JSTOR   2373050. MR   0199191.
  6. Durfee, Alan H. (1979). "Fifteen characterizations of rational double points and simple critical points". L'Enseignement mathématique . IIe Série. 25 (1). European Mathematical Society Publishing House: 131–163. doi:10.5169/seals-50375. ISSN   0013-8584. MR   0543555. Archived from the original on 2022-05-09. Retrieved 2022-05-09.