• Search Research Projects
  • Search Researchers
  • How to Use
  1. Back to project page

1999 Fiscal Year Final Research Report Summary

Galois groups and fundamental groups

Research Project

Project/Area Number 09440011
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field Algebra
Research InstitutionKYOTO UNIVERSITY

Principal Investigator

IHARA Yasutaka  RIMS, KYOTO UNIVERSITY PROFESSOR, 数理解析研究所, 教授 (70011484)

Co-Investigator(Kenkyū-buntansha) TSUJI Takeshi  RIMS, KYOTO UNIVERSITY INSTRUCTOR, 数理解析研究所, 助手 (40252530)
MOCHIZUKI Shinichi  RIMS, KYOTO UNIVERSITY ASSOCOATE PROFESSOR, 数理解析研究所, 助教授 (10243106)
TAMAGAWA Akio  RIMS, KYOTO UNIVERSITY ASSOCOATE PROFESSOR, 数理解析研究所, 助教授 (00243105)
MATSUMOTO Makoto  GRADUATE SCHOOL OF SCIENCES, KYUSHU UNIV., ASSOCOATE PROFESSOR, 大学院・数理学研究科, 助教授 (70231602)
NAKAMURA Hiroaki  DEPT. OF MATH., TOKYO METROPOLITAN UNIV., ASSOCIATE PROFESSOR, 理学部, 助教授 (60217883)
Project Period (FY) 1997 – 1999
KeywordsGalois group / Fundamental group / The projective line minus 3 points / Grothendieck-Teichmuller group / Adelic beta function / Hyperadelic gamma function / The stable derivation algebra / Arithmetic of cyclotomic fields
Research Abstract

If X is a geometrically connected algebraic variety over a field k, and XィイD4-ィエD4 =X 【cross product】 kィイD4-ィエD4, kィイD4-ィエD4 being an algebraic closure of k, then the absolute Galois group GィイD2kィエD2=Gal(kィイD4-ィエD4/k) of k acts outerly on the algebraic fundamental group πィイD21ィエD2(XィイD4-ィエD4) of XィイD4-ィエD4 in a natural manner.
The head investigator Ihara continued his study on the arithmetic aspects of this action in the most basic case where k=Q (the rational number filed) and X=PィイD11ィエD1-{0,1,∞} (the projective line minus three points). In this case, πィイD21ィエD2 (XィイD4-ィエD4) is a free profinite group (FィイD4^ィエD4)ィイD22ィエD2 of rank 2, on which GィイD2QィエD2 acts faithfully. GィイD2QィエD2, regarded as a subgroup of the automorphism group Aut(FィイD4^ィエD4)ィイD22ィエD2, is known to be contained in a subgroup GT of Aut(FィイD4^ィエD4)ィイD22ィエD2 (the Grothendieck-Teichmuller group). It is not known whether GィイD2QィエD2≠GT, but there are some properties known to be satisfied by elements of GィイD2QィエD2 but unkno … More wn and doubtful whether they are satisfied by "any" element of GT.
Ihara completed his study of the GT-action on the maximal meta-abelian quotient of (FィイD4^ィエD4)ィイD22ィエD2 [1]. It concerns with the theory of adelic beta functions and their г-decompositions, continuing previous works of G. Anderson and Ihara himself. This contains a certain arithmetic necessary condition for an element σ ∈ GT to belong to GィイD2QィエD2 in terms of the (hyper adelic) gamma function гィイD2σィエD2 and certain quasi 1-cocycles. In [2], more basic arithmeticconditions (in terms of quasi 1-cocycles) and geometric conditions (a reflection of the circumstances that cyclic covers of XィイD4-ィエD4 can also be embedded as open subspaces of XィイD4-ィエD4) are discussed, and logical dependencies among these conditions are clarified.
In[3], Ihara studied the GィイD2QィエD2 action ψィイD1(pィエD1) on the maximal prop-p quotient FィイD3(pィエD3),ィイD22ィエD2 of (FィイD4^ィエD4)ィイD22ィエD2 (p ; an arbitrary fixed prime), in connection with (i) abelian extensions over the cyclotomic filed Q(μィイD2pィエD2∞),(ii) the stable derivation algebra. Among them, (i) concerns with the kernel of ψィイD1pィエD1; asking which abelian extension of Q(μィイD2pィエD2∞) is contained in the field corresponding to this kernel, while (ii)is a sort of the "graded Lie algebra version over Z" of GT, and is a basic object in studying the image of ψィイD1(pィエD1). The main innovation of [3] is the clarification of the connection between (i) (ii), and some numerical result which shows quite an exciting phenomenon related to (i) (ii) when p is an irregular prime. Less

  • Research Products

    (12 results)

All Other

All Publications (12 results)

  • [Publications] Ihara, Yasutaka: "On beta and gamma functions associated with the Grothendieck-Teichmuller group"in "Aspects of Galois Theory", London Math. Soc. LNS. 256. 144-179 (1999)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Ihara, Yasutaka: "On beta and gamma functions associated with the Grothendieck-Teichmuller group"Preprint, (January 1999), to appear in J. Reine Angew. Math.. (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Ihara, Yasutaka: "Some arithmetic aspects of Galois actions on the pro-p fundamental group of P^1-{0,1,∞}"Preprint, (May 1999), to appear in AMS Contemporary Math.. (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Tamagawa, Akio: "On the fundamental groups of curves over algebraically closed fields of characteristic > 0"International Mathematics Research Notices. No. 16. 853-873 (1999)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Nakamura, Hiroaki: "Limits of Galois representations in fundamental groups along maximal degeneration of marked curves, I"American Journal of Mathematics. 121. 315-358 (1999)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Nakamura, Hiroaki (with L.Sehneps): "On a subgkroup of the Grothendieck-Teichmuller group acting on the tower of profinite Teichmuller modular group"Preprint, to appear in Inv. Math. (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Ihara, Yasutaka: "On beta and gamma functions associated with the Grothendieck-Teichmuller group"in "Aspects of Galois Theory", London Math. Soc. LNS. 256. 144-179 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Ihara, Yasutaka: "On beta and gamma functions associated with the Grothendieck-Teichmuller group.II"Preprint,(January 1999), to appear in J.Reine Angew. Math. (2000)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Ihara, Yasutaka: "Some arithmetic aspects of Galois actions on the Pro-p fundamental group of PィイD11ィエD1-{0, 1, ∞}"Preprint, (May 1999), to appear in AMS Contemporary Math.. (2000)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Tamagawa, Akio: "On the fundamental groups of curves over algebraically closed fields of characteristic >0"International Mathematics Research Notices. No.16. 853-873 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Nakamura, Hiroaki: "Limits of Galois representation in funda-mental groups along maximal degeneration of marked curves, I"American Journal of Mathematics. 121. 315-358 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Nakamura, Hiroaki: "On a subgroup of the Grothendieck-Teichmuller group acting on the tower of profinite Teichmuller modular group,(with L.Schneps)"Preprint 1999, to appear in Inv. Math. (2000)

    • Description
      「研究成果報告書概要(欧文)」より

URL: 

Published: 2001-10-23  

Information User Guide FAQ News Terms of Use Attribution of KAKENHI

Powered by NII kakenhi