| Project/Area Number |
12640084
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geometry
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| Research Institution | Tohoku Gakuin University |
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Principal Investigator |
TSUCHIHASHI Hiroyasu Tohoku Gakuin University, Assistant Professor, 教養学部, 助教授 (00146119)
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| Co-Investigator(Kenkyū-buntansha) |
KONNO Kazuhiro Oosaka University, Assistant Professor, 大学院・理学研究科, 助教授 (10186869)
NAMBA Makoto Oosaka University, Professor, 大学院・理学研究科, 教授 (60004462)
ASHIKAGA Tadashi Tohoku Gakuin University, Professor, 工学部, 教授 (90125203)
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| Project Period (FY) |
2000 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 2002: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2001: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2000: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Galois coverings / fundamental groups / projective plane / Dihedral groups / Symmetric groups / Polydiscs / Differential equations / 射影空間 / 不正則数 / Zariski pair |
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| Research Abstract |
(i) We construct Galois coverings π : X → Y for certain finite groups G containing dihedral groups and symmetric groups such that any Galois covering W → Z of a compact protective variety Z with Gal(W/Z) 【similar or equal】 G, is obtained as the fiber product of π and a rational map from Z to Y. As an application, we show that for any Galois covering of the projective plane with the Galois group isomorphic to the dihedral group of order 2 r(r is odd), the branch locus is defined by a homogeneous polynomial f satisfying fh^2 =g^2_1 + g^r_2 for certain homogeneous polynomials h, g_1 and g_2.
(ii) We compute the fundamental groups of the complements for certain curves on the projective plane. As an application, we obtain a new Zariski pair each curve of which consists of four conics and has only nodes and tacnodes as singularities. Moreover, we give a method computing the fundamental groups of Galois coverings of the projective plane.
(iii) Let X be a Galois covering of the projective plane and let ^^-__X be the minimal resolution of X. We obtain the following results. If every subgroup of Gal(X/P^2) is normal, then the irregularity of ^^-__X is equal to zero. If Gal(X/P^2) is isomorphic to the dihedral group of order 2p (p is an odd prime), then the irregularity of ^^-__X is a multiple of p - 1.
(iv) We classify Galois coverings from projective spaces to theirselves.
(v) We give a method constructing new examples of Galois covering of the projective plane whose universal coverings are isomorphic to the 2-dimensional polydisk or open ball. Moreover, we show how to calculate the differential equations the ratios of whose linearly independent four solutions give uniformizations.
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