| Research Abstract |
Appell's hypergeometric function F_2(a; b, b'; c, c'; x, y) =Σ^^∞__<m,n=0>((a,m+n)(b,m)(b',n))/((c,m)(c',n)(1,m)(1,n))x^my^n, where(a,n) = Γ(a+n)/Γ(a), satisfies a system E_2(a;b,b';c,c') of differential equations on the (x,y)-space X (【similar or equal】P^2).
1. I tabulated all the systems of parameters (a;b,b';c,c') into six classes such that each E_2(a;b,b';c,c') has a finite irreducible monodromy group. These monodromy groups have reflection subgroups whose Shephard-Todd numbers are 2,28,30 and 32.
2. The system E: = E_2(-1/<12>;1/6;1/<12>;1/3;1/2) has the biggest finite irreducible monodromy group G of order 12・25920. A Schwarz map s_E of E defined by the ratio of four linearly independent solutions of E is a 25920-valued map of X-Sing(E) into P^3, where Sing(E) denotes the singular locus of E. The closure S of the image of s_E turns out to be an irreducible hypersurface of degree 90 on which G acts.
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