Journal of the Mathematical Society of Japan
Online ISSN : 1881-1167
Print ISSN : 0025-5645
ISSN-L : 0025-5645
Volume 64, Issue 3
Displaying 1-13 of 13 articles from this issue
  • Gopal Prasad, Sai-Kee Yeung
    2012 Volume 64 Issue 3 Pages 683-731
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    The quotient of a Hermitian symmetric space of non-compact type by a torsion-free cocompact arithmetic subgroup of the identity component of the group of isometries of the symmetric space is called an arithmetic fake compact Hermitian symmetric space if it has the same Betti numbers as the compact dual of the Hermitian symmetric space. This is a natural generalization of the notion of “fake projective planes” to higher dimensions. Study of arithmetic fake compact Hermitian symmetric spaces of type An with even n has been completed in [PY1], [PY2]. The results of this paper, combined with those of [PY2], imply that there does not exist any arithmetic fake compact Hermitian symmetric space of type other than An, n ≤ 4 (see Theorems 1 and 2 in the Introduction below and Theorem 2 of [PY2]). The proof involves the volume formula given in [P], the Bruhat-Tits theory of reductive p-adic groups, and delicate estimates of various number theoretic invariants.
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  • Shun Shimomura
    2012 Volume 64 Issue 3 Pages 733-781
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    The discrete second Painlevé equation dPII is mapped to the second Painlevé equation PII by its continuous limit, and then, as shown by Kajiwara et al., a rational solution of dPII also reduces to that of PII. In this paper, regarding dPII as a difference equation, we present a certain asymptotic solution that reduces to a triply-truncated solution of PII in this continuous limit. In a special case our solution corresponds to a rational one of dPII. Furthermore we show the existence of families of solutions having sequential limits to truncated solutions of PII.
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  • Tomohiro Kawakami, Kota Takeuchi, Hiroshi Tanaka, Akito Tsuboi
    2012 Volume 64 Issue 3 Pages 783-797
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    In this paper we study (strongly) locally o-minimal structures. We first give a characterization of the strong local o-minimality. We also investigate locally o-minimal expansions of (R, +, <).
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  • Yu Kawakami, Daisuke Nakajo
    2012 Volume 64 Issue 3 Pages 799-821
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    We give the best possible upper bound for the number of exceptional values of the Lagrangian Gauss map of complete improper affine fronts in the affine three-space. We also obtain the sharp estimate for weakly complete case. As an application of this result, we provide a new and simple proof of the parametric affine Bernstein problem for improper affine spheres. Moreover, we get the same estimate for the ratio of canonical forms of weakly complete flat fronts in hyperbolic three-space.
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  • Kouki Taniyama
    2012 Volume 64 Issue 3 Pages 823-849
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    We define a concept which we call multiplicity. First, multiplicity of a morphism is defined. Then the multiplicity of an object over another object is defined to be the minimum of the multiplicities of all morphisms from one to another. Based on this multiplicity, we define a pseudo distance on the class of objects. We define and study several multiplicities in the category of topological spaces and continuous maps, the category of groups and homomorphisms, the category of finitely generated R-modules and R-linear maps over a principal ideal domain R, and the neighbourhood category of oriented knots in the 3-sphere.
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  • Mitsuhiro Nakao
    2012 Volume 64 Issue 3 Pages 851-883
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    We derive an energy decay estimate for solutions to the initial-boundary value problem of a semilinear wave equation in exterior domains with a nonlinear localized dissipation. Our equation includes an absorbing term like |u|αu, α ≥ 0, and can be regarded as a generalized Klein-Gordon equation at least if α is closed to 0. This observation plays an essential role in our argument.
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  • The Anh Bui
    2012 Volume 64 Issue 3 Pages 885-902
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    Let L be a non-negative self adjoint operator on L2(X) where X is a space of homogeneous type. Assume that L generates an analytic semigroup e-tL whose kernel satisfies the standard Gaussian upper bounds. By the spectral theory, we can define the spectral multiplier operator F(L). In this article, we show that the commutator of a BMO function with F(L) is bounded on Lp(X) for 1 < p < ∞ when F is a suitable function.
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  • Alexander Arhangel′skii, Jan van Mill
    2012 Volume 64 Issue 3 Pages 903-926
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    It is shown that all uniquely homogeneous spaces are connected. We characterize the uniquely homogeneous spaces that are semitopological or quasitopological groups. We identify two properties of homogeneous spaces called skew-2-flexibility and 2-flexibility that are useful in studying unique homogeneity. We also construct a large family of uniquely homogeneous spaces with only trivial continuous maps.
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  • Francesco Guaraldo
    2012 Volume 64 Issue 3 Pages 927-939
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    Some basic results on compact affine Nash groups related to their Nash representations are given. So, first a Nash version of the Peter-Weil theorem is proved and then several more results are given: for example, it is proved that an analytic representation of such a group is of class Nash and that the category of the classes of isomorphic embedded compact Nash groups is isomorphic with that of the classes of isomorphic embedded algebraic groups. Moreover, given a compact affine Nash group G, a closed subgroup H and a homogeneous Nash G-manifold X, it is proved that the twisted product G ×H X is a Nash G-manifold which is Nash G-diffeomorphic to an algebraic G-variety; besides, this algebraic structure is unique.
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  • Gianluca Occhetta, Valentina Paterno
    2012 Volume 64 Issue 3 Pages 941-967
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    In this paper we study smooth complex projective polarized varieties (X,H) of dimension n ≥ 2 which admit a covering family V of rational curves of degree 3 with respect to H such that two general points of X may be joined by a curve parametrized by V, and such that there is a covering family of rational curves of H-degree one.
    We prove that the Picard number of these manifolds is at most three, and that, if equality holds, (X,H) has an adjunction theoretic scroll structure over a smooth variety.
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  • Toshiaki Adachi
    2012 Volume 64 Issue 3 Pages 969-984
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    We study the global behavior of trajectories for Kähler magnetic fields on a connected complete Kähler manifold M of negative curvature. Concerning these trajectories we show that theorems of Hadamard-Cartan type and of Hopf-Rinow type hold: If sectional curvatures of M are not greater than c (< 0) and the strength of a Kähler magnetic field is not greater than $¥sqrt{|c|}$, then every magnetic exponential map is a covering map. Hence arbitrary distinct points on M can be joined by a minimizing trajectory for this magnetic field.
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  • Rafael López, Marian Ioan Munteanu
    2012 Volume 64 Issue 3 Pages 985-1003
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    In the homogeneous space Sol3, a translation surface is parametrized by x(s,t) = α(s) * β(t), where α and β are curves contained in coordinate planes and * denotes the group operation of Sol3. In this paper we study translation surfaces in Sol3 whose mean curvature vanishes.
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  • Ryushi Goto
    2012 Volume 64 Issue 3 Pages 1005-1052
    Published: 2012
    Released on J-STAGE: September 07, 2012
    JOURNAL FREE ACCESS
    Let X0 be an affine variety with only normal isolated singularity at p. We assume that the complement X0 \ {p} is biholomorphic to the cone C(S) of an Einstein-Sasakian manifold S of real dimension 2n − 1. If there is a resolution of singularity π: XX0 with trivial canonical line bundle KX, then there is a Ricci-flat complete Kähler metric for every Kähler class of X. We also obtain a uniqueness theorem of Ricci-flat conical Kähler metrics in each Kähler class with a certain boundary condition. We show there are many examples of Ricci-flat complete Kähler manifolds arising as crepant resolutions.
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