A degenerating family of Riemann surfaces over a Riemann surface gives us a monodromy representation, which is a homomorphism from the fundamental group of a punctured surface to the mapping class group. We show that, given such a homomorphism, if its image is finite, then there exists an (isotrivial) degenerating family of Riemann surfaces whose monodromy representation coincides with it. Moreover, we discuss the special sections of such a degenerating family.

On compact almost complex manifolds, we defined two parabolic flows, which are called the almost Hermitian flow and the almost Hermitian curvature flow in [3]. We show that the uniform equivalence between almost Hermitian metrics and the solution to the almost Hermitian flow by using the method in [6]. This uniform equivalence holds for the almost Hermitian curvature flow as well.

We consider the influence of the number of separated maximum points and Valiron deficiency over the magnitude of Petrenko's deviation of algebroid functions of finite lower order. Presented results are the generalization of Petrenko's and Niino's results. We also give examples showing that the estimates are sharp.

In the authors' previous work, it was shown that if a zero mean curvature C⁴-differentiable hypersurface in an arbitrarily given Lorentzian manifold admits a degenerate light-like point, then the hypersurface contains a light-like geodesic segment passing through the point. The purpose of this paper is to point out that the same conclusion holds with just C³-differentiability of the hypersurfaces.

In the present paper, we prove that, for an odd prime number p and a positive integer g such that g-1 is divisible by p, there exists a Tango curve of genus g in characteristic p.

In this paper, we discuss an asymptotic boundary behavior of the complete Kähler-Einstein metric of negative Ricci curvature on a quasi-projective manifold with semiample log-canonical bundle. In particular, we focus our attention on its relations with degeneration of positivity for the log-canonical bundle on the boundary divisor. Based on a pioneering result due to G. Schumacher, a fundamental conjecture about the relations is proposed in this paper. Moreover it is also proved that the conjecture actually holds in the case when the boundary divisor is of general type.

Let m and n be positive integers, and let p be a prime. Let T(x) = Φ_p^m (Φ_2ⁿ(x)), where Φ_k(x) is the cyclotomic polynomial of index k. In this article, we prove that T(x) is irreducible over Q and that

       {1, θ, θ², ..., θ^{2n-1pm-1(p-1)-1}}

is a basis for the ring of integers of Q(θ), where T(θ) = 0.

The Hurwitz metric was recently defined by Minda by considering a variational problem that involves holomorphic maps from the disc that are globally injective at the origin. In this note, sharp boundary estimates for this metric are obtained on C²-smooth planar domains and as a consequence, it is shown that it is uniformly comparable with the Carathéodory and Kobayashi metrics on such domains. In addition, estimates for the generalized curvatures of this metric are also given.

Let G be a compact Lie group and T its maximal torus. In this paper, we try to compute gr*_γ(G/T) the graded ring associated with the gamma filtration of the complex K-theory K⁰(G/T) for G = Spin(n). In particular, we give a counterexample for a conjecture by Karpenko when G = Spin(17).

It is well known that the Gauss map for a complex plane curve is birational, whereas the Gauss map in positive characteristic is not always birational. Let q be a power of a prime integer. We study a certain plane curve of degree q² + q + 1 for which the Gauss map is inseparable with inseparable degree q. As a special case, we show a relation between the dual curve of the Fermat curve of degree q² + q + 1 and the Ballico-Hefez curve.

New results on the oscillation of solutions of f ″ + A(z)f = 0 and on the growth of solutions of f ″ + A(z)f ′ + B(z)f = 0 are obtained, where A and B are entire functions. Petrenko's magnitudes of deviation of g with respect to ∞ play a key rôle in the results, where g represents one of the coefficients A or B.