Calabi–Yau threefolds with non-Gorenstein involutions

The concept of non-Gorenstein involutions on Calabi–Yau threefolds is a higher dimensional generalization of non-symplectic involutions on K3 surfaces. We present some elementary facts about Calabi–Yau threefolds with non-Gorenstein involutions. We give a classification of the Calabi–Yau threefolds of Picard rank one with non-Gorenstein involutions, whose fixed locus is not zero-dimensional.     

Periods of singular double octic Calabi–Yau threefolds and modular forms

By the modularity theorem, every rigid Calabi–Yau threefold X has associated modular form f such that the equality of L-functions $L(X,s)=L(f,s)$ holds. In this case, period integrals of X are expected to be expressible in terms of the special values $L(f,1)$ and $L(f,2)$. We propose a similar interpretation of period integrals of a nodal model of X. It is given in terms of certain variants of a Mellin transform of f. We provide numerical evidence toward this interpretation based on a case of double octics.     

Remarks on nef and movable cones of hypersurfaces in Mori dream spaces

We investigate nef and movable cones of hypersurfaces in Mori dream spaces. The first result is: Let Z be a smooth Mori dream space of dimension at least four whose extremal contractions are of fiber type of relative dimension at least two and let X be a smooth ample divisor in Z, then X is a Mori dream space as well.The second result is: Let Z be a Fano manifold of dimension at least four whose extremal contractions are of fiber type and let X be a smooth anti-canonical hypersurface in Z, which is a smooth Calabi–Yau variety, then the unique minimal model of X up to isomorphism is X itself, and moreover, the movable cone conjecture holds for X, namely, there exists a rational polyhedral cone which is a fundamental domain for the action of birational automorphisms on the effective movable cone of X.The third result is: Let $P:={\mathbb{P}}^n\times ?\times {\mathbb{P}}^n$ be the N-fold self-product of the n-dimensional projective space. Let X be a general complete intersection of $n+1$ hypersurfaces of multidegree $(1,\dots ,1)$ in P with $\dim ?X\ge 3$. Then X has only finitely many minimal models up to isomorphism, and moreover, the movable cone conjecture holds for X.     

A Characterization of Counterexamples to the Kodaira-Ramanujam Vanishing Theorem on Surfaces in Positive Characteristic

The author gives a characterization of counterexamples to the Kodaira-Ramanujam vanishing theorem on smooth projective surfaces in positive characteristic. More precisely, it is reproved that if there is a counterexample to the Kodaira-Ramanujam vanishing theorem on a smooth projective surface X in positive characteristic, then X is either a quasi-elliptic surface of Kodaira dimension 1 or a surface of general type. Furthermore, it is proved that up to blow-ups, X admits a fibration to a smooth projective curve, such that each fiber is a singular curve.     

Vanishing viscosity limit for the 3D magnetohydrodynamic system with generalized Navier slip boundary conditions

In this paper, we investigate the vanishing viscosity limit problem for the 3D incompressible magnetohydrodynamic (MHD) system in a general bounded smooth domain of R ³ with the generalized Navier slip boundary conditions. We also obtain rates of convergence of the solution of viscous MHD to the corresponding ideal MHD. Copyright © 2016 John Wiley & Sons, Ltd.     

Vanishing conditions for the simplicial volume of compact complex varieties

Gromov has defined a notion of simplicial volume: it is a topological invariant for compact manifolds which is closely related to the fundamental group. We investigate here the relevance of this notion in the realm of complex varieties.

     

Galois Theory for the Selmer Group of an Abelian Variety

This paper concerns the Galois theoretic behavior of the p-primary subgroup Sel _A (F) _p of the Selmer group for an Abelian variety A defined over a number field F in an extension K/F such that the Galois group G(K/F) is a p-adic Lie group. Here p is any prime such that A has potentially good, ordinary reduction at all primes of F lying above p. The principal results concern the kernel and the cokernel of the natural map s _K/F Sel _A (F) _p Sel _A (K) _p ^G(K/F) where F is any finite extension of F contained in K. Under various hypotheses on the extension K/F, it is proved that the kernel and cokernel are finite. More precise results about their structure are also obtained. The results are generalizations of theorems of B.Mazurand M. Harris.     

A Vanishing Theorem for the Tangential de Rham Cohomology of a Foliation with Amenable Fundamental Groupoid

For a space X carrying a foliation , the authors study the cohomology of the complex of differential forms which are smooth along the leaves and transversally locally L . It is shown that, if the leaves are nonpositively curved manifolds of rank at least r in a suitable uniform sense and the fundamental groupoid of the foliation is amenable, then the cohomology vanishes in degrees above r. This result is inspired by some of Gromov's results on bounded cohomology.     

第二型曲线积分的中值定理

引入了定义在曲线上的函数的介值性概念,函数的介值性要弱于其连续性,作为该概念的特殊情形,一元函数的介值性定义比李衍禧所给的定义更宽松.同时引入了关于坐标无反向的曲线的概念.在此基础上证明了定义在关于坐标无反向的曲线上的函数的第二型曲线积分的中值定理.李衍禧和关若峰的主要结果及熟知的定积分中值定理均是主要结果的简单推论.     

Extremal functions for sharp Moser–Trudinger type inequalities in the whole space RN

In this paper, we prove the existence of maximizers for the sharp Moser–Trudinger type inequalities in whole space ${\mathbb{R}}^N$, $N\ge 2$ with more general nonlinearity. The main key in our proof is a precise estimate of the concentrating level of the Moser–Trudinger functional associated with our inequalities on the normalized concentrating sequences. This estimate solves a heavily non-trivial and open problem related to the sharp Moser–Trudinger inequality. Our method gives an alternative proof of the existence of maximizers for the Moser–Trudinger inequality and singular Moser–Trudinger inequality in whole space ${\mathbb{R}}^N$ due to Li and Ruf [30] and Li and Yang [31] without using blow-up analysis argument.     

A Decomposition Theorem for Higher-Order Sturm-Liouville Problems on the Line and Numerical Approximation of the Spectrum

In this work, we present a decomposition of the scattering matrix for higher-order Sturm-Liouville problems in terms of scattering matrices associated to disjointly supported potentials. Consequently, we propose a numerical method to approximate the eigenvalue problem. It is shown that the theory and numerics apply to the non self-adjoint case.     

渐近非扩张型半群殆轨道的强遍历收敛定理

设H是一个Hilbert空间,G是一个右可逆拓扑半群,在G上引入渐近殆非扩张曲线u(·),将具等距的渐进殆非扩张曲线的遍历定理应用到非Lipschitzian右可逆半群的殆轨道,证明了渐近非扩张型半群殆轨道的强遍历收敛定理,推广了已有的结果.     

Banach空间中渐近非扩张型半群的遍历定理

对带Opial条件的Banach空间中非扩张半群的不动点理论进行推广,得到了带Opial条件的Banach空间中渐近非扩张型半群的遍历收敛定理.     

两参数Ito型随机微分方程解的收敛定理

设ωｚ是Ｒ＾２＋上的布朗单,考虑两参数Ｉｔｏ型随机微分方程：ｄｘｚ＝ａ（ｚ,ｘｚ）ｄωｚ＋ｂ（ｚ,ｘｚ）ｄｚ（１）ｄｘ＾＊ｚ＝ａｚ（ｚ,ｘ＾＊ｚ）ｄωｚ＋ｂｚ（ｚ,ｘ＾＊ｚ）ｄｚ（２）则在方程系数满足一定条件下,本证明了方程（２）的解向方程（１）的解收敛。     

A Theorem of Beurling-sLax Type for Hilbert Spaces of Functions Analytic in the Unit Ball

Schur multipliers on the unit ball are operator-valued functions for which the N-variable Schwarz-Pick kernel is nonnegative. In this paper, the coefficient spaces are assumed to be Pontryagin spaces having the same negative index. The associated reproducing kernel Hilbert spaces are characterized in terms of generalized difference-quotient transformations. The connection between invariant subspaces and factorization is established.     

The Comparison Theorem for Bergman and Kobayashi Metrics on Cartan-Hartogs Domain of the Third Type

In this paper, we give the holomorphic sectional curvature under invariant Kähler metric on a Cartan-Hartogs domain of the third type Y _III (N,q,K) and construct an invariant Kähler metric, which is complete and not less than the Bergman metric, such that its holomorphic sectional curvature is bounded above by a negative constant. Hence we obtain a comparison theorem for the Bergman and Kobayashi metrics on Y _III (N,q,K).