Hilbert空间中C_o-半群族指数稳定性

主要讨论了Hilbert空间中Co-半群族Th(t)指数稳定问题,证明了满足||Th(t)||≤Meσt(M,σ与h无关)的半群族Th(t)指数稳定与弱Lp-稳定是等价的,并且给出了另外的三个判定Th(t)指数稳定的等价条件.     

Hilbert空间中C0-半群族指数稳定性

主要讨论了Hilbert空间中Co-半群族Th(t)指数稳定问题，明了满足||Th(t)||≤Me^σt(M,σ与h无关）的半群族Th(t)指数稳定与弱L^p-稳定是等价的，并且给出了另外的三个判定Th(t)指数稳定的等价条件。     

带奇性的非线性抛物方程边值问题

本文讨论非线性奇异抛物方程第一边值问题解的存在性、唯一性、稳定性以及当t充分大时解的渐近性态．利用先验估计的方法得到：存在唯一的光滑正解，解在L^1范数意义下连续依赖于初值．t充分大时，||u-u↑-||L^2收敛于一个常数．     

关于2R（w2R）范数的一个注记

证明了自反Banach空间X上的等价w2R范数全体构成一个剩余集;同时证明了X闭子空间上等价的w2R范数均可延拓为X上等价的w2R范数.特别地,当X是可分时,上述w2R范数可替换为2R范数.     

平面上一类光滑凸曲线流

研究平面上一类严格凸曲线流(?F(u,t))/(?t)=(p(u,t)-Φ(t))N(u,t),F(u,t)是平面上的曲线族,p(u,t)是支撑函数,Φ(t)是C~∞光滑函数,N(u,t)是单位内法向量.当初始曲线F(u,0)严格凸并且Φ(t)满足适当条件时,证明了发展曲线保持凸性不变,曲线流在发展过程中具有全局存在性,且当时间t趋于无穷大时曲线在C~∞范数下收敛到有限圆.     

Banach空间上一类由算子导出的局部凸拓扑

本文我们研究了由半范簇｛ＰＴ｜Ｔ∈ψ（Ｅ，Ｅ１）｝在Ｅ上导出的局部凸拓扑σＥ（Ｅ１），其中ＰＴ（ｘ）＝Ｔｘ的范数，ｘ∈Ｅ。首先我们给出了拓扑σＥ（Ｅ１）＝ω和σＥ（Ｅ１）＝Ｅ上的范数的等价条件，接着讨论了在σＥ（Ｅ１）下的紧性与完备性，最后利用空间稠密特征和关于无穷基数幂等的Ｈｅｓｓｅｎｂｅｒｇ定理进一步研究了σＥ（Ｅ１）与Ｅ上的范数的关系，证明了当Ｅ的稠密特征足够大时在ω和Ｅ上的范数间有无穷多个     

任意矩阵的特征值的扰动界

Hoffman和Wielandt对A和C都是正规矩阵(即AA~H=A~HA,A~H表示A的共轭转置矩阵)的情形给出了σ的一个上界为||B||_F,其中||·||_F表示矩阵的Frobenius(或Euclld)范数([9]和[10]分别对A,C均为对称矩阵和Hermite矩阵时证明了这一结果).但他们也指出,当A和C至少有一个不是正规矩阵时,这个界不成立.于是,如何推广Hoffman和Wielandt的结果(下面简称为W-H定理),一直成为人们感兴趣的课题.     

半群上的非交换调和分析

设Ａ（Ｍ）是 Ｃ＊－代数（ｖｏｎ Ｎｅｕｍａｎｎ代数）．本文证明了，若φ是定义在Ｒ＋上取值于Ａ（Ｍ）的范数连续的有界正定函数，则φ可表示为Ｒ＋上取值于Ａ＇＇（Ｍ）的有界半变差向量测度的Ｌａｐｌａｃｅ变换．同时也证明了取值于Ａ（Ｍ）的Ｈａｍｂｕｒｇｅｒ型的矩量问题．     

半参数回归模型中二阶段估计的渐近性质

给定半参数回归模型Y＝X′β g(T) e,其中β∈R^p是未知参数向量,g(t)是定义在[0,1]上的未知函数,e是随机误差,本文研究了β,,g(t)和σ2的估计量βn,gn(t)和σn^2,在适当的条件下证明了它们的渐近正态性,并给出了gn(t)的最优收敛速度。     

复超球上μ-不变的BMO函数

关于单位圆上的BMO函数,Baernstein定义了调和测度意义下与通常BMO范数等价的范数,并指出赋以这种范数的BMO函数空间在单位圆自同构群下是不变的。本文以Rudin的复超球函数论为工具,证明了球上Poisson核所定义的调和测度意义的BMO范数,与拟距离意义的BMO范数之间的等价性。作为推论,得到复超球的BMO函数空间在Mbius变换群下的不变性;以及BMO和BMOA函数的两个必要充分条件。     

Norms on earthquake measures and Zygmund functions

The infinitesimal earthquake theorem gives a one-to-one correspondence between Thurston bounded earthquake measures and normalized Zygmund bounded functions. In this paper, we provide an intrinsic proof of a theorem given in an earlier paper by the author; that is, we show that the cross-ratio norm of a Zygmund bounded function is equivalent to the Thurston norm of the earthquake measure in the correspondence.

     

J rgens结果的一个新证明

文章研究有界线性算子半群的扰动问题 .在一定条件下 ,我们表明 :设算子 B生成最终依范连续半群 S(t) (t τ) ,K是有界线性算子 .如果‖ K R(σ+iτ,B) K‖→ 0 ,τ→∞ ,那么算子 A =B +K生成的半群 T(t) ,t>2τ是依范连续的 .我们将此结果应用于迁移算子 ,给出 J rgens结果的一个新证明 .     

关于非线性Lipschitz算子的Sderlind猜想

设ｆ是以Ｌ（ｆ）为最小上界Ｌｉｐｓｃｈｉｔｚ常数、以ρ（ｆ）为谱域半径、以ｒ（ｆ）为Ｇｅｒｓｃｈｇｏｒｉｍ域半径的有限维非线性Ｌｉｐｓｃｈｉｔｚ算子．本文证明了“存在等价范数‖·‖使Ｌ（ｆ）＝ｒ（ｆ）”的Ｓｄｅｒｌｉｎｄ猜想；给出反例否定了Ｓｄｅｒｌｉｎｄ的另一个猜想：“存在等价范数‖·‖使Ｌ（ｆ）ｒ（ｆ）”（注意ｒ（ｆ）与ｒ（ｆ）的区别），同时也否定了“ε＞０，存在等价范数‖·‖ε使Ｌε（ｆ）ρ（ｆ）＋ε”的猜想．作为以上所获结论的应用，本文将有关Ｄａｕｇａｖｅｔ方程的相应结果推广到了非线性算子情形．     

Symmetries of Null Geometry in Indefinite Kenmotsu Manifolds

Null hypersurfaces have metrics with vanishing determinants and this degeneracy of these metrics leads to several difficulties. In this paper, null hypersurfaces of indefinite Kenmotsu space forms, tangent to the structure vector field, are studied with specific attention to locally symmetric, semi-symmetric and Ricci semi-symmetric null hypersurfaces. We show that locally symmetric and semi-symmetric null hypersurfaces are totally geodesic and parallel. These also hold for Ricci semi-symmetric null hypersurfaces, under a certain condition. We prove that, in null Einstein hypersurfaces of an indefinite Kenmotsu space form, tangent to the structure vector field, the local symmetry, semisymmetry and Ricci semi-symmetry notions are equivalent. For totally contact umbilical null hypersurfaces, we show that there are η-“Weyl” connections adapted to the induced structure on the null hypersurface.     

Frobenius–Ehresmann structures and Cartan geometries in positive characteristic

The aim of the present paper is to lay the foundation for a theory of Ehresmann structures in positive characteristic, generalizing the Frobenius-projective and Frobenius-affine structures defined in the previous work. This theory deals with atlases of étale coordinate charts on varieties modeled on homogeneous spaces of algebraic groups, which we call Frobenius–Ehresmann structures. These structures are compared with Cartan geometries in positive characteristic, as well as with higher-dimensional generalizations of dormant indigenous bundles. In particular, we investigate the conditions under which these geometric structures are equivalent to each other. Also, we consider the classification problem of Frobenius–Ehresmann structures on algebraic curves. The latter half of the present paper discusses the deformation theory of indigenous bundles in the algebraic setting. The tangent and obstruction spaces of various deformation functors are computed in terms of the hypercohomology groups of certain complexes. As a consequence, we formulate and prove the Ehresmann–Weil–Thurston principle for Frobenius–Ehresmann structures. This fact asserts that deformations of a variety equipped with a Frobenius–Ehresmann structure are completely determined by their monodromy crystals.     

厄米特矩阵的迹的几点性质

应用矩阵Ａ＝（ａｉｊ）∈Ｃｎ×ｎ的弗罗伯尼范数ＡＦ和谱范数ＡＳ，研究厄米特矩阵的迹的性质，得到几个结论：Ｔｒ（ＡＢ）＝∑ｎｉ＝１λｉ∑ｎｊ＝１ｔｉｊμｊ（λｉ，μｊ分别为Ａ，Ｂ的特征值，０≤ｔｉｊ≤１，且∑ｎｉ＝１ｔｉｊ＝１，ｊ＝１，２，…，ｎ）；Ｔｒ（ＡＢ）≤Ｔｒ（Ａ）ＢＳ；Ｔｒ（ＡＢ）Ｈ（ＡＢ）］≤Ｔｒ（ＡＨＡ）［ｍａｘ１≤ｉ≤ｎλｉ］２（λｉ是Ｂ的特征值）等．     

正則的嘉當空間極小超曲面的柯什密德不變量和附屬微分方程

<正> 本文是繼作者前篇論文之後的;目的在於詳細研究該文末節所論的關於拓廣的微小變形問題.和芬斯拉空間相類似地有E.Cartan所建立的以面積概念為基礎的     

Some theoretical comparisons of refined Ritz vectors and Ritz vectors

Refined projection methods proposed by the author have received attention internationally. We are concerned with a conventional projection method and its refined counterpart for computing approximations to a simple eigenpair (A, x) of a large matrix A. Given a subspace ω that contains an approximation to x, these two methods compute approximations (μ,x) and (μ,x) to (λ, x), respectively. We establish three results. First, the refined eigenvector approximation or simply the refined Ritz vector x is unique as the     

The Thurston norm, fibered manifolds and twisted Alexander polynomials

Every element in the first cohomology group of a 3-manifold is dual to embedded surfaces. The Thurston norm measures the minimal ‘complexity’ of such surfaces. For instance the Thurston norm of a knot complement determines the genus of the knot in the 3-sphere. We show that the degrees of twisted Alexander polynomials give lower bounds on the Thurston norm, generalizing work of McMullen and Turaev. Our bounds attain their most concise form when interpreted as the degrees of the Reidemeister torsion of a certain twisted chain complex. We show that these lower bounds give the correct genus bounds for all knots with 12 crossings or less, including the Conway knot and the Kinoshita-Terasaka knot which have trivial Alexander polynomial.We also give obstructions to fibering 3-manifolds using twisted Alexander polynomials and detect all knots with 12 crossings or less that are not fibered. For some of these it was unknown whether or not they are fibered. Our work in particular extends the fibering obstructions of Cha to the case of closed manifolds.