Integral Domains Which Admit at Most Two Star Operations

In this article, we characterize domains which admit at most two star operations in the integrally closed and Noetherian cases. We also precisely count the number of star operations on an h-local Prüfer domain.     

Star operations and theD+M construction

In this paper, we study star operations on integral domains of the formD+M. In particular, we give an example of a star operation which is not comparable to thet-operation. Supported in part by a National Security Agency Grant.     

Toeplitz quantization and asymptotic expansions for real bounded symmetric domains

An analogue of the star product, familiar from deformation quantization, is studied in the setting of real bounded symmetric domains. The analogue turns out to be a certain invariant operator, which one might call star restriction, from functions on the hermitification of the domain into functions on the domain itself. In particular, we establish the usual (i.e. semiclassical) asymptotic expansion of this star restriction, and further obtain a real- variable analogue of a theorem of Arazy and ?rsted concerning the analogous expansion for the Berezin transform.     

Toeplitz Quantization and Asymptotic Expansions: Peter–Weyl Decomposition

We obtain the Peter–Weyl decomposition of the star product and star restriction associated to the Toeplitz calculus on complex and real symmetric domains, respectively, under the action of the maximal compact subgroup. Both the Berezin and the Berezin–Toeplitz cases are covered.     

Semistar Linkedness and Flatness,Prüfer Semistar Multiplication Domains

Abstract

In 1994, Matsuda and Okabe introduced the notion of semistar operation, extending the “classical” concept of star operation. In this paper, we introduce and study the notions of semistar linkedness and semistar flatness which are natural generalizations, to the semistar setting, of their corresponding “classical” concepts. As an application, among other results, we obtain a semistar version of Davis' and Richman's overring-theoretical theorems of characterization of Prüfer domains for Prüfer semistar multiplication domains.     

Star operations on modules

We present a theory of (semi)star operations for torsion-free modules. This extends the analogous theory of star operations on domains as in [R. Gilmer, Multiplicative Ideal Theory, M. Dekker, New York, 1972] and its generalization to semistar operations studied in [A. Okabe, R. Matsuda, Semistar operations on integral domains, Math. J. Toyama Univ. 17 (1994) 1–21], and recovers some closure operations defined on modules. We investigate some properties of (semi)star operations on a given module over a domain D and their relation with the properties of some classes of semistar operations induced on D.Among other things, this leads to a connection between semistar operations on the D-module and localizing systems on the domain D.     

On the existence,uniqueness and regularity of the exterior stokes problem in R3

Conditions, under which a solution exls-ts, and 1s, unique for the statlonarp ftofces, pattern in exterior domains, in R³are dlscussed. The domains, constdered are the complements. In R³ of lounded star shaped-sets and the class of functions, for which existence ta. dlsplayed have "physically reasonable" lehavlor at infinity. 7hls class is. characterized ly, a finite Dieichlet intearal. We use a method that employs, a variational formulation of the p-rollem and avoids, the use of a Helmhoetz decomposltlon of vector fields in unlounded domains     

Integral domains having a unique Kronecker function ring

We study the class of integrally closed domains having a unique Kronecker function ring, or equivalently, domains in which the completion (or b-operation) is the only e.a.b star operation of finite type. Such domains are a generalization of Prüfer domains and have fairly simple sets of valuation overrings. We give characterizations by studying valuation overrings and integral closure of finitely generated ideals. We provide new examples of such domains and show that for several well-known classes of integral domains the property of having a unique Kronecker function ring makes them fall into the class of Prüfer domains.     

On the number of primitive lattice points in plane domains

We discuss the error term in the asymptotic formula for the number of integral points with coprime coordinates in star like plane domains assuming the validity of the Riemann Hypothesis.     

A new frequency‐uniform coercive boundary integral equation for acoustic scattering

A new boundary integral operator is introduced for the solution of the soundsoft acoustic scattering problem, i.e., for the exterior problem for the Helmholtz equation with Dirichlet boundary conditions. We prove that this integral operator is coercive in L²(Γ) (where Γ is the surface of the scatterer) for all Lipschitz star‐shaped domains. Moreover, the coercivity is uniform in the wavenumber k = ω/c, where ω is the frequency and c is the speed of sound. The new boundary integral operator, which we call the “star‐combined” potential operator, is a slight modification of the standard combined potential operator, and is shown to be as easy to implement as the standard one. Additionally, to the authors' knowledge, it is the only second‐kind integral operator for which convergence of the Galerkin method in L²(Γ) is proved without smoothness assumptions on Γ except that it is Lipschitz. The coercivity of the star‐combined operator implies frequency‐explicit error bounds for the Galerkin method for any approximation space. In particular, these error estimates apply to several hybrid asymptoticnumerical methods developed recently that provide robust approximations in the high‐frequency case. The proof of coercivity of the star‐combined operator critically relies on an identity first introduced by Morawetz and Ludwig in 1968, supplemented further by more recent harmonic analysis techniques for Lipschitz domains. © 2011 Wiley Periodicals, Inc.     

Density of multivariate homogeneous polynomials on star like domains

The famous Weierstrass theorem asserts that every continuous function on a compact set in ${\mathbb{R}}^d$ can be uniformly approximated by algebraic polynomials. A related interesting problem consists in studying the same question for the important subclass of homogeneous polynomials containing only monomials of the same degree. The corresponding conjecture claims that every continuous function on the boundary of convex 0-symmetric bodies can be uniformly approximated by pairs of homogeneous polynomials. The main objective of the present paper is to review the recent progress on this conjecture and provide a new unified treatment of the same problem on non convex star like domains. It will be shown that the boundary of every 0-symmetric non convex star like domain contains an exceptional zero set so that a continuous function can be uniformly approximated on the boundary of the domain by a sum of two homogeneous polynomials if and only if the function vanishes on this zero set. Thus the Weierstrass type approximation problem for homogeneous polynomials on non convex star like domains amounts to the study of these exceptional zero sets. We will also present an extension of a theorem of Varjú which describes the exceptional zero sets for intersections of star like domains. These results combined with certain transformations of the underlying region will lead to the discovery of some new classes of convex and non convex domains for which the Weierstrass type approximation result holds for homogeneous polynomials.     

星极小格星半环

借鉴格环和格半环的定义,在星环、星半环的基础上,增加了一个偏序关系＂≤＂,引入了星极小格星环、星极小格星半环、和负星半环等的定义.进一步介绍了它们的一些性质,并得到了与格环和格半环类似的几个重要的命题.其中主要结论之一是得到了在星环R上引入一种偏序关系＂≤＂,使R成为一个星极小格星环,且恰以R的子星半环S为其负星半环的一个充分必要条件.     

HARDY'S INEQUALITIES WITH MAXIMIZERS FOR W~(1,p) FUNCTIONS ON BOUNDED STAR DOMAINS

With the help of a radially invariant vector field, we derive inequalities of the Hardy kind, with no boundary terms, for W~(1,p) functions on bounded star domains. Our results are not obtainable from the classical inequalities for W_0~(1,p) functions. Unlike in W_0~(1,p),our inequalities admit maximizers that we describe explicitly.     

Functorial Properties of Star Operations

We define a universal star operation to be an assignment *: A ? * _A of a star operation * _A on A to every integral domain A. Prime examples of universal star operations include the divisorial closure star operation v, the t-closure star operation t, and the star operation w = F _∞ of Hedstrom and Houston. For any universal star operation *, we say that an extension B ? A of integral domains is *-ideal class linked if there is a group homomorphism Cl_{* A} (A) → Cl_{* B} (B) of star class groups induced by the map I ? (IB)^{* _B} on the set of * _A -ideals I of A. We study several natural subclasses of the class of *-ideal class linked extensions.     

杨辉三角形的若干性质

研究了杨辉三角中的D av id星恒等式,给出了n阶星恒等式的定义,证明了n(n 3)阶星恒等式的存在性,并且给出了构造n阶星恒等式的方法.     

集值映射的伪(*)连续与弱(*)连续性

本文引入了集值映射的伪（＊）连续性与弱（＊）连续性概念的定义,研究了伪（＊）连续、（＊）连续及弱（＊）连续的等价关系,最后研究了乘积空间中的集值映射成为伪（＊）连续和弱（＊）连续的充要条件。     

超图的强星色数

图的星色数的概念是由Ａ．Ｖｉｎｃｅ（１９８８）首次提出来的,它是图的色数的一个自然而又重要的推广,Ｌ．Ｈａｄａｄ等人（１９９４）将这一概念推广到一致超图,定义了ｈ－一致超图的强（弱）星色数,这里我们给出一般超图的强星色数的概念,研究了它的基本性质,计算了３－一致循环超图的强星色数,它们的强星色数形成了一个严格介于３和４之间的递减序列．     

关于双顶边星图的优美性

在文献[1]中,C.Hoede and H.Kuiper证明了所有的轮都是优美图;文献[2]又指出了所有的齿轮图也是优美图.本文将给出在齿轮图每个齿的顶端加上两条长度为1的边所得的图亦为优美图.     

图的好符号星控制数

引入了图的好符号星控制的概念,求出了欧拉图、完全二部图、完全图和轮图的好符号星控制数,并改进了图的符号星控制数的两个上界.