Monoid Domain Constructions of Antimatter Domains

An integral domain without irreducible elements is called an antimatter domain. We give some monoid domain constructions of antimatter domains. Among other things, we show that if D is a GCD domain with quotient field K that is algebraically closed, real closed, or perfect of characteristic p > 0, then the monoid domain D[X; ?⁺] is an antimatter GCD domain. We also show that a GCD domain D is antimatter if and only if P^?1 = D for each maximal t-ideal P of D.     

Cyclic Maximal Ideals of Rings of Differential Operators over Power Series Rings

For an integral domain R, several necessary and sufficient conditions are given for R to be unibranched inside its absolute integral closure; one such condition is that R^pbe Henselian for each prime ideal P of R. Additional conditions are given in case R is a going-down domain. Unlike the situation in the Noetherian context, such going‐down domains R need not be quasilocal or of Krull dimension at most 1. A number of examples are given for the locally pseudo‐valuation domain case     

On finite conductor domains

An integral domain D is a FC domain if for all a, b in D, aDbD is finitely generated. Using a set of very general and useful lemmas, we show that an integrally closed FC domain is a Prüfer v-multiplication domain (PVMD). We use this result to improve some results which were originally proved for integrally closed FC domains (or for coherent domains) to results on PVMD's. Finally we provide examples of integrally closed integral domains which are not FC domains.     

New classes of domains with explicit Bergman kernel

We introduce two classes of egg type domains, built on general bounded sym-metric domains, for which we obtain the Bergman kernel in explicit formulas. As an aux-iliary tool, we compute the integral of complex powers of the generic norm on a boundedsymmetric domains using the well-known integral of Selberg. This generalizes matrix in-tegrals of Hua and leads to a special polynomial with integer or half-integer coefficientsattached to each irreducible bounded symmetric domain.     

Near integral domains II

A direct product decomposition is given for the multiplicative semigroup of a finite near integral domain in terms of the subsemigroup of left identities and a group of automorphisms on the additive group of the domain. Conditions are given which insure that every element will have a uniquen-th root. If there existsx≠0 such that (?x)y=?(xy), for eachy, then the additive group of the near integral domain is abelian. Other conditions sufficient for the commutativity of the additive group are given. An example illustrates that non-isomorphic finite near integral domains can have a left ideal decomposition into Sylow subgroups which are isomorphic as near-rings. Another example shows that an infinite near integral domain need not have a nilpotent additive group, even in the d. g. case. It is conjectured that for each natural numbern there is a near integral domain whose additive group is of nilpotent classn.     

求解二维多区域声波传播问题的一种边界元方法

针对多区域中声波的传播问题,其中每个散射区域的介质是相同的,将散射区域内的声波用一种单双层混合位势的形式来表示,再应用Green定理表示出外部介质区域中的声波,并形成相应的边界积分方程.如果区域个数为M时,传统的边界元方法最终将形成2M个边界积分方程并对应2M个未知函数,而本文的边界元方法最终只形成M个边界积分方程以及对应M个未知函数,从而使得求解的方程和未知数的个数都减少了一倍.最后,通过对数值算例的求解,验证了该方法的可行性及精确性.     

MCD-finite Domains and Ascent of IDF Property in Polynomial Extensions

An integral domain is said to have the IDF property when every non-zero element of it has only a finite number of non-associate irreducible divisors. A counterexample has already been found showing that the IDF property does not necessarily ascend in polynomial extensions. In this paper, we introduce a new class of integral domains, called MCD-finite domains, and show that for any domain D, D[X] is an IDF domain if and only if D is both IDF and MCD-finite. This result entails all the previously known sufficient conditions for the ascent of the IDF property. Our new characterization of polynomial domains with the IDF property enables us to use a different construction and build another counterexample which strengthen the previously known result on this matter.     

Pseudo-almost valuation domains are quasilocal going-down domains,but not conversely

Abstract  Ayman Badawi has recently introduced the PAVDs, a class of (commutative integral) domains which is found strictly between the class of APVDs (“almost pseudo valuation domains”) and that of the (necessarily quasilocal) domains having a linearly ordered prime spectrum. It is known that the latter class strictly contains the class of quasilocal going-down domains; it is proved that the class of quasilocal going-down domains strictly contains the class of PAVDs. Consequently, each seminormal PAVD is a divided domain. Moreover, for each n, 1 ≤ n ≤ ∞, an example is constructed of a divided domain (necessarily a quasilocal going-down domain) of Krull dimension n which is not a PAVD. Keywords Pseudo-almost valuation domain, Prime ideal, Going-down domain, Divided domain, Quasilocal, Valuation overring, Root extension, Seminormal, D+M construction, Krull dimension Mathematics Subject Classification (2000) Primary 13B24, 13G05, Secondary 13A15, 13F05     

Near integral domains on nonabelian groups

In this paper the concept of a special automorphism is introduced and used to analyze near integral domains having nonabelian addtive groups. We show that there are finite and infinite near integral domains having additive groups with arbitrary class of nilpotency. We also give another example of a non-nilpotent group which is the additive group of a near integral domain. Finally, nonabelian groups of order less than 1000 are examined to determine which can be the additive group of a near integral domain.Most of the results of this paper are contained in the author's doctoral dissertation at Boston University. The author thanks ProfessorD. W. Blackett for his guidance.     

矩形到任意多边形区域的Schwarz-Christoffel变换数值解法

运用Schwarz-Christoffel变换方法，建立多边形区域到带状区域共形映射数学模型.对于模型中的约束条件和奇异积分问题，根据Riemann(黎曼)原理，建立复参数与实参数互逆变换，消除非线性系统的约束条件；经过合理积分路径的确定，模型中的奇异积分转化为Gauss-Jacobi(高斯 雅可比)型积分；采用Levenberg-Marquardt算法对非线性系统模型进行求解.根据第一类椭圆函数性质，建立了矩形区域到带状区域共形映射数学模型，通过复参数椭圆函数的计算，得到矩形边界与带状区域边界的关系.最后，对8点对称多边形区域与27点不规则条带状区域计算，将不规则封闭区域边界映射到矩形区域边界，矩形区域内的正交网格，通过变换之后在多边形区域内依然满足正交性，为研究不规则区域到规则区域映射的数值计算奠定基础.     

Prüfer's ascent result via Inc

Let R be an integral domain whose integral closure is a Pr¨fer domain. It is proved that R ? T has the incomparability property for each integral domain T which contains R and is algebraic over R. As a corollary, one has a new proof of Pr¨fer's ascent result, which states that if R is as above and T is the integral closure of R in some field containing R, then T is a Pr¨fer domain.     

Some Remarks on Generalized GCD Domains

An integral domain R is a generalized GCD (GGCD) domain if the semigroup of invertible ideals of R is closed under intersection. In this article we extend the definition of PF-prime ideals to GGCD domains and develop a theory of these ideals which allows us to characterize Prüfer and π -domains among GGCD domains. We also introduce the concept of generalized GCD modules as a natural generalization of GGCD domains to the module case. An R-module M is a GGCD module if the set of invertible submodules of M is closed under intersection. We show that an integral domain R is a GGCD domain if and only if a faithful multiplication R-module M is a GGCD module. Various properties and characterizations of faithful multiplication GGCD modules over integral domains are considered and consequently, necessary and sufficient conditions for a ring R(M), the idealization of M, to be a GGCD ring are given.     

Semiring and Semimodule Issues in MV-Algebras

It is known that an atomic right LCM domain need not be a UFD but is a projectivity-UFD if it is also modular. This paper studies a slightly weaker and easier condition, the RAMP (acronym for the property in the title) , which also ensures that an atomic right LCM domain will be a projectivity-UFD. Among other things it is shown that in an atomic LCM domain, modularity is equivalent to the pair RAMP and LAMP (the left-right analog of RAMP). This result is then used to show that an atomic LCM domain with conjugation is modular. An example is given of an atomic LCM domain that has neither the RAMP nor the LAMP. All rings are not-necessarily commutative integral domains. Recall that an atomic ring is one in which every nonzero nonunit is a product of atoms (i.e. irreducibles) . A ring R is a right LCM domain if for any two elements a and b in R, aR ∩ bR is a principal right ideal. A right LCM domain need not be a left LCM domain [3] . If a ring has both properties it is called an LCM domain. It Is known (see Example 2 below) that, unlike the commutative case, an atomic right LCM domain need not be a UFD (unique factorization domain). In [1] it is shown that if the ring is also modular then it is a projectivity-UFD (definition of the latter recalled below)     

Notes on a new chain condition for prime ideals

A chain condition intermediate to the catenary property and the chain condition for prime ideals (c.c.) is studied. Like the c.c., the condition is inherited from a semi-local domain R by integral extension domains, by local quotient domains, and by factor domains, and a semi-local ring that satisfies the condition is catenary. (Unlike the c.c., none of these statements is true when R is not semi-local.) A number of characterizations of a semi-local domain that satisfies the condition are given in terms of: integral (respectively, algebraic, transcendental) extension domains, Henselizations, completions, Rees rings, associated graded rings and certain discrete valuation over-rings. Then four of the catenary chain conjectures are characterized in terms of this condition.     

Injective modules and semistar operations

We approach the problem of classifying injective modules over an integral domain, by considering the class of semistar Noetherian domains. When working with such domains, one has to focus on semistar ideals: as a consequence for modules, we restrict our study to the class of injective hulls of co-semistar modules, those in which the annihilator ideal of each nonzero element is semistar. We obtain a complete classification of this class, by describing its elements as injective hulls of uniquely determined direct sums of indecomposable injective modules; if moreover, we consider stable semistar operations, then we can further improve this result, obtaining a natural generalization of the classical Noetherian case. Our approach provides a unified treatment of results on injective modules over various kinds of domains obtained by Matlis, Cailleau, Beck, Fuchs and Kim–Kim–Park.     

Uppers to Zero in Polynomial Rings and Prüfer-Like Domains

Let D be an integral domain and X an indeterminate over D. It is well known that (a) D is quasi-Prüfer (i.e., its integral closure is a Prüfer domain) if and only if each upper to zero Q in D[X] contains a polynomial g ∈ D[X] with content c _D (g) = D; (b) an upper to zero Q in D[X] is a maximal t-ideal if and only if Q contains a nonzero polynomial g ∈ D[X] with c _D (g) ^v  = D. Using these facts, the notions of UMt-domain (i.e., an integral domain such that each upper to zero is a maximal t-ideal) and quasi-Prüfer domain can be naturally extended to the semistar operation setting and studied in a unified frame. In this article, given a semistar operation ☆ in the sense of Okabe–Matsuda, we introduce the ☆-quasi-Prüfer domains. We give several characterizations of these domains and we investigate their relations with the UMt-domains and the Prüfer v-multiplication domains.     

Numerical characterizations of some integral domains

Let R be an integral domain. If R satisfies some finiteness conditions, an algorithm that produces the exact list of all distinct overrings of R is established. Then numerical characterizations of several classes of integral domains are obtained.     

Semirigid GCD domains

Let R be a commutative integral domain. An element x of R is calledrigid if for all r,s dividing x; r divides s or s divides r. In our terminology, R issemirigid if each non zero non unit of R is a finite product of rigid elements. We show that semirigid GCD domains have a type of unique factorization, and are a known generalization of Krull domains.     

The number of overrings of an integrally closed domain

We establish in this work a result that gives the number of overrings for any integrally closed domain that has only finitely many overrings; then we provide an algorithm to compute this number. We end this paper with an open problem for integral domains that are not necessarily integrally closed.     

An integral kernel for weakly pseudoconvex domains

A new explicit construction of Cauchy–Fantappié kernels is introduced for an arbitrary weakly pseudoconvex domain with smooth boundary. While not holomorphic in the parameter, the new kernel reflects the complex geometry and the Levi form of the boundary. Some estimates are obtained for the corresponding integral operator, which provide evidence that this kernel and related constructions give useful new tools for complex analysis on this general class of domains.