共查询到20条相似文献,搜索用时 15 毫秒
1.
Eero Hyry 《manuscripta mathematica》1999,98(3):377-390
Let A be a normal local ring which is essentially finite type over a field of characteristic zero. Let I⊂A be an ideal such that the Rees algebra R
A
(I) is Cohen–Macaulay and normal. In this paper we address the question: “When does R
A
(I) have rational singularities?” In particular, we study the connection between rational singularities of R
A
(I) and the adjoint ideals of the powers I
n
(n∋ℕ).
Received: 25 May 1998 / Revised version: 20 August 1998 相似文献
2.
Alessandra Bertapelle 《Mathematische Annalen》2000,316(3):437-463
3.
J. Matejaš 《Numerische Mathematik》2000,87(1):171-199
Summary. A quadratic convergence bound for scaled Jacobi iterates is proved provided the initial symmetric positive definite matrix has simple eigenvalues. The bound is expressed in terms of the off-norm of the scaled initial matrix and the minimum relative gap in the spectrum. The obtained result can be used to predict the stopping moment in the two-sided and especially in the one-sided Jacobi method. Received October 31, 1997 / Revised version received March 8, 1999 / Published online July 12, 2000 相似文献
4.
Ferruccio Orecchia 《manuscripta mathematica》1999,98(3):391-401
In this paper we extend the properties of ordinary points of curves [10] to ordinary closed points of one-dimensional affine reduced schemes and then to ordinary subvarieties of codimension one. Received: 20 March 1998 / Revised version: 7 July 1998 相似文献
5.
6.
Henri Lombardi 《Mathematische Zeitschrift》2002,242(1):23-46
Résumé. Nous démontrons un Nullstellensatz qui établit une équivalence entre l'existence d'une identité algébrique d'un certain type,
d'une part, et l'impossibilité de trouver une suite croissante de variétés irréductibles répondant à certaines contraintes
d'autre part. De ce point de vue le Nullstellensatz usuel correspond au cas des variétés réduites à un point. Nous établissons
aussi un Nullstellensatz formel du même type, en relation avec les suites croissantes d'idéaux premiers. Un cas particulier
important est donné par la notion de suite pseudo régulière, plus générale que la notion de suite régulière. Nous obtenons
de cette manière une nouvelle caractérisation de la dimension de Krull d'un anneau : un anneau a une dimension de Krull si et seulement si il existe une suite pseudo régulière de longueur dans l'anneau. Dans les cas où ces résultats peuvent avoir une signification constructive précise, nos preuves y aboutissent
constructivement. Nous pensons avoir donné ainsi quelques éléments en vue d'une interprétation constructive de la théorie
de la dimension de Krull des anneaux commutatifs. Notre méthode utilise la notion de structure algébrique dynamique introduite
dans des articles précédents.
Received: 4 October 1999; in final form: 11 October 2000 / Published online: 25 June 2001 相似文献
7.
S. Hiltunen 《Monatshefte für Mathematik》2000,129(2):109-117
We prove a Frobenius theorem for Banach space complemented subbundles of the tangent bundle of a manifold modelled on locally
convex spaces. The proof is based on an implicit function theorem for maps from locally convex spaces to Banach spaces proved
in a recent paper of the author.
(Received 15 March 1999; in revised form 2 June 1999) 相似文献
8.
Ahmed Ayache Mabrouk Ben Nasr Othman Echi Noômen Jarboui 《Mathematische Zeitschrift》2001,238(4):695-731
For a ring extension is called a universally catenarian pair if every domain , is universally catenarian. When R is a field it is shown that the only universally catenarian pairs are those satisfying . For several satisfactory results are given. The second purpose of this paper is to study going-down pairs (Definition 5.1). We
characterize these pairs of rings and we establish a relationship between universally catenarian, going-down and residually
algebraic pairs.
Received: 1 July 1999; in final form: 5 June 2000 / Published online: 17 May 2001 相似文献
9.
Shigefumi Mori 《Mathematische Annalen》2001,319(3):533-537
A hyperplane section theorem by R. V. Gurjar [3] is given a short proof. Power series in any number (at least three) of variables
satsifying the condition of the theorem are explicitly constructed. In the course of the proof, the restrictive-looking condition
of the theorem is given an easy sufficient condition from the view point of the weighted projective spaces.
Received April 12, 2000 / Accepted August 21, 2000 / Published online October 30, 2000 相似文献
10.
11.
Ruled Weingarten surfaces in Minkowski 3-space 总被引:1,自引:0,他引:1
We characterize all ruled surfaces in Minkowski 3-space with a relation between the Gauss and mean curvature (Weingarten surfaces).
It turns out that, except if the rulings are in a null direction, these are given by Lorentzian screw motions of straight
lines. However, if the rulings are always in a null direction, then every ruled surface is Weingarten.
Received: 9 February 1998 / Revised version: 20 December 1998 相似文献
12.
B. Ammann 《manuscripta mathematica》2000,101(1):1-22
The Willmore conjecture states that any immersion of a 2-torus into euclidean space satisfies . We prove it under the condition that the L
p
-norm of the Gaussian curvature is sufficiently small.
Received: 10 June 1999 相似文献
13.
Dimitrios Poulakis 《Monatshefte für Mathematik》2000,129(2):139-145
On the reduction modulo
p
of absolutely irreducible polynomials. Let K be a number field and F(X,Y) be an absolutely irreducible polynomial of K[X,Y]. In this note, using an effective version of Riemann-Roch theorem and a version of the implicit functions theorem, we calculate
a positive number A such that if ℘ is prime ideal of the ring of integers of K with norm , then the reduction of F(X,Y) modulo ℘ is an absolutely irreducible polynomial.
(Réu le 1 Février 1999; en forme finale 21 Septembre 1999) 相似文献
14.
Summary.
We present generalizations of the nonsymmetric Levinson and Schur algorithms
for non-Hermitian Toeplitz matrices with some singular or
ill-conditioned
leading principal submatrices. The underlying recurrences allow us to
go from any pair of successive well-conditioned leading principal submatrices
to any such pair of larger order. If the look-ahead step size between
these pairs is bounded, our generalized Levinson and Schur recurrences
require $ operations, and the Schur recurrences can be combined
with recursive doubling so that an $ algorithm results.
The overhead (in operations and storage) of look-ahead steps is very small.
There are various options for applying these algorithms to solving linear
systems with Toeplitz matrix.
Received July 26, 1993 相似文献
15.
Moshe Jarden 《代数通讯》2013,41(4):1467-1494
In this paper we establish several equivalent conditions for a commutative ring in which every principal ideal is a finite intersection of prime power ideals to be a general ZPI-ring. Using these results, we establish some equivalent conditions for a commutative ring in which every principal ideal is a finite intersection of primary ideals to be a general ZPI-ring. 相似文献
16.
Bogdan Dumitrescu 《Numerische Mathematik》1998,79(4):485-499
Fast matrix multiplication algorithms of Strassen and Winograd are known to have weaker numerical accuracy than usual (inner
product) multiplication. In this paper, we show that scaling usually improves accuracy when operands have elements of widely
varying magnitude. We also propose estimators for numerical errors, based on samples of the result. All these estimators can
be computed in operations. Experiments prove the effectiveness of the scaling idea and of the absolute error estimator.
Received February 20, 1996/ Revised version received July 1, 1997 相似文献
17.
Summary. In this paper, we are concerned with a matrix equation
where A is an real matrix and x and b are n-vectors. Assume that an approximate solution is given together with an approximate LU decomposition. We will present fast algorithms for proving nonsingularity of A and for calculating rigorous error bounds for . The emphasis is on rigour of the bounds. The purpose of this paper is to propose different algorithms, the fastest with
flops computational cost for the verification step, the same as for the LU decomposition. The presented algorithms exclusively use library routines for LU decomposition and for all other matrix and vector operations.
Received June 16, 1999 / Revised version received January 25, 2001 / Published online June 20, 2001 相似文献
18.
A four-variable distribution on permutations is derived, with two dual combinatorial interpretations. The first one includes
the number of fixed points “fix”, the second the so-called “pix” statistic. This shows that the duality between derangements
and desarrangements can be extended to the case of multivariable statistics. Several specializations are obtained, including
the joint distribution of (des, exc), where “des” and “exc” stand for the number of descents and excedances, respectively.
Authors’ addresses: Dominique Foata, Institut Lothaire, 1 rue Murner, F-67000 Strasbourg, France; Guo-Niu Han, Center for
Combinatorics, LPMC, Nankai University, Tianjin 300071, P.R. China; I.R.M.A. UMR 7501, Université Louis Pasteur et CNRS, 7,
rue René-Descartes, F-67084 Strasbourg, France 相似文献
19.
Summary. Let be a square matrix dependent on parameters and , of which we choose as the eigenvalue parameter. Many computational problems are equivalent to finding a point such that has a multiple eigenvalue at . An incomplete decomposition of a matrix dependent on several parameters is proposed. Based on the developed theory two new algorithms are
presented for computing multiple eigenvalues of with geometric multiplicity . A third algorithm is designed for the computation of multiple eigenvalues with geometric multiplicity but which also appears to have local quadratic convergence to semi-simple eigenvalues. Convergence analyses of these methods
are given. Several numerical examples are presented which illustrate the behaviour and applications of our methods.
Received December 19, 1994 / Revised version received January 18, 1996 相似文献
20.
J.M. Peña 《Numerische Mathematik》1998,81(2):293-304
Pivoting strategies for Gaussian elimination leading to upper triangular matrices which are diagonally dominant by rows are
studied. Forward error analysis of triangular systems whose coefficient matrices are diagonally dominant by rows is performed.
We also obtain small bounds of the backward errors for the pivoting strategies mentioned above. Our examples of matrices include
H-matrices and some generalizations of diagonally dominant matrices, and scaled partial pivoting for the 1-norm is an example
of these pivoting strategies. In the case of an
M-matrix, a pivoting strategy of computational complexity is proposed, which satisfies all the results of the paper.
Received June 6, 1997 / Revised version received October 27, 1997 相似文献