共查询到20条相似文献,搜索用时 31 毫秒
1.
《Journal of Pure and Applied Algebra》1997,122(3):323-328
F-rational rings are defined for rings of characteristic p > 0 using the Frobenius endomorphism and corresponds to rational singularities in characteristic 0. We study F-rationality of certain Rees algebras and prove that every Cohen-Macaulay local ring with isolated singularity and negative a-invariant has a Rees algebra which is F-rational. As a consequence, we find that “Boutot's Theorem” asserting that a pure subring of a rational singularity is a rational singularity is not true for a F-rational ring. 相似文献
2.
Gil Kalai 《Israel Journal of Mathematics》1983,45(4):337-351
Let
(n, k) be the class of all simplicial complexesC over a fixed set ofn vertices (2≦k≦n) such that: (1)C has a complete (k−1)-skeleton, (2)C has precisely (
k
n−1
)k-faces, (3)H
k
(C)=0. We prove that for
,H
k−1(C) is a finite group, and our main result is:
. This formula extends to high dimensions Cayley’s formula for the number of trees onn labelled vertices. Its proof is based on a generalization of the matrix tree theorem. 相似文献
3.
David Fried 《Journal of Fixed Point Theory and Applications》2009,6(1):87-92
When X is a finite complex and p1X\pi_{1}X acts on
\mathbbR2{\mathbb{R}}^2 by translations we give criteria involving H2X for an equivariant map
F : [(X)\tilde] ? \mathbbR2F : \tilde{X} \rightarrow {\mathbb{R}}^2 to be onto. Following work of Manning and Shub, this leads to entropy bounds related to Shub’s entropy conjecture. 相似文献
4.
In this paper we investigate the upper bounds on the numbers of transitions of minimum and maximum spanning trees (MinST and
MaxST for short) for linearly moving points. Here, a transition means a change on the combinatorial structure of the spanning
trees. Suppose that we are given a set ofn points ind-dimensional space,S={p
1,p
2, ...p
n
}, and that all points move along different straight lines at different but fixed speeds, i.e., the position ofp
i
is a linear function of a real parametert. We investigate the numbers of transitions of MinST and MaxST whent increases from-∞ to +∞. We assume that the dimensiond is a fixed constant. Since there areO(n
2) distances amongn points, there are naivelyO(n
4) transitions of MinST and MaxST. We improve these trivial upper bounds forL
1 andL
∞ distance metrics.
Letk
p
(n) (resp.
) be the number of maximum possible transitions of MinST (resp. MaxST) inL
p
metric forn linearly moving points. We give the following results in this paper: κ1(n)=O(n
5/2
α(n)),κ
∞(n)=O(n
5/2
α(n)),
, and
where α(n) is the inverse Ackermann's function. We also investigate two restricted cases, i.e., thec-oriented case in which there are onlyc distinct velocity vectors for movingn points, and the case in which onlyk points move. 相似文献
5.
Jürgen Eckhoff 《Israel Journal of Mathematics》1988,62(3):283-301
LetP be a family ofn boxes inR
d
(with edges parallel to the coordinate axes). Fork=0, 1, 2, …, denote byf
k
(P) the number of subfamilies ofP of sizek+1 with non-empty intersection. We show that iff
r
(P)=0 for somer≦n, then
where thef
k
(n, d, r) are ceg196rtain definite numbers defined by (3.4) below. The result is best possible for eachk. Fork=1 it was conjectured by G. Kalai (Israel J. Math.48 (1984), 161–174). As an application, we prove a ‘fractional’ Helly theorem for families of boxes inR
d
. 相似文献
6.
7.
V. V. Peller 《Journal of Mathematical Sciences》1985,31(1):2709-2712
In this paper there is given a sufficient condition for a Hankel matrix F to belong to the space of Schur multipliers of all bounded operators in
2 (or, what is the same, to the tensor algebra V2). It is shown that ifw is a nonnegative function on T, such that is a sequence of integers, {Fi}j1 is a sequence of polynomials,) and, then FV2. It follows from this that under these conditions F is a multiplier of the space H1, i.e.,.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 135, pp. 113–119, 1984 相似文献
8.
Arrangements and cohomology 总被引:11,自引:0,他引:11
Michael Falk 《Annals of Combinatorics》1997,1(1):135-157
9.
Dionisio Gallarati 《Annali di Matematica Pura ed Applicata》1957,43(1):195-214
Sunto Si dànno delle condizioni necessarie affinchè due superficie algebriche F, G d’una V
3
algebrica non singolare possano presentare contatto d’ordine assegnato q −1 lungo una curva
priva di punti multipli. Si approfondisce sopratuito il caso q=3, con applicazione al problema di determinare le superficie algebriche Gn di S
3
che presentano contatto del 3o ordine lungo una
n con una superficie quartica F
4
. 相似文献
10.
K. R. Apt 《Israel Journal of Mathematics》1978,29(2-3):221-238
The connections between inductive definability and models of comprehension are studied. Let
= 〈A, R
l, ...,R
n 〉 be an infinite structure and letI
φ
be a set inductively defined by a formulaφ of the second order language
. We prove that if
is a model of Δ
1
1
-Comprehension relativized toφ, andφ is
-absolute, then for everyη smaller than the height of
(h(
)),I
φ
is in
. If
is aβ-structure which satisfies Σ
1
1
-Comprehension relativized toφ and WF(X), and φ is
-absolute, thenI
φ
is in
and ‖φ| <h (
). These results imply that Barwise-Grilliot theorem is false in the case of uncountable acceptable structures. We also study
the notion of invariant definability over models1 of Δ
1
1
-Comprehension.
This paper is registered as Report ZW 69/76 of the Mathematical Centre. 相似文献
11.
Vladimir G. Berkovich 《Israel Journal of Mathematics》1995,92(1-3):45-59
Let ϕ:Y →X be a morphism of finite type between schemes of locally finite type over a non-Archimedean fieldk, and letF be an étale constructible sheaf onY. In [Ber2] we proved that if the torsion orders ofF are prime to the characteristic of the residue field ofk then the canonical homomorphisms (R
Q
ϱ*F)an →R
q
ϱ
*
an
F
an are isomorphisms. In this paper we extend the above result to the class of sheavesF with torsion orders prime to the characteristic ofk. 相似文献
12.
Let ? be a family ofk-subsets on ann-setX andc be a real number 0 <c<1. Suppose that anyt members of ? have a common element (t ≧ 2) and every element ofX is contained in at mostc|?| members of ?. One of the results in this paper is (Theorem 2.9): If $$c = {{(q^{t - 1} + ... + q + 1)} \mathord{\left/ {\vphantom {{(q^{t - 1} + ... + q + 1)} {(q^t + ... + q + 1)}}} \right. \kern-\nulldelimiterspace} {(q^t + ... + q + 1)}}$$ . whereq is a prime power andn is sufficiently large, (n >n (k, c)) then The corresponding lower bound is given by the following construction. LetY be a (q t + ... +q + 1)-subset ofX andH 1,H 2, ...,H |Y| the hyperplanes of thet-dimensional projective space of orderq onY. Let ? consist of thosek-subsets which intersectY in a hyperplane, i.e., ?={F∈( k X ): there exists ani, 1≦i≦|Y|, such thatY∩F=H i }. 相似文献
13.
This paper introduces the concept of ‘symmetric centres’ of braided monoidal categories. LetH be a Hopf algebra with bijective antipode over a fieldk. We address the symmetric centre of the Yetter-Drinfel’d module category:
and show that a left Yetter-Drinfel’d moduleM belongs to the symmetric centre of
and only ifM is trivial. We also study the symmetric centres of categories of representations of quasitriangular Hopf algebras and give
a sufficient and necessary condition for the braid of,
Hℳ to induce the braid of
, or equivalently, the braid of
, whereA is a quantum commutativeH-module algebra 相似文献
14.
To any graded Frobenius algebra A we associate a sequence of graded Frobenius algebras A
[n]
so that there is canonical isomorphism of rings (H
*(X;ℚ)[2])
[n]
≅H
*(X
[n]
;ℚ)[2n] for the Hilbert scheme X
[n]
of generalised n-tuples of any smooth projective surface X with numerically trivial canonical bundle.
Oblatum 25-I-2001 & 18-IX-2002?Published online: 24 February 2003 相似文献
15.
Claus Scheiderer 《manuscripta mathematica》1996,91(1):247-281
LetG be a profinite group which has an open subgroupH such that the cohomologicalp-dimensiond≔cdp(H) is finite (p is a fixed prime). The main result of this paper expresses thep-primary part of high degree cohomology ofG in terms of the elementary abelianp-subgroups ofG: From the latter one constructs a natural profinite simplicial setA
G, on whichG acts by conjugation. ThenH
n(G,M)≅H
G
n
(AG,M) holds forn≧d+r and everyp-primary discreteG-moduleM (r≔p-rank ofG). If one uses profinite Farrell cohomology, which is introduced in this paper, the analogous fact holds in all degrees. These
results are the profinite analogues of theorems by K.S. Brown for discrete groups. 相似文献
16.
M. Brodmann 《Archiv der Mathematik》2002,79(2):87-92
Let M be a finitely generated faithful module over a noetherian ring R of dimension d < ¥ \infty and let \mathfrak a \subseteqq R {\mathfrak a} \subseteqq R be an ideal. We describe the (finite) set SuppR(H\mathfrak ad (M)) = AssR(H\mathfrak ad (M)) \textrm{Supp}_R(H_{\mathfrak a}^d (M)) = \textrm{Ass}_R(H_{\mathfrak a}^d (M)) of primes associated to the highest local cohomology module H\mathfrak ad (M) H_{\mathfrak a}^d (M) in terms of the local formal behaviour of \mathfrak a {\mathfrak a} . If R is integral and of finite type over a field, SuppR(H\mathfrak ad (M)) \textrm{Supp}_R(H_{\mathfrak a}^d (M)) is the set of those closed points of X = Spec(R) whose fibre under the normalization morphism n: X¢? X \nu : X' \rightarrow X contains points which are isolated in n-1(Spec(R/\mathfrak a)) \nu^{-1}(\textrm{Spec}(R/{\mathfrak a})) . 相似文献
17.
J. A. S. Martins 《Annali di Matematica Pura ed Applicata》1977,115(1):271-294
Summary Piecewise polynomial and Fourier approximation of functions in the Sobolev spaces
on unbounded domains Θ ⊂ Rn are applied to the study of the type of compact embeddings into appropriate Lebesgue and Orlicz spaces. It is shown that
if Θ and s satisfy certain conditions, the embeddings
, m/n+1/q−1/p>0 and
, Φ being an Orlicz function subordinate to both φ(t)=|t|p
exp |t|n/(n−m) and Φσ(t)=exp |t|σ−1, σ ⩾ 1, m/n>1/p, are of type ls. One result dealing with multiplications maps from
into Lq(Θ) is also obtained.
Entrata in Redazione il 14 ottobre 1976. 相似文献
18.
It is shown that for everyk and everyp≥q≥d+1 there is ac=c(k,p,q,d)<∞ such that the following holds. For every familyℋ whose members are unions of at mostk compact convex sets inR
d
in which any set ofp members of the family contains a subset of cardinalityq with a nonempty intersection there is a set of at mostc points inR
d
that intersects each member ofℋ. It is also shown that for everyp≥q≥d+1 there is aC=C(p,q,d)<∞ such that, for every family
of compact, convex sets inR
d
so that among andp of them someq have a common hyperplane transversal, there is a set of at mostC hyperplanes that together meet all the members of
.
This research was supported in part by a United States-Israel BSF Grant and by the Fund for Basic Research administered by
the Israel Academy of Sciences. 相似文献
19.
Daniel Lehmann 《Annals of Global Analysis and Geometry》1994,12(1):109-122
LetX
1 andX
2 be two holomorphic vector fields on a manifoldV with complex dimensionp. Assume that they have the same singular set . For all
, it is known (after Chern-Bott) that each of the vector fields defines a residual characteristic classC
1(V,X
1)(resp.C
1(V,X
2)) inH
2p
(V, V-), which is a lift of the usual characteristic classC
1
(V) of the tangent bundle. The differenceC
1
(V,X
2)-C
1
(V,X
1) belongs then to the image of in the exact sequence. In fact, there exists a canonical liftC
1
(V,X
1,X
2) of this difference inH
2p–1(V-): we will call itthe residual class of order 2 (associated toI, X
1 andX
2). This class is localized near the points whereX
1 andX
2 are colinear: we will explain this precisely in terms of Grothendieck residues. The formula that we obtain can be interpreted as a generalization of the purely algebraic identity, obtained from the general one as a byproduct: where (
1, , p) and (
1,,
p
) denote two families of non-zero complex numbers, such that all denominators in this formula do not vanish. (This identity corresponds in fact to the case whereX
1 andX
2 are non-degenerate at the same isolated singular point.)If the
i
's (1ip) depend now differentiably (resp. holomorphically) on a real (resp. complex) parametert then, denoting by the derivative with respect tot, and assuming all numbers lying in a denominator not to be 0, we can deduce from the above identity the following derivation formula: 相似文献
20.
Nondas E. Kechagias 《manuscripta mathematica》1994,84(1):261-290
Given an increasing sequence of integersN=(0,n
1,n
2,...), a functorG
N
is constructed from the category
of based spaces of the homotopy type ofCW compleces and based maps to a subcategory
of
in analogy to May's approximation modelC. A family of homology operationsRN is associated toG
N
and its algebraic structure is described in terms of modular coinvariants of parabolic subgroups. 相似文献