共查询到20条相似文献,搜索用时 31 毫秒
1.
We prove that any smooth complex projective variety X with plurigenera P
1(X)=P
2(X)=1 and irregularity q(X)=dim(X) is birational to an abelian variety.
Oblatum 26-V-1999 & 13-VI-2000?Published online: 11 October 2000 相似文献
2.
Fabrice Krieger 《Israel Journal of Mathematics》2009,172(1):425-444
Let G be a countable amenable group and P a polyhedron. The mean topological dimension mdim(X,G) of a subshift X ⊂ P
G
is a real number satisfying 0 ≤ mdim(X,G) ≤ dim(P), where dim(P) denotes the usual topological dimension of P. We give a construction of minimal subshifts X ⊂ P
G
with mean topological dimension arbitrarily close to dim(P). 相似文献
3.
Let X be a Stein manifold. Then we prove that for any family ℱ⊂?(X) the normality domain Dℱ) is a meromorphically ?(X)-convex open set of X.
Received: 4 November 1999 相似文献
4.
We fix a prime p and let f(X) vary over all monic integer polynomials of fixed degree n. Given any possible shape of a tamely ramified splitting of p in an extension of degree n, we prove that there exists a rational function φ(X)∈ℚ(X) such that the density of the monic integer polynomials f(X) for which the splitting of p has the given shape in ℚ[X]/f(X) is φ(p) (here reducible polynomials can be neglected). As a corollary, we prove that, for p≥n, the density of irreducible monic polynomials of degree n in ℤ
p
[X] is the value at p of a rational function φ
n
(X)∈ℚ(X). All rational functions involved are effectively computable.
Received: 15 September 1998 / Revised version: 21 October 1999 相似文献
5.
M. Reichaw-Reichbach 《Israel Journal of Mathematics》1963,1(2):61-74
Iff:X →X* is a homeomorphism of a metric separable spaceX into a compact metric spaceX* such thatf(X)=X*, then the pair (f,X*) is called a metric compactification ofX. An absoluteG
δ-space (F
σ-space)X is said to be of the first kind, if there exists a metric compactification (f,X*) ofX such that
, whereG
i are sets open inX* and dim[Fr(G
i)]<dimX. (Fr(G
i) being the boundary ofG
i and dimX — the dimension ofX). An absoluteG
δ-space (F
σ-space), which is not of the first kind, is said to be of the second kind. In the present paper spaces which are both absoluteG
δ andF
σ-spaces of the second kind are constructed for any positive finite dimension, a problem related to one of A. Lelek in [11]
is solved, and a sufficient condition onX is given under which dim [X* −f(X)]≧k, for any metric compactification (f,X*) ofX, wherek≦dimX is a given number.
This research has been sponsored by the U.S. Navy through the Office of Naval Research under contract No. 62558-3315. 相似文献
6.
Antonio Kirson 《Annali dell'Universita di Ferrara》2010,56(2):327-333
An automorphism σ of a projective variety X is said to be wild if σ(Y) ≠ Y for every non-empty subvariety
Y \subsetneq X{Y \subsetneq X} . In [1] Z. Reichstein, D. Rogalski, and J.J. Zhang conjectured that if X is an irreducible projective variety admitting a wild automorphism then X is an abelian variety, and proved this conjecture for dim(X) ≤ 2. As a step toward answering this conjecture in higher dimensions we prove a structure theorem for projective varieties
of Kodaira dimension 0 admitting wild automorphisms. This essentially reduces the Kodaira dimension 0 case to a study of Calabi-Yau
varieties, which we also investigate. In support of this conjecture, we show that there are no wild automorphisms of certain
Calabi-Yau varieties. 相似文献
7.
We consider discrete cocompact isometric actions where X is a locally compact Hadamard space (following [B] we will refer to CAT(0) spaces — complete, simply connected length spaces with nonpositive curvature in the sense of Alexandrov — as Hadamard
spaces) and G belongs to a class of groups (“admissible groups”) which includes fundamental groups of 3-dimensional graph manifolds. We
identify invariants (“geometric data”) of the action which determine, and are determined by, the equivariant homeomorphism type of the action of G on the ideal boundary of X. Moreover, if are two actions with the same geometric data and is a G-equivariant quasi-isometry, then for every geodesic ray there is a geodesic ray (unique up to equivalence) so that . This work was inspired by (and answers) a question of Gromov in [Gr3, p. 136].
Submitted: May 2001. 相似文献
8.
S. S. Podkorytov 《Journal of Mathematical Sciences》2009,161(3):454-459
Homotopy classes of mappings of a compact polyhedron X to the circle T form an Abelian group B(X), which is called the Bruschlinsky group and is cananically isomorphic to H
1 (X; ℤ), Let L be an Abelian group, and let f: B(X) → L be a function. One says that the order of f does not exceed r if for each mapping a: X → T the value f([a]) is ℤ-linearly expressed via the characteristic function I
r
(a): (X × T)
r
→ ℤ of (Γ
a
)
r
, where Γ
a
⊂ X × T is the graph of a. The (algebraic) degree of f is not greater than r if the finite differences of f of order r + 1 vanish. Conjecturally, the order of f is equal to the algebraic degree of f. The conjecture is proved in the case where dim X ≤ 2. Bibliography: 1 title. 相似文献
9.
We deal with (n−1)-generated modules of smooth (analytic, holomorphic) vector fieldsV=(X
1,..., Xn−1) (codimension 1 differential systems) defined locally on ℝ
n
or ℂ
n
, and extend the standard duality(X
1,..., Xn−1)↦(ω), ω=Ω(X1,...,Xn−1,.,) (Ω−a volume form) betweenV′s and 1-generated modules of differential 1-forms (Pfaffian equations)—when the generatorsX
i are linearly independent—onto substantially wider classes of codimension 1 differential systems. We prove that two codimension
1 differential systemsV and
are equivalent if and only if so are the corresponding Pfaffian equations (ω) and
provided that ω has1-division property: ωΛμ=0, μ—any 1-form ⇒ μ=fω for certain function germf. The 1-division property of ω turns out to be equivalent to the following properties ofV: (a)fX∈V, f—not a 0-divisor function germ ⇒X∈V (thedivision property); (b) (V
⊥)⊥=V; (c)V
⊥=(ω); (d) (ω)⊥=V, where ⊥ denotes the passing from a module (of vector fields or differential 1-forms) to its annihilator.
Supported by Polish KBN grant No 2 1090 91 01.
Partially supported by the fund for the promotion of research at the Technion, 100–942. 相似文献
10.
Bohui Chen 《数学学报(英文版)》2010,26(2):209-240
The bubble tree compactified instanton moduli space -Mκ (X) is introduced. Its singularity set Singκ(X) is described. By the standard gluing theory, one can show that- Mκ(X) - Singκ(X) is a topological orbifold. In this paper, we give an argument to construct smooth structures on it. 相似文献
11.
António Marques Fernandes 《Archive for Mathematical Logic》2002,41(1):55-63
In this paper we give a partial answer to a conjecture of Tanaka. We prove that: if WKL0 proves a sentence of the form (∀X)(∃!Y)ψ(X, Y) for a Σ0
3-formula ψ, then so does RCA0.
Received: 12 April 1999 / Published online: 3 October 2001 相似文献
12.
Sigurd Assing 《Probability Theory and Related Fields》2001,120(2):143-167
The paper deals with the infinite-dimensional stochastic equation dX= B(t, X) dt + dW driven by a Wiener process which may also cover stochastic partial differential equations. We study a certain finite dimensional
approximation of B(t, X) and give a qualitative bound for its rate of convergence to be high enough to ensure the weak uniqueness for solutions of
our equation. Examples are given demonstrating the force of the new condition.
Received: 6 November 1999 / Revised version: 21 August 2000 / Published online: 6 April 2001 相似文献
13.
Dr. Matthias Kriesell 《Combinatorica》2006,26(3):277-314
A non-complete graph G is called an (n,k)-graph if it is n-connected but G—X is not (n−|X|+1)-connected for any X ⊂V (G) with |X|≤k. Mader conjectured that for k≥3 the graph K2k+2−(1−factor) is the unique (2k,k)-graph(up to isomorphism).
Here we prove this conjecture. 相似文献
14.
Obstruction Theory and Coincidences in Positive Codimension 总被引:1,自引:0,他引:1
Daciberg GONCALVES Jerzy JEZIERSKI Peter WONG 《数学学报(英文版)》2006,22(5):1591-1602
Let f, g : X→Y be two maps between closed manifolds with dim X ≥ dim Y = n ≥ 3. We study the primary obstruction on(f, g) to deforming f and g to be coincidence free on the n-th skeleton of X. We give examples for which obstructions to deforming f and g to be coincidence free are detected by on (f, g). 相似文献
15.
Daniel W. Cunningham 《Archive for Mathematical Logic》2002,41(1):49-54
Jensen's celebrated Covering Lemma states that if 0# does not exist, then for any uncountable set of ordinals X, there is a Y∈L such that X⊆Y and |X| = |Y|. Working in ZF + AD alone, we establish the following analog: If ℝ# does not exist, then L(ℝ) and V have exactly the same sets of reals and for any set of ordinals X with |X| ≥Θ
L
(ℝ), there is a Y∈L(ℝ) such that X⊆Y and |X| = |Y|. Here ℝ is the set of reals and Θ is the supremum of the ordinals which are the surjective image of ℝ.
Received: 29 October 1999 / Published online: 12 December 2001 相似文献
16.
The maximal Seshadri number μ(L) of an ample line bundle L on a smooth projective variety X measures the local positivity of the line bundle L at a general point of X. By refining the method of Ein-Küchle-Lazarsfeld, lower bounds on μ(L) are obtained in terms of L
n
, n=dim(X), for a class of varieties. The main idea is to show that if a certain lower bound is violated, there exists a non-trivial
foliation on the variety whose leaves are covered by special curves. In a number of examples, one can show that such foliations
must be trivial and obtain lower bounds for μ(L). The examples include the hyperplane line bundle on a smooth surface in ℙ3 and ample line bundles on smooth threefolds of Picard number 1.
Received: 29 June 2001 / Published online: 16 October 2002
RID="⋆"
ID="⋆" Supported by Grant No. 98-0701-01-5-L from the KOSEF.
RID="⋆⋆"
ID="⋆⋆" Supported by Grant No. KRF-2001-041-D00025 from the KRF. 相似文献
17.
Let X be a smooth complex projective variety with Neron–Severi group isomorphic to ℤ, and D an irreducible divisor with normal crossing singularities. Assume 1<r≤ 3. We prove that if π1(X) doesn't have irreducible PU(r) representations, then π1(X- D) doesn't have irreducible U(r) representations. The proof uses the non-existence of certain stable parabolic bundles. We also obtain a similar result for
GL(2) when D is smooth.
Received: 20 December 1999 / Revised version: 7 May 2000 相似文献
18.
Denis Auroux 《Inventiones Mathematicae》2000,139(3):551-602
We show that every compact symplectic 4-manifold X can be topologically realized as a covering of ℂℙ2 branched along a smooth symplectic curve in X which projects as an immersed curve with cusps in ℂℙ2. Furthermore, the covering map can be chosen to be approximately pseudo-holomorphic with respect to any given almost-complex
structure on X.
Oblatum 9-III-1999 & 2-IX-1999 / Published online: 29 November 1999 相似文献
19.
Soon-Mo Jung 《Bulletin of the Brazilian Mathematical Society》2006,37(3):351-359
Let X be a real Hilbert space with dim X ≥ 2 and let Y be a real normed space which is strictly convex. In this paper, we generalize a theorem of Benz by proving that if a mapping
f, from an open convex subset of X into Y, has a contractive distance ρ and an extensive one Nρ (where N ≥ 2 is a fixed integer), then f is an isometry. 相似文献
20.
J. Brzdęk 《Acta Mathematica Hungarica》2000,87(1-2):147-152
We prove that if X is a real linear normed space and dim X > 1, then, for every isosceles orthogonally exponential mapping f of X into a division ring, either f(X\{0}) = {0} or 0 ∉ f(X). As a consequence of this fact we obtain the following theorem: If X is not an inner product space and dim X > 2, then every isosceles orthogonally exponential mapping of X into a (commutative) field is exponential. We also generalize some results concerning the orthogonally additive mappings.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献