共查询到20条相似文献,搜索用时 281 毫秒
1.
D. V. Zakharov 《Functional Analysis and Its Applications》2011,45(1):25-32
Using an integrable discrete Dirac operator, we construct a discrete version of the Weierstrass representation for hyperbolic
surfaces parameterized along isotropic directions in ℝ2,1, ℝ3,1, and ℝ2,2. The corresponding discrete surfaces have isotropic edges. We show that any discrete surface satisfying a general monotonicity
condition and having isotropic edges admits such a representation. 相似文献
2.
We define the notion of projective multiresolution analyses, for which, by definition,
the initial space corresponds to a finitely generated projective module over the algebra
C(Tn) of continuous complex-valued functions on an n-torus. The case of ordinary multi-wavelets
is that in which the projective module is actually free. We discuss the properties of projective
multiresolution analyses, including the frames which they provide for L2(n). Then we show how
to construct examples for the case of any diagonal 2 × 2 dilation matrix with integer entries, with
initial module specified to be any fixed finitely generated projective C(T2)-module. We compute
the isomorphism classes of the corresponding wavelet modules. 相似文献
3.
David Kalaj 《Israel Journal of Mathematics》2005,150(1):241-251
We give the new inequality related to the J. C. C. Nitsche conjecture (see [6]). Moreover, we consider the two- and three-dimensional case. LetA(r, 1)={z:r<|z|<1}. Nitsche's conjecture states that if there exists a univalent harmonic mapping from an annulusA(r, 1), to an annulusA(s, 1), thens is at most 2r/(r 2+1).Lyzzaik's result states thats<t wheret is the length of the Grötzsch's ring domain associated withA(r, 1) (see [5]). Weitsman's result states thats≤1/(1+1/2(r logr)2) (see [8]).Our result for two-dimensional space states thats≤1/(1+1/2 log2 r) which improves Weitsman's bound for allr, and Lyzzaik's bound forr close to 1. For three-dimensional space the result states thats≤1/(r?logr). 相似文献
4.
O. V. Shvartsman 《Functional Analysis and Its Applications》2009,43(2):132-139
Let Γ ? U (1, 1) be the subgroup generated by the complex reflections. Suppose that Γ acts discretely on the domain K = {(z 1, z 2) ∈ ?2 ||z 1|2 ? |z 2|2 < 0} and that the projective group PΓ acts on the unit disk B = {|z 1/z 2| < 1} as a Fuchsian group of signature (n 1, ..., n s ), s ? 3, n i ? 2. For such groups, we prove a Chevalley type theorem, i.e., find a necessary and sufficient condition for the quotient space K/Γ to be isomorphic to ?2 ? {0}. 相似文献
6.
Yemon Choi 《Semigroup Forum》2007,75(2):253-271
We show that if L is a semilattice then the ℓ1-convolution algebra of L is biflat precisely when L is "uniformly locally finite". Our proof technique shows in passing
that if this convolution algebra is biflat then it is isomorphic as a Banach algebra to the Banach space ℓ1(L) equipped with pointwise multiplication. At the end we sketch how these techniques may be extended to prove an analogous
characterisation of biflatness for Clifford semigroup algebras. 相似文献
7.
Emily J. King Maria A. Skopina 《P-Adic Numbers, Ultrametric Analysis, and Applications》2010,2(3):222-231
With an eye on applications in quantum mechanics and other areas of science, much work has been done to generalize traditional
analytic methods to p-adic systems. In 2002 the first paper on p-adic wavelets was published. Since then p-adic wavelet sets, multiresolution analyses, and wavelet frames have all been introduced. However, so far all constructions
have involved dilations by p. This paper presents the first construction of a p-adic wavelet system with a more general matrix dilation, laying the foundation for further work in this direction. 相似文献
8.
Dimitra Kosta 《Proceedings of the Steklov Institute of Mathematics》2009,264(1):102-109
Let X be a complete intersection of two hypersurfaces F
n
and F
k
in ℙ5 of degree n and k, respectively, with n ≥ k, such that the singularities of X are nodal and F
k
is smooth. We prove that if the threefold X has at most (n + k − 2)(n − 1) − 1 singular points, then it is factorial. 相似文献
9.
10.
Let E be an equivalence relation on the powerset of an uncountable set, which is reasonably definable. We assume that any two subsets with symmetric difference of size exactly 1 are not equivalent. We investigate whether for E there are many pairwise non equivalent sets.
I would like to thank Alice Leonhardt for the beautiful typing.This research was supported by The Israel Science Foundation. Publication 724.
Mathematics Subject Classification (2000): 03E47, 03E35; 20K20, 20K35 相似文献
11.
A key tool in recent advances in understanding arithmetic progressions and other patterns in subsets of the integers is certain
norms or seminorms. One example is the norms on ℤ/Nℤ introduced by Gowers in his proof of Szemerédi’s Theorem, used to detect uniformity of subsets of the integers. Another
example is the seminorms on bounded functions in a measure preserving system (associated to the averages in Furstenberg’s
proof of Szemerédi’s Theorem) defined by the authors. For each integer k ≥ 1, we define seminorms on ℓ∞(ℤ) analogous to these norms and seminorms. We study the correlation of these norms with certain algebraically defined sequences,
which arise from evaluating a continuous function on the homogeneous space of a nilpotent Lie group on a orbit (the nilsequences).
Using these seminorms, we define a dual norm that acts as an upper bound for the correlation of a bounded sequence with a
nilsequence. We also prove an inverse theorem for the seminorms, showing how a bounded sequence correlates with a nilsequence.
As applications, we derive several ergodic theoretic results, including a nilsequence version of the Wiener-Wintner ergodic
theorem, a nil version of a corollary to the spectral theorem, and a weighted multiple ergodic convergence theorem. 相似文献
12.
Let ƒ and g be real-analytic functions near the origin in ℝ2. Given 1 < p < ∞, we obtain a characterization of the set of positive numbers ∈ and δ that ensures
for some small neighborhood K of the origin. A notion of stability is introduced in relation to Ap weights and a counterexample is presented to show that the two-dimensional weighted problem, unlike its analog in dimension
one, is not stable. 相似文献
13.
Erlend Fornæss Wold 《Arkiv f?r Matematik》2010,48(1):207-210
We construct a 2-dimensional complex manifold X which is the increasing union of proper subdomains that are biholomorphic to ℂ2, but X is not Stein. 相似文献
14.
Associated to a projective arrangement of hyperplanes
${\mathcal A}$
n
is the module D$({\mathcal A})$,
which consists of derivations tangent to
${\mathcal A}$. We study D$({\mathcal A})$
when ${\mathcal A}$ is a configuration of lines in
2.
In this setting, we relate the deletion/restriction construction used in
the study of hyperplane arrangements to elementary modifications of bundles.
This allows us to obtain bounds on the Castelnuovo-Mumford regularity of
D$({\mathcal A})$. We
also give simple combinatorial conditions for the associated bundle to be
stable, and describe its jump lines. These regularity bounds and stability
considerations impose constraints on Teraos conjecture. 相似文献
15.
V. I. Berdyshev 《Proceedings of the Steklov Institute of Mathematics》2017,297(1):27-34
In the problem of tracking an object moving in ?3 by observers, the most concealed trajectory is characterized under the condition that the object is at any time visible to at most two observers. 相似文献
16.
We classify all surfaces in ℍ2 × ℝ for which the unit normal makes a constant angle with the ℝ-direction. Here ℍ2 is the hyperbolic plane.
The author was supported by grants CEEX ET 5883/2006-2008 and PNII ID_ 398/2007-2010 ANCS (Romania). 相似文献
17.
In this paper, we present the conditions on dilation parameter {s
j}j that ensure a discrete irregular wavelet system {s
j
n/2ψ(s
j
·−bk)}
j∈ℤ,k∈ℤ
n
to be a frame on L2(ℝn), and for the wavelet frame we consider the perturbations of translation parameter b and frame function ψ respectively. 相似文献
18.
The partial ordering of Medvedev reducibility restricted to the family of 01 classes is shown to be dense. For two disjoint computably enumerable sets, the class of separating sets is an important example of a 01 class, which we call a ``c.e. separating class'. We show that there are no non-trivial meets for c.e. separating classes, but that the density theorem holds in the sublattice generated by the c.e. separating classes.
Mathematics Subject Classification (2000): 03D30, 03D25 相似文献
19.
We determine all tight Lagrangian surfaces in S
2 × S
2. In particular, globally tight Lagrangian surfaces in S
2 × S
2 are nothing but real forms of this symmetric space. 相似文献
20.
Linda Brown Westrick 《Israel Journal of Mathematics》2017,219(1):431-448
A family of sets is union-free if there are no three distinct sets in the family such that the union of two of the sets is equal to the third set. Kleitman proved that every union-free family has size at most (1+o(1))( n/2 n ). Later, Burosch–Demetrovics–Katona–Kleitman–Sapozhenko asked for the number α(n) of such families, and they proved that \({2^{\left( {\begin{array}{*{20}{c}} n \\ {n/2} \end{array}} \right)}} \leqslant \alpha \left( n \right) \leqslant {2^{2\sqrt 2 \left( {\begin{array}{*{20}{c}} n \\ {n/2} \end{array}} \right)\left( {1 + o\left( 1 \right)} \right)}}\) They conjectured that the constant \(2\sqrt 2 \) can be removed in the exponent of the right-hand side. We prove their conjecture by formulating a new container-type theorem for rooted hypergraphs. 相似文献