共查询到20条相似文献,搜索用时 31 毫秒
2.
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
3.
4.
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
5.
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
6.
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
7.
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.
S. Yu. Podzorov 《Algebra and Logic》2005,44(2):82-94
We deal in specific features of the algebraic structure of Rogers semilattices of n
0-computable numberings, for n 2. It is proved that any Lachlan semilattice is embeddable (as an ideal) in such every semilattice, and that over an arbitrary non 0-principal element of such a lattice, any Lachlan semilattice is embeddable (as an interval) in it.Supported by INTAS grant No. 00-499, by FP Universities of Russia grant UR.04.01.013, and by the Grant Center for Fundamental Research (GCFR), project PD02-1.1-475.__________Translated from Algebra i Logika, Vol. 44, No. 2, pp. 148–172, March–April, 2005. 相似文献
10.
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
11.
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
12.
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
13.
We use a distortion to define the dual complex of a cubical subdivision of ℝ
n
as an n-dimensional subcomplex of the nerve of the set of n-cubes. Motivated by the topological analysis of high-dimensional digital image data, we consider such subdivisions defined
by generalizations of quad- and oct-trees to n dimensions. Assuming the subdivision is balanced, we show that mapping each vertex to the center of the corresponding n-cube gives a geometric realization of the dual complex in ℝ
n
. 相似文献
14.
Studying computable representations of projective planes, for the classes K of pappian, desarguesian, and all projective planes, we prove that K c /? admits no hyperarithmetical Friedberg enumeration and admits a Friedberg Δ0α+3-computable enumeration up to a Δ0 α -computable isomorphism. 相似文献
15.
Juan A. Aledo José M. Espinar José A. Gálvez 《Calculus of Variations and Partial Differential Equations》2007,29(3):347-363
We study isometric immersions of surfaces of constant curvature into the homogeneous spaces and . In particular, we prove that there exists a unique isometric immersion from the standard 2-sphere of constant curvature
c > 0 into and a unique one into when c > 1, up to isometries of the ambient space. Moreover, we show that the hyperbolic plane of constant curvature c < −1 cannot be isometrically immersed into or .
J.A. Aledo was partially supported by Ministerio de Education y Ciencia Grant No. MTM2004-02746 and Junta de Comunidades de
Castilla-La Mancha, grant no. PAI-05-034.
J.M. Espinar and J.A. Gálvez were partially supported by Ministerio de Education y Ciencia grant no. MTM2004-02746 and Junta
de Andalucía Grant No. FQM325. 相似文献
16.
Let w and M be the countable distributive lattices of Muchnik and Medvedev degrees of non-empty 10 subsets of 2, under Muchnik and Medvedev reducibility, respectively. We show that all countable distributive lattices are lattice-embeddable below any non-zero element of w. We show that many countable distributive lattices are lattice-embeddable below any non-zero element of M.Simpsons research was partially supported by NSF Grant DMS-0070718. We thank the anonymous referee for a careful reading of this paper and helpful comments. 相似文献
17.
Ralph R. Gomez 《Geometriae Dedicata》2011,150(1):249-255
We settle completely an open problem formulated by Boyer and Galicki in [5] which asks whether or not #kS 2 × S 3 are negative Sasakian manifolds for all k. As a consequence of the affirmative answer to this problem, there exists so-called Sasaki η-Einstein and Lorentzian Sasaki-Einstein metrics on these five-manifolds for all k and moreover all of these can be realized as links of isolated hypersurface singularities defined by weighted homogenous polynomials. The key step is to construct infinitely many hypersurfaces in weighted projective space that contain branch divisors \({\Delta=\sum_{i}\left(1-\frac{1}{m_{i}}\right)D_i}\) such that the D i are rational curves. 相似文献
18.
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
19.
20.
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