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1.
Jeff Edmonds 《Discrete and Computational Geometry》2008,39(4):747-765
We give a new algorithm for enumerating all possible embeddings of a metric space (i.e., the distances between every pair
within a set of n points) into ℝ2 Cartesian space preserving their l
∞ (or l
1) metric distances. Its expected time is
(i.e., within a poly-log of the size of the input) beating the previous
algorithm. In contrast, we prove that detecting l
∞3 embeddings is NP-complete. The problem is also NP-complete within l
12 or l
∞2 with the added constraint that the locations of two of the points are given or alternatively that the two dimensions are
curved into a three-dimensional sphere. We also refute a compaction theorem by giving a metric space that cannot be embedded
in l
∞3; however, it can be embedded if any single point is removed.
This research is partially supported by NSERC grants. I would like to thank Steven Watson for his extensive help on this paper. 相似文献
2.
V. Yu. Gubarev 《Siberian Mathematical Journal》2009,50(3):395-404
We take the exterior power ℝ4 ∧ ℝ4 of the space ℝ4, its mth symmetric power V = S
m
(∧2ℝ4) = (ℝ4 ∧ ℝ4) ∨ (ℝ4 ∧ ℝ4) ∨ ... ∨(ℝ4 ∧ ℝ4), and put V
0 = L((x ∧ y)∨ ... ∨(x ∧ y): x, y ∈ ℝ4). We find the dimension of V
0 and an algorithm for distinguishing a basis for V
0 efficiently. This problem arose in vector tomography for the purpose of reconstructing the solenoidal part of a symmetric
tensor field.
Original Russian Text Copyright ? 2009 Gubarev V. Yu.
The author was supported by the State Maintenance Program for the Leading Scientific Schools of the Russian Federation (Grant
NSh-344.2008.1).
__________
Novosibirsk. Translated from Sibirskiĭ Matematicheskiĭ Zhurnal, Vol. 50, No. 3, pp. 503–514, May–June, 2009. 相似文献
3.
We prove that if a symmetric submarkovian semigroup (T
t
)
t>0
satisfies an estimate of the form
where ϕ is an increasing C
1
-diffeomorphism of [0,+∞) with subexponential growth, then a suitable function of its infinitesimal generator is bounded from
L
p
(M) to L
q
(M) for 1<p<q<+∞, and that a weak converse holds true if p=2. In the special case where ϕ(t)=Ct
μ
for small t and ϕ(t)=C′ exp(ct
ν
) for large t, μ>0, c>0, 0<ν<1, one obtains a sharp and explicit result, which applies for instance to sublaplacians on solvable unimodular Lie
groups with exponential growth.
Received: 29 June 2001 /
Published online: 1 April 2003
Mathematics Subject Classifications (2000): 47D06, 58J35, 43A80
Research supported by the Italian M.U.R.S.T., fondi 60%, the Italian GNAFA, and the European Commission (European TMR Network
``Harmonic Analysis' 1998–2001, Contract ERBFMRX-CT97-0159). 相似文献
4.
Donald I. Cartwright 《Monatshefte für Mathematik》2001,247(1):93-109
To any locally finite thick building of type there is naturally associated a commutative algebra of operators. When is constructed from a local field F with local ring , and , then is isomorphic to the convolution algebra of compactly supported bi-K-invariant functions on PGL(n+1,F). We give a proof, valid for any , that the multiplicative functionals on may all be expressed in terms of Hall–Littlewood polynomials. Regarding as a subalgebra of the C *-algebra of bounded operators on the space of square summable functions on the vertex set of , we find the spectrum of the C *-algebra , the closure of . This generalizes results obtained in [3] when n = 1 and in [5] when n = 2. 相似文献
5.
We prove Lp-spectral independence for generators of C0-semigroups estimated by the positive C0-semigroup . In the preliminary process of the proof, we obtain the asymptotic expansion formula for the integral kernel of the C0-semigroup . 相似文献
6.
In the present paper, for a boundary value problem with noncoordinated degeneration of the data and a singularity in the solution,
we show that the R
ν
-generalized solution belongs to the weighted space W
2,ν+gb
2+κ+1/κ+2 (Ω, δ)(κ > 0).
Original Russian Text ? V.A. Rukavishnikov, E.V. Kuznetsova, 2009, published in Differentsial’nye Uravneniya, 2009, Vol. 45,
No. 6, pp. 894–898. 相似文献
7.
For fixed generalized reflection matrix P, i.e. P
T
= P, P
2 = I, then matrix X is said to be generalized bisymmetric, if X = X
T
= PXP. In this paper, an iterative method is constructed to find the generalized bisymmetric solutions of the matrix equation A
1
X
1
B
1 + A
2
X
2
B
2 + ⋯ + A
l
X
l
B
l
= C where [X
1,X
2, ⋯ ,X
l
] is real matrices group. By this iterative method, the solvability of the matrix equation can be judged automatically. When
the matrix equation is consistent, for any initial generalized bisymmetric matrix group , a generalized bisymmetric solution group can be obtained within finite iteration steps in the absence of roundoff errors,
and the least norm generalized bisymmetric solution group can be obtained by choosing a special kind of initial generalized
bisymmetric matrix group. In addition, the optimal approximation generalized bisymmetric solution group to a given generalized
bisymmetric matrix group in Frobenius norm can be obtained by finding the least norm generalized bisymmetric solution group of the new matrix equation
, where . Given numerical examples show that the algorithm is efficient.
Research supported by: (1) the National Natural Science Foundation of China (10571047) and (10771058), (2) Natural Science
Foundation of Hunan Province (06JJ2053), (3) Scientific Research Fund of Hunan Provincial Education Department(06A017). 相似文献
8.
9.
For any integersa
1,a
2,a
3,a
4 andc witha
1
a
2
a
3
a
4≢0(modp), this paper shows that there exists a solutionX=(x
1,x
2,x
3,x
4) ∈Z
4 of the congruencea
1
x
1
2
+a
2
x
2
2
+a
3
x
3
2
+a
4
x
4
2
≡c(modp) such that
Research of Zheng Zhiyong is supported by NNSF Grant of China. He would also like to thank the first author and the Mathematics
Department of Kansas, State University for their hospitality and support. 相似文献
10.
Romain Tessera 《Monatshefte für Mathematik》2011,61(4):115-118
The Schur algebra is the algebra of operators which are bounded on ℓ
1 and on ℓ
∞. In this note, we exhibit an element of the group algebra of the free group with two generators, which, as a convolution
operator, is invertible in ℓ
2, and whose inverse is not bounded on ℓ
1 nor on ℓ
∞. In particular, this shows that the Schur algebra is not inverse-closed. 相似文献
11.
张利 《数学年刊A辑(中文版)》2023,44(2):121-132
设B是N维复空间CN中的开单位球,φi为B上的解析自映射,Hα∞表示定义在单位球上的加权解析函数空间.本文主要研究的是从空间Hα∞到Hβ∞上的复合算子线性组合■的紧致性,其中λi(i=1,2,…,M)是非零常数.另外,根据紧致性等价条件,得出算子差分对(Cφ1-Cφ2)-(Cφ3-Cφ1)是紧致的当且仅当Cφ1-Cφ2与Cφ3-Cφ1都是紧致的算子. 相似文献
12.
X. J. Long 《Journal of Optimization Theory and Applications》2011,148(1):197-208
The purpose of this paper is to consider a class of nondifferentiable multiobjective fractional programming problems in which
every component of the objective function contains a term involving the support function of a compact convex set. Based on
the (C,α,ρ,d)-convexity, sufficient optimality conditions and duality results for weakly efficient solutions of the nondifferentiable
multiobjective fractional programming problem are established. The results extend and improve the corresponding results in
the literature. 相似文献
13.
本文首先给出(α,β)-γ开集定义,获得了(α,β)-γ开集性质;然后引入了(α,β)-γ-Ti空间和(α,β)-γ-Ti*空间概念(i=0,1/2,1,2,5/2),并得到它们更广泛的拓扑性质. 相似文献
14.
在一本初等数论的书上,我看到这样一个问题:判断6465+6564是素数还是合数?可以想象这是一个很大的数,需要比较巧的方法才能判定.书上是这样解答的:根据费马小定理,如果a和p互素,p是素数,则ap-1≡1(mod p). 相似文献
15.
基于对广义系统、泛导、泛对称、泛箱原理、泛系相对性提出了新的分析模式与新的相对数学化的简化强化的定义,发展了泛系方法论与泛系相对论的框架与理法,具体内容涉及相对普适的数学化的泛系,200类对偶,对偶转化,泛对称转化,泛系辩证,八畴方法,泛系数学方法,广义量化,逼近转化原则,泛等价定理,供求分析,思维实验,广义灰色系统,等等 相似文献
16.
本文首先利用由两组具有局部最小支集的样条所组成的基函数,构造非均匀2 型三角剖分上二元三次样条空间S31,2(Δmn(2))的若干样条拟插值算子. 这些变差缩减算子由样条函数Bij1支集上5 个网格点或中心和样条函数Bij2支集上5 个网格点处函数值定义. 这些样条拟插值算子具有较好的逼近性,甚至算子Vmn(f) 能保持近最优的三次多项式性. 然后利用连续模,分析样条拟插值算子Vmn(f)一致逼近于充分光滑的实函数. 最后推导误差估计. 相似文献
17.
Grzegorz Lewicki 《Monatshefte für Mathematik》2000,101(1):119-131
In this paper we present an estimate of the relative projection constant for a particular class of subspaces of of codimension two. In some cases the exact value of will be calculated. Also Theorem 2.5 from [11] will be generalized. 相似文献
18.
19.
Yong Zhou 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2009,11(3):191-204
Considering the Navier–Stokes equations in
W ì \mathbbRn\Omega \subset {\mathbb{R}}^n, we prove the asymptotic stability for weak solutions in the marginal class u ∈ C
B
(0, ∞; L
n
) with arbitrary initial and external perturbations. 相似文献
20.
Let K be a field of characteristic 0 and let p, q, G
0
, G
1
, P ∈K[x], deg P ⩾ 1. Further, let the sequence of polynomials (G
n
(x))
n=0
∞ be defined by the second order linear recurring sequence
In this paper we give conditions under which the diophantine equation G
n
(x) = G
m
(P(x)) has at most exp(1018) many solutions (n, m) ε ℤ2, n, m ⩾ 0. The proof uses a very recent result on S-unit equations over fields of characteristic 0 due to Evertse, Schlickewei and Schmidt [14]. Under the same conditions we
present also bounds for the cardinality of the set
In the last part we specialize our results to certain families of orthogonal polynomials.
This work was supported by the Austrian Science Foundation FWF, grant S8307-MAT.
The second author was supported by the Hungarian National Foundation for Scientific Research Grants No 16741 and 38225.
Received June 5, 2001; in revised form February 26, 2002
RID="a"
ID="a" Dedicated to Edmund Hlawka on the occasion of his 85th birthday 相似文献