共查询到20条相似文献,搜索用时 31 毫秒
1.
David Paget 《Journal of Approximation Theory》1988,54(3)
Let f ε Cn+1[−1, 1] and let H[f](x) be the nth degree weighted least squares polynomial approximation to f with respect to the orthonormal polynomials qk associated with a distribution dα on [−1, 1]. It is shown that if qn+1/qn max(qn+1(1)/qn(1), −qn+1(−1)/qn(−1)), then f − H[f] fn + 1 · qn+1/qn + 1(n + 1), where · denotes the supremum norm. Furthermore, it is shown that in the case of Jacobi polynomials with distribution (1 − t)α (1 + t)β dt, α, β > −1, the condition on qn+1/qn is satisfied when either max(α,β) −1/2 or −1 < α = β < −1/2. 相似文献
2.
In this paper new lower bounds for the cardinality of minimal m-blocking sets are determined. Let r2(q) be the number such that q+r2(q)+1 is the cardinality of the smallest non-trivial line-blocking set in a plane of order q. If B is a minimal m-blocking set in PG(n,q) that contains at most qm+qm−1+…+q+1+r2(q)·(∑i=2m−n′m−1qi) points for an integer n′ satisfying mn′2m, then the dimension of B is at most n′. If the dimension of B is n′, then the following holds. The cardinality of B equals qm+qm−1+…+q+1+r2(q)(∑i=2m−n′m−1qi). For n′=m the set B is an m-dimensional subspace and for n′=m+1 the set B is a cone with an (m−2)-dimensional vertex over a non-trivial line-blocking set of cardinality q+r2(q)+1 in a plane skew to the vertex. This result is due to Heim (Mitt. Math. Semin. Giessen 226 (1996), 4–82). For n′>m+1 and q not a prime the number q is a square and for q16 the set B is a Baer cone. If q is odd and |B|<qm+qm−1+…+q+1+r2(q)(qm−1+qm−2), it follows from this result that the subspace generated by B has dimension at most m+1. Furthermore we prove that in this case, if
, then B is an m-dimensional subspace or a cone with an (m−2)-dimensional vertex over a non-trivial line-blocking set of cardinality q+r2(q)+1 in a plane skew to the vertex. For q=p3h, p7 and q not a square we show this assertion for |B|qm+qm−1+…+q+1+q2/3·(qm−1+…+1). 相似文献
3.
A mixed partition of PG(2n−1,q2) is a partition of the points of PG(2n−1,q2) into (n−1)-spaces and Baer subspaces of dimension 2n−1. In (Bruck and Bose, J. Algebra 1 (1964) 85) it is shown that such a mixed partition of PG(2n−1,q2) can be used to construct a (2n−1)-spread of PG(4n−1,q) and hence a translation plane of order q2n. In this paper, we provide several new examples of such mixed partitions in the case when n=2. 相似文献
4.
The rank of a q-ary code C is the dimension of the subspace spanned by C. The kernel of a q-ary code C of length n can be defined as the set of all translations leaving C invariant. Some relations between the rank and the dimension of the kernel of q-ary 1-perfect codes, over
as well as over the prime field
, are established. Q-ary 1-perfect codes of length n=(qm − 1)/(q − 1) with different kernel dimensions using switching constructions are constructed and some upper and lower bounds for the dimension of the kernel, once the rank is given, are established.Communicated by: I.F. Blake 相似文献
5.
Amit Deshpande Rahul Jain T. Kavitha Satyanarayana V. Lokam Jaikumar Radhakrishnan 《Random Structures and Algorithms》2005,27(3):358-378
An error‐correcting code is said to be locally decodable if a randomized algorithm can recover any single bit of a message by reading only a small number of symbols of a possibly corrupted encoding of the message. Katz and Trevisan 12 showed that any such code C : {0, 1}n → Σm with a decoding algorithm that makes at most q probes must satisfy m = Ω((n/log |Σ|)q/(q?1)). They assumed that the decoding algorithm is non‐adaptive, and left open the question of proving similar bounds for adaptive decoders. We show m = Ω((n/log |Σ|)q/(q?1)) without assuming that the decoder is nonadaptive. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2005 相似文献
6.
Generalized Hadamard matrices of order qn−1 (q—a prime power, n2) over GF(q) are related to symmetric nets in affine 2-(qn,qn−1,(qn−1−1)/(q−1)) designs invariant under an elementary abelian group of order q acting semi-regularly on points and blocks. The rank of any such matrix over GF(q) is greater than or equal to n−1. It is proved that a matrix of minimum q-rank is unique up to a monomial equivalence, and the related symmetric net is a classical net in the n-dimensional affine geometry AG(n,q). 相似文献
7.
Let
and
be two intersecting families of k-subsets of an n-element set. It is proven that |
| ≤ (k−1n−1) + (k−1n−1) holds for
, and equality holds only if there exist two points a, b such that {a, b} ∩ F ≠ for all F
. For
an example showing that in this case max |
| = (1−o(1))(kn) is given. This disproves an old conjecture of Erdös [7]. In the second part we deal with several generalizations of Kneser's conjecture. 相似文献
8.
G. L. Ebert (1985) constructed (qn + 1)-caps in PG(2n − 1, q), n even, which were the orbits of the subgroup of order qn + 1 of a cyclic Singer group of PG(2n − 1, q). This article shows that these caps are the intersection of n − 1 linearly independent elliptic quadrics of PG(2n − 1, q). 相似文献
9.
We prove that there does not exist a [q4+q3−q2−3q−1, 5, q4−2q2−2q+1]q code over the finite field
for q≥ 5. Using this, we prove that there does not exist a [gq(5, d), 5, d]q code with q4 −2q2 −2q +1 ≤ d ≤ q4 −2q2 −q for q≥ 5, where gq(k,d) denotes the Griesmer bound.MSC 2000: 94B65, 94B05, 51E20, 05B25 相似文献
10.
Let n and k be positive integers. Let Cq be a cyclic group of order q. A cyclic difference packing (covering) array, or a CDPA(k, n; q) (CDCA(k, n; q)), is a k × n array (aij) with entries aij (0 ≤ i ≤ k−1, 0 ≤ j ≤ n−1) from Cq such that, for any two rows t and h (0 ≤ t < h ≤ k−1), every element of Cq occurs in the difference list
at most (at least) once. When q is even, then n ≤ q−1 if a CDPA(k, n; q) with k ≥ 3 exists, and n ≥ q+1 if a CDCA(k, n; q) with k ≥ 3 exists. It is proved that a CDCA(4, q+1; q) exists for any even positive integers, and so does a CDPA(4, q−1; q) or a CDPA(4, q−2; q). The result is established, for the most part, by means of a result on cyclic difference matrices with one hole, which is of interest in its own right. 相似文献
11.
Let X1,…, Xn be i.i.d. random variables symmetric about zero. Let Ri(t) be the rank of |Xi − tn−1/2| among |X1 − tn−1/2|,…, |Xn − tn−1/2| and Tn(t) = Σi = 1nφ((n + 1)−1Ri(t))sign(Xi − tn−1/2). We show that there exists a sequence of random variables Vn such that sup0 ≤ t ≤ 1 |Tn(t) − Tn(0) − tVn| → 0 in probability, as n → ∞. Vn is asymptotically normal. 相似文献
12.
In this paper, we discuss properties of the ω,q-Bernstein polynomials introduced by S. Lewanowicz and P. Woźny in [S. Lewanowicz, P. Woźny, Generalized Bernstein polynomials, BIT 44 (1) (2004) 63–78], where fC[0,1], ω,q>0, ω≠1,q−1,…,q−n+1. When ω=0, we recover the q-Bernstein polynomials introduced by [G.M. Phillips, Bernstein polynomials based on the q-integers, Ann. Numer. Math. 4 (1997) 511–518]; when q=1, we recover the classical Bernstein polynomials. We compute the second moment of , and demonstrate that if f is convex and ω,q(0,1) or (1,∞), then are monotonically decreasing in n for all x[0,1]. We prove that for ω(0,1), qn(0,1], the sequence converges to f uniformly on [0,1] for each fC[0,1] if and only if limn→∞qn=1. For fixed ω,q(0,1), we prove that the sequence converges for each fC[0,1] and obtain the estimates for the rate of convergence of by the modulus of continuity of f, and the estimates are sharp in the sense of order for Lipschitz continuous functions. 相似文献
13.
Sergey V. Avgustinovich Olof Heden Faina I. Solov’eva 《Designs, Codes and Cryptography》2006,39(3):317-322
The main result is that to any even integer q in the interval 0 ≤ q ≤ 2n+1-2log(n+1), there are two perfect codes C1 and C2 of length n = 2m − 1, m ≥ 4, such that |C1 ∩ C2| = q. 相似文献
14.
Extending MDS Codes 总被引:1,自引:0,他引:1
T. L. Alderson 《Annals of Combinatorics》2005,9(2):125-135
A q-ary (n, k)-MDS code, linear or not, satisfies n ≤ q + k − 1. A code meeting this bound is said to have maximum length. Using purely combinatorial methods we show that an MDS code with n = q + k − 2 can be uniquely extended to a maximum length code if and only if q is even. This result is best possible in the sense that there is, for example, a non-extendable 4-ary (5, 4)-MDS code. It may be that the proof of our result is as interesting as the result itself. We provide a simple necessary and sufficient condition
for code extendability. In future work, this condition might be suitably modified to give an extendability condition for arbitrary (shorter) MDS codes.Received December 1, 2003 相似文献
15.
Let {Xn} be a strictly stationary φ-mixing process with Σj=1∞ φ1/2(j) < ∞. It is shown in the paper that if X1 is uniformly distributed on the unit interval, then, for any t [0, 1], |Fn−1(t) − t + Fn(t) − t| = O(n−3/4(log log n)3/4) a.s. and sup0≤t≤1 |Fn−1(t) − t + Fn(t) − t| = (O(n−3/4(log n)1/2(log log n)1/4) a.s., where Fn and Fn−1(t) denote the sample distribution function and tth sample quantile, respectively. In case {Xn} is strong mixing with exponentially decaying mixing coefficients, it is shown that, for any t [0, 1], |Fn−1(t) − t + Fn(t) − t| = O(n−3/4(log n)1/2(log log n)3/4) a.s. and sup0≤t≤1 |Fn−1(t) − t + Fn(t) − t| = O(n−3/4(log n)(log log n)1/4) a.s. The results are further extended to general distributions, including some nonregular cases, when the underlying distribution function is not differentiable. The results for φ-mixing processes give the sharpest possible orders in view of the corresponding results of Kiefer for independent random variables. 相似文献
16.
Let Bn( f,q;x), n=1,2,… be q-Bernstein polynomials of a function f : [0,1]→C. The polynomials Bn( f,1;x) are classical Bernstein polynomials. For q≠1 the properties of q-Bernstein polynomials differ essentially from those in the classical case. This paper deals with approximating properties of q-Bernstein polynomials in the case q>1 with respect to both n and q. Some estimates on the rate of convergence are given. In particular, it is proved that for a function f analytic in {z: |z|<q+} the rate of convergence of {Bn( f,q;x)} to f(x) in the norm of C[0,1] has the order q−n (versus 1/n for the classical Bernstein polynomials). Also iterates of q-Bernstein polynomials {Bnjn( f,q;x)}, where both n→∞ and jn→∞, are studied. It is shown that for q(0,1) the asymptotic behavior of such iterates is quite different from the classical case. In particular, the limit does not depend on the rate of jn→∞. 相似文献
17.
Joseph E. Bonin 《Advances in Applied Mathematics》1996,17(4):460-476
It is known that a geometry with rankrand no minor isomorphic to the (q+2)-point line has at most (qr−1)/(q−1) points, with strictly fewer points ifr>3 andqis not a prime power. Forqnot a prime power andr>3, we show thatqr−1−1 is an upper bound. Forqa prime power andr>3, we show that any rank-rgeometry with at leastqr−1points and no (q+2)-point-line minor is representable overGF(q). We strengthen these bounds toqr−1−(qr−2−1)/(q−1)−1 andqr−1−(qr−2−1)/(q−1) respectively whenqis odd. We give an application to unique representability and a new proof of Tutte's theorem: A matroid is binary if and only if the 4-point line is not a minor. 相似文献
18.
Leszek Plaskota 《Journal of Approximation Theory》1998,93(3):501-515
We consider the average caseL∞-approximation of functions fromCr([0, 1]) with respect to ther-fold Wiener measure. An approximation is based onnfunction evaluations in the presence of Gaussian noise with varianceσ2>0. We show that the n th minimal average error is of ordern−(2r+1)/(4r+4) ln1/2 n, and that it can be attained either by the piecewise polynomial approximation using repetitive observations, or by the smoothing spline approximation using non-repetitive observations. This completes the already known results forLq-approximation withq<∞ andσ0, and forL∞-approximation withσ=0. 相似文献
19.
Kantorovich gave an upper bound to the product of two quadratic forms, (X′AX) (X′A−1X), where X is an n-vector of unit length and A is a positive definite matrix. Bloomfield, Watson and Knott found the bound for the product of determinants |X′AX| |X′A−1X| where X is n × k matrix such that X′X = Ik. In this paper we determine the bounds for the traces and determinants of matrices of the type X′AYY′A−1X, X′B2X(X′BCX)−1 X′C2X(X′BCX)−1 where X and Y are n × k matrices such that X′X = Y′Y = Ik and A, B, C are given matrices satisfying some conditions. The results are applied to the least squares theory of estimation. 相似文献
20.
V. V. Yablokov 《Journal of Mathematical Sciences》2005,129(1):3680-3687
We consider the problem of the averaging of solutions to the Laplace operator in domains with narrow slanting channels of length O(εq), q = const > 0, and diameter a
ε = o(ε q), where ε is a small parameter. The number of channels is N
ε = O (ε 1−n
), where n is the dimension of the space. We study the asymptotic behavior of solutions, obtain the limit problem, and estimate the closeness of the initial and limit problem.__________Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 10, Suzdal Conference-4, 2003. 相似文献