共查询到20条相似文献,搜索用时 46 毫秒
1.
Christine Bachoc Renaud Coulangeon Gabriele Nebe 《Journal of Algebraic Combinatorics》2002,16(1):5-19
We introduce the notion of a t-design on the Grassmann manifold
of the m-subspaces of the Euclidean space
n
. It generalizes the notion of antipodal spherical design which was introduced by P. Delsarte, J.-M. Goethals and J.-J. Seidel. We characterize the finite subgroups of the orthogonal group which have the property that all its orbits are t-designs. Generalizing a result due to B. Venkov, we prove that, if the minimal m-sections of a lattice L form a 4-design, then L is a local maximum for the Rankin function
n,m
. 相似文献
2.
Shiquan WU 《应用数学学报(英文版)》1996,12(4):377-383
Letn, s
1,s
2, ... ands
n
be positive integers. Assume
is an integer for eachi}. For
,
, and
, denotes
p
(a)={j|1jn,a
j
p},
, and
.
is called anI
t
p
-intersecting family if, for any a,b
,a
i
b
i
=min(a
i
,b
i
)p for at leastt i's.
is called a greedyI
t
P
-intersecting family if
is anI
t
p
-intersecting family andW
p
(A)W
p
(B+A
c
) for anyAS
p
(
) and any
with |B|=t–1.In this paper, we obtain a sharp upper bound of |
| for greedyI
t
p
-intersecting families in
for the case 2ps
i
(1in) ands
1>s
2>...>s
n
.This project is partially supported by the National Natural Science Foundation of China (No.19401008) and by Postdoctoral Science Foundation of China. 相似文献
3.
We study the problem of representation of a homogeneous semigroup {
t
}
t 0 of transformations of probability measures on
in the form
where
satisfies a differential equation of a special form dependent on the measure . We give necessary and sufficient conditions for this representation. 相似文献
4.
Arnold Neumaier 《Geometriae Dedicata》1982,12(4):351-366
It is proved that a quasi-residual 2-(v, k, )-design with k>1/25+O(4) can be embedded into a symmetric 2-design. This improves a result by Bose, Shrikhande, and Singhi [1]. Our proof uses properties of strongly regular multigraphs and
-designs. In particular, we give a simple sufficient condition for a strongly regular multigraph to be isomorphic to the block multigraph of a 2-design.Part of this research was done while the author was at Westfield College, London. 相似文献
5.
Koen Thas 《Designs, Codes and Cryptography》2002,25(3):247-253
Suppose
is a generalized quadrangle (GQ) of order
, with a regular point. Then there is a net which arises from this regular point. We prove that if such a net has a proper subnet with the same degree as the net, then it must be an affine plane of order t. Also, this affine plane induces a proper subquadrangle of order t containing the regular point, and we necessarily have that
. This result has many applications, of which we give one example. Suppose
is an elation generalized quadrangle (EGQ) of order
, with elation point p. Then
is called a skew translation generalized quadrangle (STGQ) with base-point p if there is a full group of symmetries about p of order t which is contained in the elation group. We show that a GQ
of order s is an STGQ with base-point p if and only if p is an elation point which is regular. 相似文献
6.
Charles J. Colbourn Dean G. Hoffman Kevin T. Phelps Vojtěch Rödl Peter M. Winkler 《Combinatorica》1991,11(3):207-218
We prove that the number oft-wise balanced designs of ordern is asymptotically
, provided that blocks of sizet are permitted. In the process, we prove that the number oft-profiles (multisets of block sizes) is bounded below by
and above by
for constants c2>c1>0. 相似文献
7.
We give a pointwise estimate of meromorphic solutions of linear
differential equations with coefficients meromorphic in a finite
disk or in the open plane. Our results improve some earlier
estimates of Bank and Laine. In particular we show that the
growth of meromorphic solutions with
()>0 can be
estimated in terms of initial conditions of the solution at or
near the origin and the characteristic functions of the
coefficients. Examples show that the estimates are sharp in a
certain sense. Our results give an affirmative answer to a
question of Milne Anderson.
Our method consists of two steps. In Theorem 2.1 we construct a
path (0, ,
t) consisting of the ray
followed by the circle
on which the coefficients are all bounded in terms of the sum of
their characteristic functions on a larger circle. In Theorem 2.2
we show how such an estimate for the coefficients leads to a
corresponding bound for the solution on z = t.
Putting these two steps together we obtain our main result, Theorem 2.3. 相似文献
8.
Laurel L. Carpenter 《Designs, Codes and Cryptography》1996,9(1):51-59
Given any protective plane of even order q containing a hyperoval
, a Steiner
design can be constructed. The 2-rank of this design is bounded above by rank2() – q – 1. Using a result of Blokhuis and Moorhouse [3], we show that this bound is met when is desarguesian and
is regular. We also show that the block graph of the Steiner 2-design in this case produces a Hadamard design which is such that the binary code of the associated 3-design contains a copy of the first-order Reed-Muller code of length 22m
, where q = 2
m
. 相似文献
9.
P. V. Semenov 《Functional Analysis and Its Applications》2002,36(2):159-161
A fixed-point theorem is proved for a broad class of closed-valued
-contractions with
for any positive t and with
. 相似文献
10.
James Murdock Lih -Chyun Wang 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1996,47(5):760-789
For a class of nonlinear oscillation problems containing a small parameter, it is known that a two-scale method using timest and t gives results valid to any desired order for time
(1/). We ask when results can be obtained which are valid for
(1/2) or for allt > 0. We show that there is an obstruction to introducing a third time scale 2
t, and give an example in which this obstruction does not vanish, so that a third scale cannot be introduced, even though the solution exists for all time. The obstruction does vanish if the first order averaged equation vanishes, in which case the three-scale solution actually involves onlyt and 2
t and is valid for time
(1/2). The obstruction also vanishes if a certain contracting or dissipative condition is met, but in this case the two-scale solution is already valid for all time and the third scale is not needed. These results correspond to known results for the method of averaging, but are here proved for the multiple scale method without use of averaging. 相似文献
11.
Amnon Neeman 《K-Theory》2001,22(1-2):1-144
Let
be a triangulated category, and assume it admits at least one model. In this article, we define a K-theory for
. The main theorem is that, given any bounded i-structure on
, the K-theory of the heart agrees with the K-theory of
. An immediate consequence tells us that, if two Abelian categories occur as hearts of a triangulated category for two different t-structures, then their K-theories must be isomorphic.The proof was also sketched in previous articles in this series. The virtue of this article is in the careful detail in which it is written down. 相似文献
12.
E. B. Dynkin 《Probability Theory and Related Fields》1993,94(3):399-411
Summary We consider Markov processes with a fixed transition functionp(r, x; t, B) and with random birth times. We show that a process
can be obtained from (X
t
,P) by birth delay if and only if
for allt andB. As an application, we give a new version and a new proof of the results of Rost [R] and Fitzsimmons [F2] on stopping distributions of Markov processes. The key Lemma 1.1 replaces the filling scheme used by the previous authors.Birth delay was considered from a different prospective in [F1].Partially supported by the National Science Foundation Grant DMS-8802667 相似文献
13.
Real valued M-estimators
in a statistical model 1 with observations
are replaced by
-valued M-estimators
in a new model with observations
where
are regressors,
is a structural parameter and
a structural function of the new model. Sufficient conditions for the consistency of
are derived, motivated by the sufficiency conditions for the simpler parent estimator
The result is a general method of consistent estimation in a class of nonlinear (pseudolinear) statistical problems. If F
has a natural exponential density ex–b( x ) then our pseudolinear model with u = (g o )–1 reduces to the well known generalized linear model, provided () = db()/d and g is the so-called link function of the generalized linear model. General results are illustrated for special pairs and leading to some classical M-estimators of mathematical statistics, as well as to a new class of generalized -quantile estimators. 相似文献
14.
Jiří Močkoř 《Czechoslovak Mathematical Journal》2002,52(3):595-607
For an order embedding
of a partly ordered group G into an l-group a topology is introduced on which is defined by a family of valuations W on G. Some density properties of sets h(G), h(X
t
) and
(X
t
being t-ideals in G) in the topological space are then investigated, each of them being equivalent to the statement that h is a strong theory of quasi-divisors. 相似文献
15.
Mervyn J. Silvapulle Pranab K. Sen 《Annals of the Institute of Statistical Mathematics》1993,45(1):159-171
Consider the linear modelY=X+E in the usual matrix notation where the errors are independent and identically distributed. We develop robust tests for a large class of one- and two-sided hypotheses about when the data are obtained and tests are carried out according to a group sequential design. To illustrate the nature of the main results, let
and
be anM- and the least squares estimator of respectively which are asymptotically normal about with covariance matrices 2(X
t
X)–1 and 2(X
t
X)–1 respectively. Let the Wald-type statistics based on
and
be denoted byRW andW respectively. It is shown thatRW andW have the same asymptotic null distributions; here the limit is taken with the number of groups fixed but the numbers of observations in the groups increase proportionately. Our main result is that the asymptotic Pitman efficiency ofRW relative toW is (2/2). Thus, the asymptotic efficiency-robustness properties of
relative to
translate to asymptotic power-robustness ofRW relative toW. Clearly, this is an attractive result since we already have a large literature which shows that
is efficiency-robust compared to
. The results of a simulation study show that with realistic sample sizes,RW is likely to have almost as much power asW for normal errors, and substantially more power if the errors have long tails. The simulation results also illustrate the advantages of group sequential designs compared to a fixed sample design, in terms of sample size requirements to achieve a specified power. 相似文献
16.
In this paper we consider a system whose state
x changes to (x) if a perturbation occurs at the time
t, for
. Moreover, the state
x changes to the new state
(x) at time
t, for
. It is assumed that the
number of perturbations in an interval (0,
t) is a Poisson process. Here
and are measurable maps from a measure space
into itself. We give
conditions for the existence of a stationary distribution of the
system when the maps and commute, and we prove that any
stationary distribution is an invariant measure of these
maps. 相似文献
17.
Let L(Q
t
) denote the number of linear extensions of the t-dimensional Boolean lattice Q
t
. We use the entropy method of Kahn to show that
where the logarithms are base 2. We also find the exact maximum number of linear extensions of a d-regular bipartite order on n elements, in the case when n is a multiple of 2d. 相似文献
18.
In this paper, we consider several constructions which from a given B-product *
B
lead to another one
We shall be interested in finding what algebraic properties of the ring
are shared also by the ring
. In particular, for some constructions the rings R
B and
will be isomorphic and therefore have the same algebraic properties. 相似文献
19.
By removing the components of at-spread
of a finite projective spacePG(d, q) from each hyperplane ofPG(d, q), the blocks of a regular group divisible design
are obtained We characterize geometrict-spreads as thoset-spreads
which are such that the dual of
is also a group divisible design. 相似文献
20.
Albrecht Beutelspacher 《Geometriae Dedicata》1980,9(4):425-449
A t-blocking set in the finite projective space PG(d, q) with dt+1 is a set
of points such that any (d–t)-dimensional subspace is incident with a point of
and no t-dimensional subspace is contained in
. It is shown that |
|q
t
+...+1+q
t–1q and the examples of minimal cardinality are characterized. Using this result it is possible to prove upper and lower bounds for the cardinality of partial t-spreads in PG(d, q). Finally, examples of blocking sets and maximal partial spreads are given. 相似文献