共查询到20条相似文献，搜索用时 31 毫秒
1.
D. Junghenn 《Semigroup Forum》2008,66(2):328-336
Abstract. Let
be a semidirect product of semitopological semigroups S and T . If S and T act on topological spaces X and Y , respectively, then under suitable conditions there is a natural action of
on X × Y . In this paper we characterize the almost periodic and strongly almost periodic compactification of the flow
,
in terms of related compactifications of (S,X) and (T,Y) . 相似文献
2.
Lewin 《Semigroup Forum》2008,66(1):43-62
Abstract. Given a set A and a function
, we study the set of all functions
that are continuous for all topologies for which f continuous.
We prove that in a sense to be made precise in the text, for any essentially infinitary function f , any non-constant such g equals f
n
, for some n∈ N. We also prove a similar result for the clone of n -ary functions from
. 相似文献
3.
Micciancio 《Discrete and Computational Geometry》2003,29(1):133-138
Abstract. We prove that the best way to reduce the volume of the n -dimensional unit cube by a linear transformation that maps each of the main vertices
to a point within distance ɛ <
from
is to shorten all edges by a factor (1-ɛ) . In particular, the minimal volume of such an almost cubic parallelepiped is (1-ɛ)
n
. This problem naturally arises in the construction of lattice-based one-way functions with worst-case/ average-case connection. 相似文献
4.
Abstract. Subdivision with finitely supported masks is an efficient method to create discrete multiscale representations of smooth
surfaces for CAGD applications. Recently a new subdivision scheme for triangular meshes, called
-subdivision , has been studied. In comparison to dyadic subdivision, which is based on the dilation matrix 2I ,
-subdivision is based on a dilation M with det M=3 . This has certain advantages, for example, a slower growth for the number of control points.
This paper concerns the problem of achieving maximal sum rule orders for stationary
-subdivision schemes with given mask support, which is important because the sum rule order characterizes the order of the
polynomial reproduction, and provides an upper bound on the Sobolev smoothness of the surface. We study both interpolating
and approximating schemes for a natural family of symmetric mask support sets related to squares of sidelength 2n in Z
2
, and obtain exact formulas for the maximal sum rule order for arbitrary n . For approximating schemes, the solution is simple, and schemes with maximal sum rule order are realized by an explicit
family of schemes based on repeated averaging [15].
In the interpolating case, we use properties of multivariate Lagrange polynomial interpolation to prove the existence of
interpolating schemes with maximal sum rule orders. These can be found by solving a linear system which can be reduced in
size by using symmetries. From this, we construct some new examples of smooth (C
2
,C
3
) interpolating
-subdivision schemes with maximal sum rule order and symmetric masks. The construction of associated dual schemes is also
discussed. 相似文献
5.
Horst Alzer 《Monatshefte für Mathematik》2000,131(3):179-188
A classical inequality for Euler’s gamma function states that
for all and with . We prove the following extension of this result. Let be the weighted power mean of of order r. The inequality
holds for all and with if and only if
(Received 3 April 2000; in revised form 26 June 2000) 相似文献
6.
Abstract. Given a finite set A and a distinguished function
, we study the set of all functions
that are continuous for all topologies for which f is continuous. The main result is a characterization of the functions f such that this set is trivial, that is, contains only the constant functions and the iterates of f . 相似文献
7.
Abstract. Weakly left ample semigroups are a class of semigroups that are (2,1) -subalgebras of semigroups of partial transformations, where the unary operation takes a transformation α to the identity map in the domain of α . It is known that there is a class of proper weakly left ample semigroups whose structure is determined by unipotent monoids acting on semilattices or categories. In
this paper we show that for every finite weakly left ample semigroup S , there is a finite proper weakly left ample semigroup
and an onto morphism from
to S which separates idempotents. In fact,
is actually a (2,1) -subalgebra of a symmetric inverse semigroup, that is, it is a left ample semigroup (formerly, left type A). 相似文献
8.
9.
10.
It is well known that the recurrence relations
are periodic, in the sense that they define periodic sequences for all choices of the initial data, and lead to sequences
with periods 2, 5 and 8, respectively. In this paper we determine all periodic recursions of the form
where are complex numbers, are non-zero and . We find that, apart from the three recursions listed above, only
lead to periodic sequences (with periods 6 and 8). The non-periodicity of (R) when (or and ) depends on the connection between (R) and the recurrence relations
and
We investigate these recursions together with the related
Each of (A), (B), and (C) leads to periodic sequences if k = 1 (with periods 6, 5, and 9, respectively). Also, for k = 2, (B) leads to periodicity with period 8. However, no other cases give rise to periodicity. We also prove that every real
sequence satisfying any of (A), (B), and (C) must be bounded. As a consequence, we find that for an arbitrary k, every rational sequence satisfying any of (A), (B), and (C) must be periodic.
(Received 27 June 2000; in revised form 5 January 2001) 相似文献
11.
12.
Clemens Heuberger 《Monatshefte für Mathematik》2001,132(4):325-339
In a recent paper [7] the author considered the family of parametrized Thue equations
for monic polynomials which satisfy
Under some technical conditions it could be proved that there is a computable constant such that for all integers the only integer solutions of the Diophantine equation satisfy .
In this paper, we give an explicit expression for depending on the polynomials .
(Received 5 September 2000; in revised form 30 December 2000) 相似文献
13.
A Fully Dynamic Algorithm for Planar Width 总被引：1，自引：0，他引：1
Chan 《Discrete and Computational Geometry》2003,30(1):17-24
Abstract. We show how to maintain the width of a set of n planar points subject to insertions and deletions of points in
amortized time per update. Previously, no fully dynamic algorithm with a guaranteed sublinear time bound was known. 相似文献
14.
Antonio Cañada Juan A. Montero Salvador Villegas 《Mediterranean Journal of Mathematics》2006,3(2):177-187
Let us consider the linear boundary value problem
where
and
is defined by
Classical Lyapunov inequality states that
for any function
where
The constant 4/L is optimal. Let us note that Lyapunov inequality is given in terms of
the usual norm in the space L1(0, L). In this paper we review some recent results on Lp Lyapunovtype inequalities,
, for ordinary and partial differential equations on a bounded and regular domain in
In the last case, it is showed that the relation between the quantities p and N/2 plays a crucial role, pointing out a deep difference with respect to the ordinary case. In the proof, the best constants
are obtained by using a related variational problem and Lagrange multiplier theorem. Finally, the linear results are combined
with Schauder fixed point theorem in the study of resonant nonlinear problems.
The authors have been supported by the Ministry of Science and Technology of Spain MTM2005- 01331 and by Junta de Andalucia
(FQM116). 相似文献
| ((0.1)) |
15.
Let and be the von Mangoldt function and M?bius function, respectively, x real and y“small” compared with x. This paper gives, for the first time, a non-trivial estimate of the sum
for all whenever . Correspondingly, it is also proved that
相似文献
16.
Yuri Bilu 《Combinatorica》1998,18(4):449-459
A of integers is sum-free if . Cameron conjectured that the number of sum-free sets is . As a step towards this conjecture, we prove that the number of sets satisfying
is .
Received: 22 July, 1996 相似文献
17.
We establish a new bound for the exponential sum
where λ is an element of the residue ring modulo a large prime number
and
are arbitrary subsets of the residue ring modulo p − 1 and γ (n) are any complex numbers with | γ (n)| ≦ 1.
Received: 15 June 2005 相似文献
18.
19.
20.
Abstract. Let I be a finite interval, r∈ N and ρ(t)= dist {t, I} , t∈ I . Denote by Δ
s
+
L
q
the subset of all functions y∈ L
q
such that the s -difference Δ
s
τ
y(t) is nonnegative on I ,
τ>0 . Further, denote by
, 0≤α<∞ , the classes of functions x on I with the seminorm ||x
(r)
ρ
α
||_ L
p
≤ 1 , such that Δ
s
τ
x≥ 0 , τ>0 . For s=0,1,2 , we obtain two-sided estimates of the shape-preserving widths
where M
n
is the set of all linear manifolds M
n
in L
q
, such that dim M
n
≤ n , and satisfying
. 相似文献