共查询到20条相似文献,搜索用时 15 毫秒
1.
In this article, we develop a computational method for an algorithmic process first posed by Polyrakis in 1996 in order to check whether a finite collection of linearly independent positive functions in C[a,b] forms a lattice-subspace. Lattice-subspaces are closely related to a cost minimization problem in the theory of finance that ensures the minimum-cost insured portfolio and this connection is further investigated here. Finally, we propose a computational method in order to solve the minimization problem and to calculate the minimum-cost insured portfolio. All of the numerical work is performed using the Matlab high-level language. 相似文献
2.
Based on fixed point theorems for monotone and mixed monotone operators in a normal cone, we prove that the nonlinear matrix equation always has a unique positive definite solution. A conjecture which is proposed in [X.G. Liu, H. Gao, On the positive definite solutions of the matrix equation Xs± ATX-tA= In, Linear Algebra Appl. 368 (2003) 83–97] is solved. Multi-step stationary iterative method is proposed to compute the unique positive definite solution. Numerical examples show that this iterative method is feasible and effective. 相似文献
3.
In [G. Marino, O. Polverino, R. Trombetti, On -linear sets of PG(3, q3) and semifields, J. Combin. Theory Ser. A 114 (5) (2007) 769–788] it has been proven that there exist six non-isotopic families ( i=0,…,5) of semifields of order q6 with left nucleus and center , according to the different geometric configurations of the associated -linear sets. In this paper we first prove that any semifield of order q6 with left nucleus , right and middle nuclei and center is isotopic to a cyclic semifield. Then, we focus on the family by proving that it can be partitioned into three further non-isotopic families: , , and we show that any semifield of order q6 with left nucleus , right and middle nuclei and center belongs to the family . 相似文献
4.
This paper is concerned with compactness for some topologies on the collection of bounded linear operators on Banach spaces. New versions of the Eberlein–Šmulian theorem and Day's lemma in the collection are established. Also we obtain a partial solution of the dual problem for the quasi approximation property, that is, it is shown that for a Banach space X if X** is separable and X* has the quasi approximation property, then X has the quasi approximation property. 相似文献
5.
Let T be an ergodic automorphism of a probability space, f a bounded measurable function, . It is shown that the property that the probabilities μ(| Sn( f)|> n) are of order n−p roughly corresponds to the existence of an approximation in L∞ of f by functions (coboundaries) g− g○ T, gLp. Similarly, the probabilities μ(| Sn( f)|> n) are exponentially small iff f can be approximated by coboundaries g− g○ T where g have finite exponential moments. RésuméSoit T un automorphisme ergodique d'un espace probabilisé, f une fonction bornée mesurable et . Une correspondance est établie entre l'existence de l'estimation des probabilités μ(| Sn( f)|> n) d'ordre n−p et l'existence de l'approximation dans L∞ de la fonction f par des cobords g− g○ T où g est “presque” dans Lp. De manière similaire, les probabilités μ(| Sn( f)|> n) sont d'ordre e −cn, pour un certain c>0, n=1,2… , si et seulement si f admet une approximation dans L∞ par des cobords g− g○ T avec g ayant des moments exponentiels. 相似文献
7.
The extension field where q is a prime divisor of ( P−1), has a unique structure. This paper describes this unique structure and uses it to derive formulas relating the trace values for elements in . These formulas can be refined for certain elements to produce a formula for the trace. 相似文献
8.
Let C be a smooth, geometrically connected, projective curve of genus g2 defined over . Here we follow a recent paper of Savin and study the parameters (size, dimension, minimal distance) of algebraic codes constructed using vector bundles E on C. We need to construct vector bundles defined over and with certain numerical invariants (degree, rank h0( C, E), order of 1-stability). 相似文献
9.
For all integers m3 and all natural numbers a1, a2,…, am−1, let n= R( a1, a2,…, am−1) represent the least integer such that for every 2-coloring of the set {1,2,…, n} there exists a monochromatic solution to | Let t=min{a1,a2,…,am−1} and b=a1+a2++am−1−t. In this paper it is shown that whenever t=2, R(a1,a2,…,am−1)=2b2+9b+8.
It is also shown that for all values of t, R(a1,a2,…,am−1)tb2+(2t2+1)b+t3.
相似文献
10.
Let
k be an algebraically closed field of characteristic 2. We prove that the restricted nilpotent commuting variety
, that is the set of pairs of (
n×
n)-matrices (
A,
B) such that
A2=
B2=[
A,
B]=0, is equidimensional.
can be identified with the ‘variety of
n-dimensional modules’ for
, or equivalently, for
k[
X,
Y]/(
X2,
Y2). On the other hand, we provide an example showing that the restricted nilpotent commuting variety is not equidimensional for fields of characteristic >2. We also prove that if
e2=0 then the set of elements of the centralizer of
e whose square is zero is equidimensional. Finally, we express each irreducible component of
as a direct sum of indecomposable components of varieties of
-modules.
相似文献
11.
The solution of the linear operator equation:
An-1X+
An-2XB++
AXBn-2+
XBn-1=
Y is given by
if the spectra of
A and
B are in the sector {
z:
z≠0,-
π/
n<arg
z<
π/
n}.
相似文献
12.
We develop in this paper methods for studying the implicitization problem for a rational map
defining a hypersurface in
, based on computing the determinant of a graded strand of a Koszul complex. We show that the classical study of Macaulay resultants and Koszul complexes coincides, in this case, with the approach of approximation complexes and we study and give a geometric interpretation for the acyclicity conditions.Under suitable hypotheses, these techniques enable us to obtain the implicit equation, up to a power, and up to some extra factor. We give algebraic and geometric conditions for determining when the computed equation defines the scheme theoretic image of
, and, what are the extra varieties that appear. We also give some applications to the problem of computing sparse discriminants.
相似文献
13.
With the help of the concept of Kronecker map, an explicit solution for the matrix equation
X−
AXF=
C is established. This solution is neatly expressed by a symmetric operator matrix, a controllability matrix and an observability matrix. In addition, the matrix equation
is also studied. An explicit solution for this matrix equation is also proposed by means of the real representation of a complex matrix. This solution is neatly expressed by a symmetric operator matrix, two controllability matrices and two observability matrices.
相似文献
14.
We prove the global well-posedness and scattering for the defocusing
-subcritical (that is, 2<
γ<3) Hartree equation with low regularity data in
,
d3. Precisely, we show that a unique and global solution exists for initial data in the Sobolev space
with
s>4(
γ−2)/(3
γ−4), which also scatters in both time directions. This improves the result in [M. Chae, S. Hong, J. Kim, C.W. Yang, Scattering theory below energy for a class of Hartree type equations, Comm. Partial Differential Equations 33 (2008) 321–348], where the global well-posedness was established for any
s>max(1/2,4(
γ−2)/(3
γ−4)). The new ingredients in our proof are that we make use of an interaction Morawetz estimate for the smoothed out solution
Iu, instead of an interaction Morawetz estimate for the solution
u, and that we make careful analysis of the monotonicity property of the multiplier
m(
ξ)
ξp. As a byproduct of our proof, we obtain that the
Hs norm of the solution obeys the uniform-in-time bounds.
相似文献
15.
In this paper we will treat a generalization of inner and outer approximations of fuzzy sets, which we will call
-inner and
-outer approximations respectively (
being any finite set of rational numbers in [0,1]). In particular we will discuss the case of those fuzzy sets which are definable in the logic
by means of step functions from the hypercube [0,1]
k and taking value in an arbitrary (finite) subset of
. Then, we will show that if a fuzzy set is definable as truth table of a formula of
, then both its
-inner and
-outer approximation are definable as truth table of formulas of
. Finally, we will introduce a generalization of abstract approximation spaces and compare our approach with the notion of fuzzy rough set.
相似文献
16.
In this paper a class of polynomial interior-point algorithms for horizontal linear complementarity problem based on a new parametric kernel function, with parameters
p[0,1] and
σ≥1, are presented. The proposed parametric kernel function is not exponentially convex and also not strongly convex like the usual kernel functions, and has a finite value at the boundary of the feasible region. It is used both for determining the search directions and for measuring the distance between the given iterate and the
μ-center for the algorithm. The currently best known iteration bounds for the algorithm with large- and small-update methods are derived, namely, and , respectively, which reduce the gap between the practical behavior of the algorithms and their theoretical performance results. Numerical tests demonstrate the behavior of the algorithms for different results of the parameters
p,
σ and
θ.
相似文献
17.
Our aim in this paper is to investigate the global asymptotic stability of all positive solutions of the higher order nonlinear difference equation
where
B,
C and
α,
β,
γ are positive,
k {1, 2, 3, … }, and the initial conditions
x−2k+1, … ,
x−1,
x0 are positive real numbers. We show that the unique positive equilibrium of the equation is globally asymptotically stable and has some basins that depend on certain conditions posed on the coefficients. Our concentration is on invariant intervals, the character of semicycles, and the boundedness of the above mentioned equation. Our final comments are about informative examples.
相似文献
18.
In this paper, we prove that a set
of
q5+
q4+
q3+
q2+
q+1 lines of
with the properties that (1) every point of
is incident with either 0 or
q+1 elements of
, (2) every plane of
is incident with either 0, 1 or
q+1 elements of
, (3) every solid of
is incident with either 0, 1,
q+1 or 2
q+1 elements of
, and (4) every hyperplane of
is incident with at most
q3+3
q2+3
q members of
, is necessarily the set of lines of a regularly embedded split Cayley generalized hexagon
in
.
相似文献
19.
Among binary images of a Type II code over
with respect to the trace-orthogonal bases, it has been unknown whether the minimum Hamming weights depend on the choice of bases or not; the minimum Hamming weights of the binary images of known Type II codes have been independent of the choice of bases.In this paper we give a complete list of Type II codes over
of length 8 up to a certain equivalence. This list shows us an example of a Type II code of which minimum Lee weight depends on the choice of a basis.
相似文献
20.
We give a sufficient condition for strictly positive definiteness in . The result is based on the question how sparse subsets of can be to guarantee linear independence of the exponentials.
相似文献