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1.
Weighted Composition Operators on Bergman and Dirichlet Spaces 总被引:3,自引:0,他引:3
Let H() denote a functional Hilbert space of analytic functions on a domain . Let w : C and : be such that w f is in H() for every f in H(). The operator wC
given by f w f is called a weighted composition operator on H(). In this paper we characterize such operators and those for which (wC
)* is a composition operator. Compact weighted composition operators on some functional Hilbert spaces are also characterized. We give sufficient conditions for the compactness of such operators on weighted Dirichlet spaces. 相似文献
2.
Timothy S. Norfolk 《Numerical Algorithms》2000,25(1-4):279-291
In this paper, we explore the asymptotic distribution of the zeros of the partial sums of the family of entire functions of order 1 and type 1, defined by G(,,z)=0
1(t)t
–1×(1–t)–1e
zt
dt, where Re,Re>0, is Riemann-integrable on [0,1], continuous at t=0, 1 and satisfies (0)(1)0. 相似文献
3.
E. Csáki 《Probability Theory and Related Fields》1980,54(3):287-301
Summary Let W(t) be a standard Wiener process and let f(x) be a function from the compact class in Strassen's law of the iterated logarithm. We investigate the lim inf behavior of the variable sup ¦W(xT)(2T loglog T)–1/2–f(x)¦, 0x1 suitably normalized as T.This extends Chung's result valid for f(x)0, stating that lim inf.[ sup ¦(2T loglogT)–1/2
W(xT)¦(loglog T)–1]=/4 a.s. T 0x1 相似文献
4.
Roeland P. van der Marel 《BIT Numerical Mathematics》1990,30(3):516-528
This paper deals with polynomial approximations(x) to the exponential function exp(x) related to numerical procedures for solving initial value problems. Motivated by stability requirements, we present a numerical study of the largest diskD()={z C: |z+|} that is contained in the stability regionS()={z C: |(z)|1}. The radius of this largest disk is denoted byr(), the stability radius. On the basis of our numerical study, several conjectures are made concerningr
m,p=sup {r():
m,p}. Here
m, p (1pm; p, m integers) is the class of all polynomials(x) with real coefficients and degree m for which(x)=exp(x)+O(x
p+1) (forx 0). 相似文献
5.
Jean -Michel Bismut 《Probability Theory and Related Fields》1981,55(3):331-350
Summary A stochastic differential equation with smooth coefficients is considered, which defines a continuous flow
t
, (, .) of C
+8
mappings of R
d
in R
d
. If z
t
is a continuous semi-martingale,
t
,(,zt)s> is proved to be a semi-martingale, for which an Ito type formula is established. It is shown that a.s., for any t,
t
(, .) is an onto diffeomorphism. If z
t
is a continuous semi-martingale,
t
–1
,(,z
t
) is proved to be a semi-martingale, whose Ito decomposition is explicitly found.The support of the University of British Columbia is gratefully acknowledged. 相似文献
6.
Sanming Zhou 《Czechoslovak Mathematical Journal》1998,48(1):45-53
Let G be a graph with order p, size q and component number . For each i between p – and q, let
be the family of spanning i-edge subgraphs of G with exactly components. For an integer-valued graphical invariant if H H
is an adjacent edge transformation (AET) implies |(H)-(H')|1 then is said to be continuous with respect to AET. Similarly define the continuity of with respect to simple edge transformation (SET). Let M
j() and m
j() be the invariants defined by
. It is proved that both M
p–() and m
p–(;) interpolate over
, if is continuous with respect to AET, and that M
j() and m
j() interpolate over
, if is continuous with respect to SET. In this way a lot of known interpolation results, including a theorem due to Schuster etc., are generalized. 相似文献
7.
Let (Z
n
)
n 0 be a supercritical Galton–Watson process with finite re-production mean and normalized limit W=lim
n –n
Z
n
. Let further : [0,) [0,) be a convex differentiable function with (0)=(0)=0 and such that (
) is convex with concave derivative for some n 0. By using convex function inequalities due to Topchii and Vatutin, and Burkholder, Davis and Gundy, we prove that 0 < E
(W) < if, and only if,
, where
We further show that functions (x)=x
L(x) which are regularly varying of order 1 at are covered by this result if {2
n
: n 0 } and under an additional condition also if =2
n
for some n0. This was obtained in a slightly weaker form and analytically by Bingham and Doney. If > 1, then
grows at the same order of magnitude as (x) so that
and E
(Z
1)< are equivalent. However, =1 implies
and hence that
is a strictly stronger condition than E
(Z
1) < . If (x)=x log
p
x for some p > 0 it can be shown that
grows like x log
p+1
x, as x. For this special case the result is due to Athreya. As a by-product we also provide a new proof of the Kesten–Stigum result that E
Z
1 log Z
1 < and EW > 0 are equivalent. 相似文献
8.
Ioannis Karatzas 《Applied Mathematics and Optimization》1981,7(1):175-189
We consider the problem of optimally tracking the random demandx+w
t, w. Brownian motion, by a nondecreasing process. adapted to the Brownian past, so as to minimize the expected lossE
0
T
(x+wt–t)dt. The decision problem is reduced to a free boundary one, and the latter is studied and solved for a large class of cost functions().This research was supported in part by the Air Force Office of Scientific Research, under AF-AFOSR 77-3063. 相似文献
9.
With appropriate regularity assumptions on the increasing concave function x=(t)<0, the hitting time density p(t) for a transient curve x=(t) by a 1-dimensional Brownian motion is shown to satisfy
Here r is the probability of eventually hitting the curve and (t)=t
–1/2(t). 相似文献
10.
E. P. Dolzhenko 《Mathematical Notes》1996,60(2):130-136
Letd(;z, t) be the smallest diameter of the arcs of a Jordan curve with endsz andt. Consider the rapidity of decreasing ofd(;)=sup{d(;z, t):z, t , ¦z–t¦} (as 0,0) as a measure of nicety of . Letg(x) (x0) be a continuous and nondecreasing function such thatg(x)x,g(0)=0. Put¯g(x)=g(x)+x, h(x)=(¯g(x))2. LetH(x) be an arbitrary primitive of 1/h
–1(x). Note that the functionH
–1
x is positive and increasing on (–, +),H
–1 0 asx– andH
–1+ asx +. The following statement is proved in the paper.Translated fromMatematicheskie Zametki, Vol. 60, No. 2, pp. 176–184, August, 1996.This research was supported by the Russian Foundation for Basic Research under grant No. 93-01-00236 and by the International Science Foundation under grant No. NCF000. 相似文献
11.
Jean Legras 《Numerische Mathematik》1966,8(1):14-28
Sommaire La solution stricte d'un système différentiel linéaire à coefficients constants [d /d t] = [A] [] + [f (t) ] est donnée par: [ (t)]= [eAt] [ (0) ] + f [eA(t–)] [f (T) ] d .Cette relation, utilisée dans une méthode de pas à pas, permet le calcul de [(t+u)] en fonction de [(t)]. La mise en oeuvre numérique de cette formule nécessite le calcul de [eA] et de l'intégrale de matrice du second membre.Le sujet de cette étude est la mise au point de techniques d'approximation permettant le calcul effectif de [e
Aµ] et de l'intégrale de matrice par des méthodes qui peuvent s'adapter en particulier aux systèmes différentiels à très grand nombre d'inconnues, qui apparaissent par exemple dans l'approximation par discrétisation enx ety, de l'équation aux dérivées partielles, dite de la chaleur. 相似文献
12.
S. V. Petras 《Journal of Mathematical Sciences》1984,24(3):380-386
The behavior of the poles zn(), n=1,2,... of the scattering matrix of the operatorl
u=–u(x), x , (u/n)+(x)u|=0 as 0 is considered. It is proved that |zn()–zn|=0((1/2)qn), where qn is the order of the pole of the scattering matrix for the operator 0u=–u, u/=0.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 117, pp. 183–191, 1981. 相似文献
13.
Let and be two hyperbolic simply connected domains in the extended complex plane C¯ = C¯ {}. We derive sharp upper bounds for the modulus of the nth derivative of a holomorphic, resp. meromorphic function f: at a point z
0 . The bounds depend on the densities (z
0) and (f(z
0)) of the Poincaré metrics and on the hyperbolic distances of the points z
0 and f(z
0) to the point . 相似文献
14.
We construct an asymptotic formula for a sum function for
a
(), where
a
() is the sum of the ath powers of the norms of divisors of the Gaussian integer on an arithmetic progression 0 (mod ) and in a narrow sector 1 arg < 2. For this purpose, we use a representation of
a
(n) in the form of a series in the Ramanujan sums. 相似文献
15.
Philippe Bonnet 《Transformation Groups》2002,7(1):3-14
In this paper we establish two results concerning algebraic (,+)-actions on
n
. First, let be an algebraic (,+)-action on 3. By a result of Miyanishi, its ring of invariants is isomorphic to [t
1,t
2]. Iff
1,f
2 generate this ring, the quotient map of is the mapF:32,x(f
1(x), f2(x)). By using some topological arguments we prove thatF is always surjective. Secon, we are interested in dominant polynomial mapsF:
n
n-1
whose connected components of their generic fibers are contractible. For such maps, we prove the existence of an algebraic (,+)-action on
n
for whichF is invariant. Moreover we give some conditions so thatF*([t
1,...,t
n-1
]) is the ring of invariants of .Dedicated to all my friends and my family 相似文献
16.
Yimin Xiao 《Journal of Theoretical Probability》1997,10(4):849-866
Let X(t) (tR) be a real-valued centered Gaussian process with stationary increments. We assume that there exist positive constants
0, C
1, and c
2 such that for any tR and hR with |h|0
and for any 0r<min{|t|, 0}
where
is regularly varying at zero of order (0 < < 1). Let be an inverse function of near zero such that (s)=(s) log log(1/s) is increasing near zero. We obtain exact estimates for the weak -variation of X(t) on [0,a]. 相似文献
17.
V. A. Slousch 《Journal of Mathematical Sciences》2003,115(2):2272-2278
Let A be a self-adjoint elliptic second-order differential operator, let (, ) be an inner gap in the spectrum of A, and let B(t) = A + tW
*
W, where W is a differential operator of higher order. Conditions are obtained under which the spectrum of the operator B(t) in the gap (, ) is either discrete, or does not accumulate to the right-hand boundary of the spectral gap, or is finite. The quantity N(, A, W, ), (, ), > 0 (the number of eigenvalues of the operator B(t) passing the point (, ) as t increases from 0 to ) is considered. Estimates of N(, A, W, ) are obtained. For the perturbation W
*
W of a special form, the asymptotics of N(, A, W, ) as + is given. Bibliography: 5 titles. 相似文献
18.
Let X={X(t):tR} be a Lévy process and a non-decreasing, right continuous, bounded function with (–)=0 (((1+u
2)/u
2)d(u) is the Lévy measure). In this paper we define the Donsker delta function (X(t)–a), t>0 and aR, as a generalized Lévy functional under the condition that (0)–(0–)>0. This leads us to define F(X(t)) for any tempered distribution F, and as an application, we derive an Itô formula for F(X(t)) when has jumps at 0 and 1. 相似文献
19.
20.
Let w() be a positive weight function on the unit circle of the complex plane. For a sequence of points {
k
}
k = 1
included in a compact subset of the unit disk, we consider the orthogonal rational functions
n
that are obtained by orthogonalization of the sequence { 1, z / 1, z
2 / 2, ... } where
, with respect to the inner product
In this paper we discuss the behaviour of
n
(t) for t = 1 and n under certain conditions. The main condition on the weight is that it satisfies a Lipschitz–Dini condition and that it is bounded away from zero. This generalizes a theorem given by Szeg in the polynomial case, that is when all
k
= 0. 相似文献