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1.
We study holomorphic solutions f of the generalized Dhombres equation f(zf(z))=φ(f(z)), z∈C, where φ is in the class E of entire functions. We show, that there is a nowhere dense set E0⊂E such that for every φ∈E?E0, any solution f vanishes at 0 and hence, satisfies the conditions for local analytic solutions with fixed point 0 from our recent paper. Consequently, we are able to provide a characterization of solutions in the typical case where φ∈E?E0. We also show that for polynomial φ any holomorphic solution on C?{0} can be extended to the whole of C. Using this, in special cases like φ(z)=zk+1, k∈N, we can provide a characterization of the analytic solutions in C. 相似文献
2.
Stevo Stevi? 《Applied mathematics and computation》2010,215(11):3950-1448
The boundedness of the composition operator Cφf(z)=f(φ(z)) from the Hardy space , where X is the upper half-plane or the unit disk D={z∈C:|z|<1} in the complex plane C, to the nth weighted-type space, where φ is an analytic self-map of X, is characterized. 相似文献
3.
José Ángel Peláez 《Journal of Functional Analysis》2008,255(6):1403-1418
If X⊂Y are two classes of analytic functions in the unit disk D and θ is an inner function, θ is said to be (X,Y)-improving, if every function f∈X satisfying fθ∈Y must actually satisfy fθ∈X. This notion has been recently introduced by K.M. Dyakonov. In this paper we study the (X,Y)-improving inner functions for several pairs of spaces (X,Y). In particular, we prove that for any p∈(0,1) the (Qp,BMOA)-improving inner functions and the (Qp,B)-improving inner functions are precisely the inner functions which belong to the space Qp. Here, B is the Bloch space. We also improve some results of Dyakonov on the subject regarding Lipschitz spaces and Besov spaces. 相似文献
4.
In this paper, the approximation properties of q-Durrmeyer operators Dn,q(f;x) for f∈C[0,1] are discussed. The exact class of continuous functions satisfying approximation process limn→∞Dn,q(f;x)=f(x) is determined. The results of the paper provide an elaboration of the previously-known ones on operators Dn,q. 相似文献
5.
A weighted composition operator Cψ,φ takes an analytic map f on the open unit disc of the complex plane to the analytic map ψ⋅f°φ where φ is an analytic map of the open unit disc into itself and ψ is an analytic map on the open unit disc. This paper studies the invertibility of such operators. The two maps ψ and φ are characterized when Cψ,φ acts on the Hardy-Hilbert space of the unit disc H2(D). Depending upon the nature of the fixed points of φ spectra are then investigated. 相似文献
6.
William M. Higdon 《Journal of Functional Analysis》2005,220(1):55-75
Let φ:D→D be a non-constant linear fractional transformation (necessarily of the form ). Let D denote the Dirichlet space of analytic functions. We determine the spectrum of the composition operator C?:D→D defined by C?(f)=f°φ. Eigenfunctions for the operator C?:H2→H2 frequently do not belong to the space D. However, spectral results for the operator C?:D→D, much like those that have already been demonstrated for the operator C?:H2→H2, are presented in this paper. 相似文献
7.
Pierrette Cassou-Noguès 《Journal of Pure and Applied Algebra》2009,213(5):711-723
Let φ=(f,g) be an endomorphism of the affine plane C2 defined by two polynomials f,g∈C[x,y] and let Λ={Cb∣b∈C} be the pencil of lines Cb defined by x=b. We shall consider the smoothness criterion of the image curve φ(Cb). The hypersurface V whose coordinate ring is C[x,f,g] and the normalization of V will play interesting roles in analyzing the properties of the set φ(Λ)={φ(Cb)∣b∈C}. 相似文献
8.
Emma D'Aniello 《Journal of Mathematical Analysis and Applications》2006,321(2):867-879
Let C be the collection of continuous self-maps of the unit interval I=[0,1] to itself. For f∈C and x∈I, let ω(x,f) be the ω-limit set of f generated by x, and following Block and Coppel, we take Q(x,f) to be the intersection of all the asymptotically stable sets of f containing ω(x,f). We show that Q(x,f) tells us quite a bit about the stability of ω(x,f) subject to perturbations of either x or f, or both. For example, a chain recurrent point y is contained in Q(x,f) if and only if there are arbitrarily small perturbations of f to a new function g that give us y as a point of ω(x,g). We also study the structure of the map Q taking (x,f)∈I×C to Q(x,f). We prove that Q is upper semicontinuous and a Baire 1 function, hence continuous on a residual subset of I×C. We also consider the map given by x?Q(x,f), and find that this map is continuous if and only if it is a constant map; that is, only when the set is a singleton. 相似文献
9.
Let Un ⊂ Cn[a, b] be an extended Chebyshev space of dimension n + 1. Suppose that f0 ∈ Un is strictly positive and f1 ∈ Un has the property that f1/f0 is strictly increasing. We search for conditions ensuring the existence of points t0, …, tn ∈ [a, b] and positive coefficients α0, …, αn such that for all f ∈ C[a, b], the operator Bn:C[a, b] → Un defined by satisfies Bnf0 = f0 and Bnf1 = f1. Here it is assumed that pn,k, k = 0, …, n, is a Bernstein basis, defined by the property that each pn,k has a zero of order k at a and a zero of order n − k at b. 相似文献
10.
Geir Agnarsson 《Discrete Mathematics》2006,306(17):2021-2030
A reflexive graph is a simple undirected graph where a loop has been added at each vertex. If G and H are reflexive graphs and U⊆V(H), then a vertex map f:U→V(G) is called nonexpansive if for every two vertices x,y∈U, the distance between f(x) and f(y) in G is at most that between x and y in H. A reflexive graph G is said to have the extension property (EP) if for every reflexive graph H, every U⊆V(H) and every nonexpansive vertex map f:U→V(G), there is a graph homomorphism φf:H→G that agrees with f on U. Characterizations of EP-graphs are well known in the mathematics and computer science literature. In this article we determine when exactly, for a given “sink”-vertex s∈V(G), we can obtain such an extension φf;s that maps each vertex of H closest to the vertex s among all such existing homomorphisms φf. A reflexive graph G satisfying this is then said to have the sink extension property (SEP). We then characterize the reflexive graphs with the unique sink extension property (USEP), where each such sink extensions φf;s is unique. 相似文献
11.
We completely characterize the boundedness and compactness of composition operators from the space of Cauchy transforms on the unit disk D, into the Bloch-type space Bν as well as the little Bloch-type space Bν,0, consisting respectively of all holomorphic functions f on D such that supz∈Dν(z)|f′(z)|<∞, that is, of all holomorphic functions f on D such that lim|z|→1ν(z)|f′(z)|=0, for some weight function ν. As a byproduct of our results, norm of the operator is calculated when Bν is replaced by Bν/C. 相似文献
12.
13.
Ciprian G. Gal 《Journal of Mathematical Analysis and Applications》2007,333(2):971-983
In this paper we consider the nonlinear differential equation with deviated argument u′(t)=Au(t)+f(t,u(t),u[φ(u(t),t)]), t∈R+, in a Banach space (X,‖⋅‖), where A is the infinitesimal generator of an analytic semigroup. Under suitable conditions on the functions f and φ, we prove a global existence and uniqueness result for the above equation. 相似文献
14.
We consider the problem of analytic continuation with inaccurate data from a finite subset U of a domain D of C
n to a point z
0D\U for the functions f belonging to a bounded correctness set V in a Hilbert space H(D) of analytic functions in D. In the case when H(D) is a Hilbert space with a reproducing kernel, we find constructive formulas for calculating the optimal error, the optimal function, and the optimal linear algorithm for extrapolation to a point z
0 for functions in V whose approximate values are given on a set U. Moreover, we study the asymptotics of the optimal error in the case when the errors of initial data vanish. 相似文献
15.
Let X be a topological space and let F be a filter on N, recall that a sequence (xn)n∈N in X is said to be F-convergent to the point x∈X, if for each neighborhood U of x, {n∈N:xn∈U}∈F. By using F-convergence in ?1 and in Banach spaces, we characterize the P-filters, the P-filters+, the weak P-filters, the Q-filters, the Q-filters+, the weak Q-filters, the selective filters and the selective+ filters. 相似文献
16.
S. Albeverio S. Kuzhel S. Torba 《Journal of Mathematical Analysis and Applications》2008,338(2):1267-1281
A p-adic Schrödinger-type operator Dα+VY is studied. Dα (α>0) is the operator of fractional differentiation and (bij∈C) is a singular potential containing the Dirac delta functions δx concentrated on a set of points Y={x1,…,xn} of the field of p-adic numbers Qp. It is shown that such a problem is well posed for α>1/2 and the singular perturbation VY is form-bounded for α>1. In the latter case, the spectral analysis of η-self-adjoint operator realizations of Dα+VY in L2(Qp) is carried out. 相似文献
17.
E.F. Clifford 《Journal of Mathematical Analysis and Applications》2005,312(1):195-204
We prove a value distribution result which has several interesting corollaries. Let k∈N, let α∈C and let f be a transcendental entire function with order less than 1/2. Then for every nonconstant entire function g, we have that (f○g)(k)−α has infinitely many zeros. This result also holds when k=1, for every transcendental entire function g. We also prove the following result for normal families. Let k∈N, let f be a transcendental entire function with ρ(f)<1/k, and let a0,…,ak−1,a be analytic functions in a domain Ω. Then the family of analytic functions g such that
18.
N.H. Guersenzvaig 《Linear algebra and its applications》2010,432(10):2691-2700
Let f,g∈Z[X] be monic polynomials of degree n and let C,D∈Mn(Z) be the corresponding companion matrices. We find necessary and sufficient conditions for the subalgebra Z〈C,D〉 to be a sublattice of finite index in the full integral lattice Mn(Z), in which case we compute the exact value of this index in terms of the resultant of f and g. If R is a commutative ring with identity we determine when R〈C,D〉=Mn(R), in which case a presentation for Mn(R) in terms of C and D is given. 相似文献
19.
Eva A. Gallardo-Gutiérrez Jonathan R. Partington 《Journal of Functional Analysis》2010,258(11):3593-3603
Boundedness (resp. compactness) of weighted composition operators Wh,φ acting on the classical Hardy space H2 as Wh,φf=h(f○φ) are characterized in terms of a Nevanlinna counting function associated to the symbols h and φ whenever h∈BMOA (resp. h∈VMOA). Analogous results are given for Hp spaces and the scale of weighted Bergman spaces. In the latter case, BMOA is replaced by the Bloch space (resp. VMOA by the little Bloch space). 相似文献
20.
Stephan Ruscheweyh Luis Salinas 《Journal of Mathematical Analysis and Applications》2004,291(2):596-604
An analytic function f(z) in the unit disc D is called stable if sn(f,·)/f?1/f holds for all for . Here sn stands for the nth partial sum of the Taylor expansion about the origin of f, and ? denotes the subordination of analytic functions in . We prove that (1−z)λ, λ∈[−1,1], are stable. The stability of turns out to be equivalent to a famous result of Vietoris on non-negative trigonometric sums. We discuss some generalizations of these results, and related conjectures, always with an eye on applications to positivity results for trigonometric and other polynomials. 相似文献