The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
We study the transient flow of an isothermal and incompressible Bingham fluID. Similar models arise in completely different contexts as, for instance, in material science, image processing and differential geometry. For the two-dimensional flow in a bounded domain we show the extinction in a finite time even under suitable nonzero external forces. We also consIDer the special case of a threedimensional...
A compact Riemann surfaceX of genusg > 1 is said to be ap-hyperelliptic ifX admits a conformal involution ρ for whichX/ρ has genusp. This notion is the particular case of so called cyclic (q, n)-gonal surface which is defined as the one admitting a conformal automorphism δ of ordern such that X/δ has genusq. It is known that forg > 4p + 1, ρ is unique And so central in the automorphism group...
We characterize quasi-reflexive barrelled and complete locally convex Hausdorff spaces with a basis in terms of the properties of this basis. Moreover we prove that a complete, barrelled lcHs with a basis is quasi-reflexive of order one if and only if for every power bounded operatorT, eitherT orT′ is mean ergodic.
We prove that Eberlein's theorem holds for the Mackey* topology in the dualX* of a Banach space. This improves a result of Howard. We prove, too, that in general the spaceX* endowed with the Mackey* topology is not angelic.
Let X be a real Banach space, let A: D(A) ⊆ X ⇝ X be an m-dissipative operator, let I a nonempty, bounded interval And let K: $$ K:I \rightsquigarrow \overline {D(A)} $$ be a given multi-valued function. By using the concept of A-quasi-tangent set introduced by Cârjă, Necula, Vrabie [8] And [9] And using a tangency condition expressed in the terms of this concept, we establish a necessary And...
Casella et al. [2, (2009)] proved that, under very general conditions, for normal linear models the Bayes factor for a wide class of prior distributions, including the intrinsic priors, is consistent when the number of parameters does not grow with the sample sizen. The special attention paid to the intrinsic priors is due to the fact that they are nonsubjective priors, and thus accessible priors...
Following Sinha and Karn [9], a relatively compact subset K of a Banach space E is said to be p-compact if for some sequence (xn) ∈ lp(E), K ⊂ {Σnaxxn | (an) ∈ Bℓ′p}. In [4], Delgado, Oja, Piñeiro, and Serrano investigated the p-approximation property, in which one only requires finite rank approximation of the identity on p-compact subsets. We investigate analogous concepts...
We discuss some open problems in the Geometry of Banach spaces having Ramsey-theoretic flavor. The problems are exposed together with well known results related to them.
We collect facts about Gul’ko, descriptive, Gruenhage, and fragmentable compact spaces. In several instances we provide direct proofs of the results discussed. We show how they reflect the geometrical structure of corresponding Banach spaces C(K). In particular, we provide proofs, by a simple transfer of Day’s norm, of recent renorming results for the duals C(K)* due to M. Raja and to R. Smith.
It is an open problem if any separable compact space K whose function space C(K) with the cylindrical σ-algebra is a standard measurable space, embeds in the space of the first Baire class functions on the Cantor set, with the pointwise topology. We prove that this is true for separable linearly ordered compacta. Other problems discussed in this note concern the Borel structures in C(K) generated...
We state and comment a number of open problems on the descriptive complexity of some natural classes of Banach spaces. We characterize the separable dual spaces on which the set of equivalent dual norms is analytic.
We list a number of problems in several topics related to compactness in nonseparable Banach spaces. Namely, about the Hilbertian ball in its weak topology, spaces of continuous functions on Eberlein compacta, WCG Banach spaces, Valdivia compacta and Radon-Nikodým compacta.
This survey’s first object is to introduce the reader to Lindelöf Σ-spaces; since the author would like this introduction to be useful for postgraduate students and non-specialists in the area, most of the basic results are given with complete proofs. The second object is to make an overview of the recent progress achieved in the study of Lindelöf Σ-spaces. Several popular topics are presented together...
The following open problem is stated: Is there a non-normable Fréchet space E such that every continuous linear operator T on E has the form T = λI + S, where S maps a 0-neighbourhood of E into a bounded set? A few remarks and the relation of this question with other still open problems on operators between Fréchet spaces are mentioned.
Several attempts to transfer methods of the classical descriptive set theory to study measurability in nonseparable metrizable or more general topological spaces are presented. In particular, the theories of K-analytic spaces and of absolute Souslin metrizable spaces give quite interesting results. The spaces which are results of the Souslin operation applied to the families of Borel sets (Čech-analytic...
We say that a Banach space C(K) of all real-valued continuous functions on a compact Hausdorff space K with the supremum norm has few operators if for every linear bounded operator T on C(K) we have T=gI+S or T*=g*I+S where g is continuous on K, g* is Borel on K and S are weakly compact on C(K) or C*(K) respectively. C(K) spaces with few operators share some properties with the spaces of Gowers and...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.