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Tytuł:
A note on the general moment problem
Autorzy:
El Azhar, Hamza
Hanine, Abdelouahab
Zerouali, El Hassan
Powiązania:
https://bibliotekanauki.pl/articles/29519750.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
general moment problem
charge sequences
atomic measure
Opis:
In this note we show that given an indeterminate Hamburger moment sequence, it is possible to perturb the first moment in such way that the obtained sequence remains an indeterminate Hamburger moment sequence. As a consequence we prove that every sequence of real numbers is a moment sequence for a signed discrete measure supported in $ \mathbb{R}_+ $.
Źródło:
Opuscula Mathematica; 2024, 44, 3; 359-372
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An inequality for imaginary parts of eigenvalues of non-compact operators with Hilbert-Schmidt Hermitian components
Autorzy:
Gil’, Michael
Powiązania:
https://bibliotekanauki.pl/articles/29519485.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
Hilbert space
linear operators
eigenvalues
Opis:
Let $ A $ be a bounded linear operator in a complex separable Hilbert space, $ A^∗ $ be its adjoint one and $ A_I := (A − A^∗)//(2i) $. Assuming that $A_I $ is a Hilbert-Schmidt operator, we investigate perturbations of the imaginary parts of the eigenvalues of $ A $. Our results are formulated in terms of the “extended” eigenvalue sets in the sense introduced by T. Kato. Besides, we refine the classical Weyl inequality $ \Sigma_{k=1}^\infty (Im \lambda_k (A))^2 ≤ N_2^2 (A_I) $, where $ λk(A) (k = 1, 2, . . .) $ are the eigenvalues of $ A $ and $ N_2(·) $ is the Hilbert-Schmidt norm. In addition, we discuss applications of our results to the Jacobi operators.
Źródło:
Opuscula Mathematica; 2024, 44, 2; 241-248
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anisotropic p-Laplace Equations on long cylindrical domain
Autorzy:
Jana, Purbita
Powiązania:
https://bibliotekanauki.pl/articles/29519481.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
pseudo p-Laplace equation
cylindrical domain
asymptotic analysis
Opis:
The main aim of this article is to study the Poisson type problem for anisotropic p-Laplace type equation on long cylindrical domains. The rate of convergence is shown to be exponential, thereby improving earlier known results for similar type of operators. The Poincaré inequality for a pseudo p-Laplace operator on an infinite strip-like domain is also studied and the best constant, like in many other situations in literature for other operators, is shown to be the same with the best Poincaré constant of an analogous problem set on a lower dimension.
Źródło:
Opuscula Mathematica; 2024, 44, 2; 249-265
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cesàro summability of Taylor series in higher order weighted Dirichlet-type spaces
Autorzy:
Ghara, Soumitra
Gupta, Rajeev
Reza, Md. Ramiz
Powiązania:
https://bibliotekanauki.pl/articles/29519753.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
weighted Dirichlet-type integrals
Cesàro means
summability
Hadamard multiplication
Opis:
For a positive integer $ m $ and a finite non-negative Borel measure $ \mu $ on the unit circle, we study the Hadamard multipliers of higher order weighted Dirichlet-type spaces $ \mathcal{H}_{\mu,m} $. We show that if $ \alpha > 1/2 $, then for any $ f $ in $ \mathcal{H}_{\mu,m} $, the sequence of generalized Cesàro sums $ { \sigma_n^\alpha | f | } $ converges to $ f $. We further show that if $ \alpha = 1/2 $ then for the Dirac delta measure supported at any point on the unit circle, the previous statement breaks down for every positive integer $ m $.
Źródło:
Opuscula Mathematica; 2024, 44, 3; 373-390
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conditional mean embedding and optimal feature selection via positive definite kernels
Autorzy:
Jorgensen, Palle E.T.
Song, Myung-Sin
Tiang, James
Powiązania:
https://bibliotekanauki.pl/articles/29519641.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
positive-definite kernels
reproducing kernel Hilbert space
stochastic processes
frames
machine learning
embedding problem
optimization
Opis:
Motivated by applications, we consider new operator-theoretic approaches to conditional mean embedding (CME). Our present results combine a spectral analysis-based optimization scheme with the use of kernels, stochastic processes, and constructive learning algorithms. For initially given non-linear data, we consider optimization-based feature selections. This entails the use of convex sets of kernels in a construction of optimal feature selection via regression algorithms from learning models. Thus, with initial inputs of training data (for a suitable learning algorithm), each choice of a kernel K in turn yields a variety of Hilbert spaces and realizations of features. A novel aspect of our work is the inclusion of a secondary optimization process over a specified convex set of positive definite kernels, resulting in the determination of “optimal” feature representations.
Źródło:
Opuscula Mathematica; 2024, 44, 1; 79-103
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Finitely additive functions in measure theory and applications
Autorzy:
Alpay, Daniel
Jorgensen, Palle
Powiązania:
https://bibliotekanauki.pl/articles/29519748.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
Hilbert space
reproducing kernel
probability space
Gaussian field
transforms
covariance
Itô integration
Itô calculus
generalized Brownian motion
Opis:
In this paper, we consider, and make precise, a certain extension of the Radon–Nikodym derivative operator, to functions which are additive, but not necessarily sigma-additive, on a subset of a given sigma-algebra. We give applications to probability theory; in particular, to the study of μ-Brownian motion, to stochastic calculus via generalized Itô-integrals, and their adjoints (in the form of generalized stochastic derivatives), to systems of transition probability operators indexed by families of measures μ, and to adjoints of composition operators.
Źródło:
Opuscula Mathematica; 2024, 44, 3; 323-339
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Greens functions and existence of solutions of nonlinear fractional implicit difference equations with Dirichlet boundary conditions
Autorzy:
Cabada, Alberto
Dimitrov, Nikolay D.
Jonnalagadda, Jagan Mohan
Powiązania:
https://bibliotekanauki.pl/articles/29519501.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
fractional difference
Dirichlet conditions
Green’s function
existence of solutions
Opis:
This article is devoted to deduce the expression of the Green’s function related to a general constant coefficients fractional difference equation coupled to Dirichlet conditions. In this case, due to the points where some of the fractional operators are applied, we are in presence of an implicit fractional difference equation. So, due to such a property, it is more complicated to calculate and manage the expression of the Green’s function than in the explicit case studied in a previous work of the authors. Contrary to the explicit case, where it is shown that the Green’s function is constructed as finite sums, the Green’s function constructed here is an infinite series. This fact makes necessary to impose more restrictive assumptions on the parameters that appear in the equation. The expression of the Green’s function will be deduced from the Laplace transform on the time scales of the integers. We point out that, despite the implicit character of the considered equation, we can have an explicit expression of the solution by means of the expression of the Green’s function. These two facts are not incompatible. Even more, this method allows us to have an explicit expression of the solution of an implicit problem. Finally, we prove two existence results for nonlinear problems, via suitable fixed point theorems.
Źródło:
Opuscula Mathematica; 2024, 44, 2; 167-195
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Jan Stochel, a stellar mathematician
Autorzy:
Chavan, Sameer
Curto, Raúl
Jabłoński, Zenon Jan
Jung, Il Bong
Putinar, Mihai
Powiązania:
https://bibliotekanauki.pl/articles/29519747.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
unbounded subnormal operator
moment problem
composition operator
Cauchy dual
Opis:
The occasion for this survey article was the 70th birthday of Jan Stochel, professor at Jagiellonian University, former head of the Chair of Functional Analysis and a prominent member of the Kraków school of operator theory. In the course of his mathematical career, he has dealt, among other things, with various aspects of functional analysis, single and multivariable operator theory, the theory of moments, the theory of orthogonal polynomials, the theory of reproducing kernel Hilbert spaces, and mathematical aspects of quantum mechanics.
Źródło:
Opuscula Mathematica; 2024, 44, 3; 303-321
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Local existence for a viscoelastic Kirchhoff type equation with the dispersive term, internal damping, and logarithmic nonlinearity
Autorzy:
Cordeiro, Sebastião
Raposo, Carlos
Ferreira, Jorge
Rocha, Daniel
Shahrouzi, Mohammad
Powiązania:
https://bibliotekanauki.pl/articles/29519633.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
viscoelastic equation
dispersive term
logarithmic nonlinearity
local existence
Opis:
This paper concerns a viscoelastic Kirchhoff-type equation with the dispersive term, internal damping, and logarithmic nonlinearity. We prove the local existence of a weak solution via a modified lemma of contraction of the Banach fixed-point theorem. Although the uniqueness of a weak solution is still an open problem, we proved uniqueness locally for specifically suitable exponents. Furthermore, we established a result for local existence without guaranteeing uniqueness, stating a contraction lemma.
Źródło:
Opuscula Mathematica; 2024, 44, 1; 19-47
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Local irregularity conjecture for 2-multigraphs versus cacti
Autorzy:
Grzelec, Igor
Woźniak, Mariusz
Powiązania:
https://bibliotekanauki.pl/articles/29519642.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
locally irregular coloring
decomposable
cactus graphs
2-multigraphs
Opis:
A multigraph is locally irregular if the degrees of the end-vertices of every multiedge are distinct. The locally irregular coloring is an edge coloring of a multigraph G such that every color induces a locally irregular submultigraph of G. A locally irregular colorable multigraph G is any multigraph which admits a locally irregular coloring. We denote by lir(G) the locally irregular chromatic index of a multigraph G, which is the smallest number of colors required in the locally irregular coloring of the locally irregular colorable multigraph G. In case of graphs the definitions are similar. The Local Irregularity Conjecture for 2-multigraphs claims that for every connected graph G, which is not isomorphic to K2, multigraph 2G obtained from G by doubling each edge satisfies lir(2G) ≤ 2. We show this conjecture for cacti. This class of graphs is important for the Local Irregularity Conjecture for 2-multigraphs and the Local Irregularity Conjecture which claims that every locally irregular colorable graph G satisfies lir(G) ≤ 3. At the beginning it has been observed that all not locally irregular colorable graphs are cacti. Recently it has been proved that there is only one cactus which requires 4 colors for a locally irregular coloring and therefore the Local Irregularity Conjecture was disproved.
Źródło:
Opuscula Mathematica; 2024, 44, 1; 49-65
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Möbius invariant principal functions of Pincus
Autorzy:
Ghosh, Sagar
Misra, Gadadhar
Powiązania:
https://bibliotekanauki.pl/articles/29519754.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
hyponormal operators
multiplicity
trace formula
homogeneous operators
principal function
Opis:
In this semi-expository short note, we prove that the only homogeneous pure hyponormal operator T with rank (TT − TT) = 1, modulo unitary equivalence, is the unilateral shift.
Źródło:
Opuscula Mathematica; 2024, 44, 3; 391-407
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the structure of the diffusion distance induced by the fractional dyadic Laplacian
Autorzy:
Acosta, María Florencia
Aimar, Hugo
Gómez, Ivana
Morana, Federico
Powiązania:
https://bibliotekanauki.pl/articles/29519486.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
diffusion metrics
dyadic diffusion
Opis:
In this note we explore the structure of the diffusion metric of Coifman-Lafon determined by fractional dyadic Laplacians. The main result is that, for each t > 0, the diffusion metric is a function of the dyadic distance, given in $ \mathbb{R}^+ $ by δ(x, y) = inf {|I| : I is a dyadic interval containing x and y}. Even if these functions of δ are not equivalent to δ, the families of balls are the same, to wit, the dyadic intervals.
Źródło:
Opuscula Mathematica; 2024, 44, 2; 157-165
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Parabolic turbulence k-epsilon model with applications in fluid flows through permeable media
Autorzy:
Oliveira, Hermenegildo Borges de
Powiązania:
https://bibliotekanauki.pl/articles/29519477.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
turbulence
k-epsilon modeling
permeable media
existence
Opis:
In this work, we study a one-equation turbulence k-epsilon model that governs fluid flows through permeable media. The model problem under consideration here is derived from the incompressible Navier-Stokes equations by the application of a time-averaging operator used in the k-epsilon modeling and a volume-averaging operator that is characteristic of modeling unsteady porous media flows. For the associated initial- and boundary-value problem, we prove the existence of suitable weak solutions (average velocity field and turbulent kinetic energy) in the space dimensions of physics interest.
Źródło:
Opuscula Mathematica; 2024, 44, 2; 197-240
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positive solutions for nonparametric anisotropic singular solutions
Autorzy:
Papageorgiou, Nikolaos S.
Rădulescu, Vicenţiu D.
Sun, Xueying
Powiązania:
https://bibliotekanauki.pl/articles/29519752.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
anisotropic regularity
variable Lebesgue
Sobolev spaces
anisotropic maximum principle
truncations and comparisons
Hardy inequality
Opis:
We consider an elliptic equation driven by a nonlinear, nonhomogeneous differential operator with nonstandard growth. The reaction has the combined effects of a singular term and of a “superlinear” perturbation. There is no parameter in the problem. Using variational tools and truncation and comparison techniques, we show the existence of at least two positive smooth solutions.
Źródło:
Opuscula Mathematica; 2024, 44, 3; 409-423
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positive solutions to a third order nonlocal boundary value problem with a parameter
Autorzy:
Szajnowska, Gabriela
Zima, Mirosława
Powiązania:
https://bibliotekanauki.pl/articles/29519483.pdf
Data publikacji:
2024
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
boundary value problem
nonlocal boundary conditions
positive solution
cone
Opis:
We present some sufficient conditions for the existence of positive solutions to a third order differential equation subject to nonlocal boundary conditions. Our approach is based on the Krasnosel’skiĭ-Guo fixed point theorem in cones and the properties of the Green’s function corresponding to the BVP under study. The main results are illustrated by suitable examples.
Źródło:
Opuscula Mathematica; 2024, 44, 2; 267-283
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł

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