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J. J. Betancor

Publications and source records attributed to J. J. Betancor.

17 recordsLinked to original sources

Pointwise convergence of the heat and subordinates of the heat semigroups associated with the Laplace operator on homogeneous trees and two weighted $L^p$ maximal inequalities

In this paper we consider the heat semigroup $\{W_t\}_{t>0}$ defined by the combinatorial Laplacian and two subordinated families of $\{W_t\}_{t>0}$ on homogeneous trees $X$. We characterize the weights $u$ on $X$ for which the pointwise convergence to initial data of the above families holds for every $f\in L^{p}(X,μ,u)$ with $1\le p<\infty$, where $μ$ represents the counting measure in $X$ . We prove that this convergence property in $X$ is equivalent to the fact that the maximal operator on $t\in (0,R)$, for some $R>0$, defined by the semigroup is bounded from $L^{p}(X,μ,u)$ into $L^{p}(X,μ,v)$ for some weight $v$ on $X$.

math.AP↗

BLO spaces associated with Laguerre polynomials expansions

In this paper we introduce spaces of $\textup{BLO}$-type related to Laguerre polynomial expansions. We consider the probability measure on $(0,\infty)$ defined by $dγ_α(x)=\frac{2}{Γ(α+1)}e^{-x^2}x^{2α+1}dx$ with $α>-\frac12$. For every $a>0$, the space $\textup{BLO}_a((0,\infty),γ_α)$ consists of all those measurable functions defined on $(0,\infty)$ having bounded lower oscillation with respect to $γ_α$ over an admissible family $\mathcal{B}_a$ of intervals in $(0,\infty)$. The space $\textup{BLO}_a((0,\infty),γ_α)$ is a subspace of the space $\textup{BMO}_a((0,\infty),γ_α)$ of bounded mean oscillation functions with respect to $γ_α$ and $\mathcal{B}_a$. The natural $a$-local centered maximal function defined by $γ_α$ is bounded from $\textup{BMO}_a((0,\infty),γ_α)$ into $\textup{BLO}_a((0,\infty),γ_α)$. We prove that the maximal operator, the $ρ$-variation and the oscillation operators associated with local truncations of the Riesz transforms in the Laguerre setting are bounded from $L^\infty((0,\infty),γ_α)$ into $\textup{BLO}_a((0,\infty),γ_α)$. Also, we obtain a similar result for the maximal operator of local truncations for spectral Laplace transform type multipliers.

math.AP↗

Littlewood-Paley-Stein theory and Banach spaces in the inverse Gaussian setting

In this paper we consider Littlewood-Paley functions defined by the semigroups associated with the operator $\mathcal{A}=-\fracΔ{2}-x\nabla$ in the inverse Gaussian setting for Banach valued functions. We characterize the uniformly convex and smooth Banach spaces by using $L^p(\mathbb{R}^n,γ_{-1})$- properties of the $\mathcal{A}$-Littlewood-Paley functions. We also use Littlewood-Paley functions associated with $\mathcal{A}$ to characterize the Köthe function spaces with the UMD property.

math.CA↗

Anisotropic Hardy-Lorentz spaces with variable exponents

In this paper we introduce Hardy-Lorentz spaces with variable exponents associated to dilation in ${\Bbb R}^n$. We establish maximal characterizations and atomic decompositions for our variable exponent anisotropic Hardy-Lorentz spaces.

math.FA↗

Vector valued multivariate spectral multipliers, Littlewood-Paley functions, and Sobolev spaces in hte Hermite setting

In this paper we find new equivalent norms in $L^p(\mathbb{R}^n,\mathbb{B})$ by using multivariate Littlewood-Paley functions associated with Poisson semigroup for the Hermite operator, provided that $\mathbb{B}$ is a UMD Banach space with the property ($α$). We make use of $γ$-radonifying operators to get new equivalent norms that allow us to obtain $L^p(\mathbb{R}^n,\mathbb{B})$-boundedness properties for (vector valued) multivariate spectral multipliers for Hermite operators. As application of this Hermite multiplier theorem we prove that the Banach valued Hermite Sobolev and potential spaces coincide.

math.CA↗

The fractional Bessel equation in Hölder spaces

Motivated by the Poisson equation for the fractional Laplacian on the whole space with radial right hand side, we study global Hölder and Schauder estimates for a fractional Bessel equation. Our methods stand on the so-called semigroup language. Indeed, by using the solution to the Bessel heat equation we derive pointwise formulas for the fractional operators. Appropriate Hölder spaces, which can be seen as Campanato-type spaces, are characterized through Bessel harmonic extensions and fractional Carleson measures. From here the regularity estimates for the fractional Bessel equations follow. In particular, we obtain regularity estimates for radial solutions to the fractional Laplacian.

math.AP↗

UMD-valued square functions associated with Bessel operators in Hardy and BMO spaces

We consider Banach valued Hardy and BMO spaces in the Bessel setting. Square functions associated with Poisson semigroups for Bessel operators are defined by using fractional derivatives. If B is a UMD Banach space we obtain for B-valued Hardy and BMO spaces equivalent norms involving $γ$-radonifying operators and square functions. We also establish characterizations of UMD Banach spaces by using Hardy and BMO-boundedness properties of g-functions associated to Bessel-Poisson semigroup.

math.CA↗

UMD Banach spaces and square functions associated with heat semigroups for Schrödinger and Laguerre operators

In this paper we define square functions (also called Littlewood-Paley-Stein functions) associated with heat semigroups for Schrödinger and Laguerre operators acting on functions which take values in UMD Banach spaces. We extend classical (scalar) L^p-boundedness properties for the square functions to our Banach valued setting by using γ-radonifying operators. We also prove that these L^p-boundedness properties of the square functions actually characterize the Banach spaces having the UMD property.

math.CA↗

Multipliers and imaginary powers of the schrödinger operators characterizing UMD Banach spaces

In this paper we establish $L^p$-boundedness properties for Laplace type transform spectral multipliers associated with the Schrödinger operator $\mathcal{L}=-Δ+V$. We obtain for this type of multipliers pointwise representation as principal value integral operators. We also characterize the UMD Banach spaces in terms of the $L^p$-boundedness of the imaginary powers $\mathcal{L}^{iγ}$, $γ\in \mathbb{R}$, of $\mathcal{L}$.

math.CA↗

A T1 criterion for Hermite-Calderon-Zygmund operators on the BMO_H(R^n) space and applications

In this paper we establish a T1 criterion for the boundedness of Hermite-Calderon-Zygmund operators on the BMO_H(R^n) space naturally associated to the Hermite operator H. We apply this criterion in a systematic way to prove the boundedness on BMO_H(R^n) of certain harmonic analysis operators related to H (Riesz transforms, maximal operators, Littlewood-Paley g-functions and variation operators).

math.CA↗

Hankel Multipliers of Laplace Transform Type

In this paper we prove that the Hankel multipliers of Laplace transform type on $(0,1)^n$ are of weak type (1,1). Also we analyze Lp-boundedness properties for the imaginary powers of Bessel operator on $(0,1)^n$.

math.CA↗

Harmonic Analysis Operators Associated with Multidimensional Bessel Operators

In this paper we establish that the maximal operator and the Littlewood-Paley g-function associated with the heat semigroup defined by multidimensional Bessel operators are of weak type (1,1). Also, we prove that Riesz transforms in the multidimensional Bessel setting are of strong type (p,p), for every $1<p<\infty$, and of weak type (1,1).

math.CA↗

Heat and Poisson semigroups for Fourier-Neumann expansions

Given $α> -1$, consider the second order differential operator in $(0,\infty)$, $$L_αf \equiv (x^2 \frac{d^2}{dx^2} + (2α+3)x \frac{d}{dx} + x^2 + (α+1)^2)(f), $$ which appears in the theory of Bessel functions. The purpose of this paper is to develop the corresponding harmonic analysis taking $L_α$ as the analogue to the classical Laplacian. Namely we study the boundedness properties of the heat and Poisson semigroups. These boundedness properties allow us to obtain some convergence results that can be used to solve the Cauchy problem for the corresponding heat and Poisson equations.

math.FA↗