arXiv subjects
Publications and source records attributed to Jorge J. Betancor.
We consider the Weinstein type equation $\mathcal{L}_λu=0$ on $(0,\infty )\times (0,\infty )$, where $\mathcal{L}_λ=\partial _t^2+\partial _x^2-\frac{λ(λ-1)}{x^2}$, with $λ>1$. In this paper we characterize the solutions of $\mathcal{L}_λu=0$ on $(0,\infty )\times(0,\infty )$ representable by Bessel-Poisson integrals of BMO-functions as those ones satisfying certain Carleson properties.
In this paper we consider conical square functions in the Bessel, Laguerre and Schrödinger settings where the functions take values in UMD Banach spaces. Following a recent paper of Hytönen, van Neerven and Portal, in order to define our conical square functions, we use $γ$-radonifying operators. We obtain new equivalent norms in the Lebesgue-Bochner spaces $L^p((0,\infty ),\mathbb{B})$ and $L^p(\mathbb{R}^n,\mathbb{B})$, $1<p<\infty$, in terms of our square functions, provided that $\mathbb{B}$ is a UMD Banach space. Our results can be seen as Banach valued versions of known scalar results for square functions.
We establish that the spectral multiplier $\frak{M}(G_α)$ associated to the differential operator $$ G_α=- Δ_x +\sum_{j=1}^m{{α_j^2-1/4}\over{x_j^2}}-|x|^2 Δ_y \; \text{on} (0,\infty)^m \times \R^n,$$ which we denominate Bessel-Grushin operator, is of weak type $(1,1)$ provided that $\frak{M}$ is in a suitable local Sobolev space. In order to do this we prove a suitable weighted Plancherel estimate. Also, we study $L^p$-boundedness properties of Riesz transforms associated to $G_α$, in the case $n=1$.
In this paper we prove that the maximal $L^p$-regularity property on the interval $(0,T)$, $T>0$, for Cauchy problems associated with the square root of Hermite, Bessel or Laguerre type operators on $L^2(Ω, dμ; X),$ characterizes the UMD property for the Banach space $X$.
In this paper we consider square functions (also called Littlewood-Paley g-functions) associated to Hankel convolutions acting on functions in the Bochner-Lebesgue space $L^p((0,\infty),B)$, where $B$ is a UMD Banach space. As special cases we study square functions defined by fractional derivatives of the Poisson semigroup for the Bessel operator $Δ_λ=-x^{-λ}\frac{d}{dx}x^{2λ}\frac{d}{dx}x^{-λ}$, $λ>0$. We characterize the UMD property for a Banach space $B$ by using $L^p((0,\infty),B)$-boundedness properties of g-functions defined by Bessel-Poisson semigroups. As a by product we prove that the fact that the imaginary power $Δ_λ^{iw}$, $w\in \mathbb{R}\setminus\{0\}$, of the Bessel operator $Δ_λ$ is bounded in $L^p ((0,\infty),B)$, $1<p<\infty$, characterizes the UMD property for the Banach space $B$. As applications of our results for square functions we establish the boundedness in $L^p((0,\infty),B)$ of spectral multipliers $m(Δ_λ)$ of Bessel operators defined by functions $m$ which are holomorphic in sectors $Σ_\vartheta$.
In this paper we study Littlewood-Paley-Stein functions associated with the Poisson semigroup for the Hermite operator on functions with values in a UMD Banach space $\B.$ If we denote by $H$ the Hilbert space $L^2((0,\infty),dt/t),γ(H,\B)$ represents the space of $γ$-radonifying operators from $H$ into $\B.$ We prove that the Hermite square function defines bounded operators from $BMO_\mathcal{L}(\R,\B)$ (respectively, $H^1_\mathcal{L}(\R, \B)$) into $BMO_\mathcal{L}(\R,γ(H,\B))$ (respectively, $H^1_\mathcal{L}(\R, γ(H,\B))$), where $BMO_\mathcal{L}$ and $H^1_\mathcal{L}$ denote $BMO$ and Hardy spaces in the Hermite setting. Also, we obtain equivalent norms in $BMO_\mathcal{L}(\R, \B)$ and $H^1_\mathcal{L}(\R,\B)$ by using Littlewood-Paley-Stein functions. As a consequence of our results, we establish new characterizations of the UMD Banach spaces.
In this paper we characterize the Lebesgue Bochner spaces $L^p(\mathbb{R}^n,B)$, $1<p<\infty$, by using Littlewood-Paley $g$-functions in the Hermite setting, provided that $B$ is a UMD Banach space. We use $γ$-radonifying operators $γ(H,B)$ where $H=L^2((0,\infty),\frac{dt}{t})$. We also characterize the UMD Banach spaces in terms of $L^p(\mathbb{R}^n,B)$-$L^p(\mathbb{R}^n,γ(H,B))$ boundedness of Hermite Littlewood-Paley $g$-functions.
In this paper we prove that the generalized (in the sense of Caffarelli and Calderón) maximal operators associated with heat semigroups for Bessel and Laguerre operators are weak type (1,1). Our results include other known ones and our proofs are simpler than the ones for the known special cases.
In this paper we consider the space $BMO_o(\mathbb{R},X)$ of bounded mean oscillations and odd functions on $\mathbb{R}$ taking values in a UMD Banach space $X$. The functions in $BMO_o(\mathbb{R},X)$ are characterized by Carleson type conditions involving Bessel convolutions and $γ$-radonifying norms. Also we prove that the UMD Banach spaces are the unique Banach spaces for which certain $γ$-radonifying Carleson inequalities for Bessel-Poisson integrals of $BMO_o(\mathbb{R},X)$ functions hold.
In this paper we obtain new characterizations of the q-uniformly convex and smooth Banach spaces by using Carleson measures. These measures are defined by Poisson integral associated with Bessel operators and Banach valued BMO-functions. By the way we describe q-uniformly convexity and smoothness of a Banach space in terms of the mapping properties of the Lusin integral defined by the Poisson semigroup for Bessel operators.
In this paper we characterize the Banach spaces with the UMD property by means of Lp-boundedness properties for the imaginary powers of the Hermite and Laguerre operators. In order to do this we need to obtain pointwise representations for the Laplace transform type multipliers associated with Hermite and Laguerre operators.
We study several fundamental operators in harmonic analysis related to Bessel operators, including maximal operators related to heat and Poisson semigroups, Littlewood-Paley-Stein square functions, multipliers of Laplace transform type and Riesz transforms. We show that these are (vector-valued) Calderón-Zygmund operators in the sense of the associated space of homogeneous type, and hence their mapping properties follow from the general theory.
In this paper we represent the $k$-th Riesz transform in the ultraspherical setting as a principal value integral operator for every $k\in \mathbb{N}$. We also measure the speed of convergence of the limit by proving $L^p$-boundedness properties for the oscillation and variation operators associated with the corresponding truncated operators.
In this paper we investigate Lp-boundedness properties for the higher order Riesz transforms associated with Laguerre operators. Also we prove that the k-th Riesz transform is a principal value singular integral operator (modulus a constant times of the function when k is even). To establish our results we exploit a new identity connecting Riesz transforms in the Hermite and Laguerre settings.
We prove sharp power-weighted strong type, weak type and restricted weak type inequalities for the heat and Poisson integral maximal operators, Riesz transform and a Littlewood-Paley type square function, emerging naturally in the harmonic analysis related to Bessel operators.