Almost everywhere convergence of Bochner-Riesz means for the Hermite type Laguerre expansions

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Abstract

Consider the space $\mathbb{R}_+^d=(0,\infty)^d$ equipped with Euclidean distance and the Lebesgue measure. For every $\alpha=(\alpha_1,...,\alpha_d)\in[-1/2,\infty)^d$, we consider the Hermite-Laguerre operator $\mathcal{L}^\alpha=-\Delta+\arrowvert x\arrowvert^2+\sum_{i=1}^{d}(\alpha_j^2-\frac{1}{4})\frac{1}{x_i^2}$. In this paper we study almost everywhere convergence of the Bochner-Riesz means associated with $\mathcal{L}^\alpha$ which is defined as $S_R^{\lambda}(\mathcal{L}^\alpha)f(x)=\sum_{n=0}^{\infty}(1-\frac{4n+2\arrowvert\alpha\arrowvert_1+2d}{R^2})_{+}^{\lambda}\mathcal{P}_nf(x)$. Here $\mathcal{P}_nf(x)$ is the n-th Laguerre spectral projection operator and $\arrowvert\alpha\arrowvert_1$ denotes $\sum_{i=1}^{d}\alpha_i$. For $2\leq p<\infty$, we prove that \[ \lim_{R \to \infty} S_R^{\lambda}(\mathcal{L}^\alpha)f = f \quad \text{a.e.} \] for all $f\in L^p({\mathbb{R}_+^d})$ provided that $\lambda>\lambda(p)/2$ and $\lambda(p)=\max\{d(1/2-1/p)-1/2,0\}$. Conversely, we show that the convergence generally fails if $\lambda<\lambda(p)/2$ in the sense that there exists $f\in L^p({\mathbb{R}_+^d})$ for $2d/(d-1)< p$ such that the convergence fails.