arXiv subjects

Helena F. Gonçalves

Publications and source records attributed to Helena F. Gonçalves.

4 recordsLinked to original sources

arXiv2020

Non-smooth atomic decomposition of variable 2-microlocal Besov-type and Triebel-Lizorkin-type spaces

In this paper we provide non-smooth atomic decompositions of 2-microlocal Besov-type and Triebel-Lizorkin-type spaces with variable exponents $B^{\mathrm{\boldsymbolω}, ϕ}_{p(\cdot),q(\cdot)}(\mathbb{R}^n)$ and $F^{\mathrm{\boldsymbolω}, ϕ}_{p(\cdot),q(\cdot)}(\mathbb{R}^n)$. Of big importance in general, and an essential tool here, are the characterizations of the spaces via maximal functions and local means, that we also present. These spaces were recently introduced by Wu at al. and cover not only variable 2-microlocal Besov and Triebel-Lizorkin spaces $B^{\mathrm{\boldsymbolω}}_{p(\cdot),q(\cdot)}(\mathbb{R}^n)$ and $F^{\mathrm{\boldsymbolω}}_{p(\cdot),q(\cdot)}(\mathbb{R}^n)$, but also the more classical smoothness Morrey spaces $B^{s, τ}_{p,q}(\mathbb{R}^n)$ and $F^{s,τ}_{p,q}(\mathbb{R}^n)$. Afterwards, we state a pointwise multipliers assertion for this scale.

math.FA↗

arXiv2020

Compact embeddings in Besov-type and Triebel-Lizorkin-type Spaces on bounded domains

We study embeddings of Besov-type and Triebel-Lizorkin-type spaces, $id_τ: {B}_{p_1,q_1}^{s_1,τ_1}(Ω) \hookrightarrow {B}_{p_2,q_2}^{s_2,τ_2}(Ω)$ and $id_τ: {F}_{p_1,q_1}^{s_1,τ_1}(Ω) \hookrightarrow {F}_{p_2,q_2}^{s_2,τ_2}(Ω) $, where $Ω\subset {\mathbb R}^d$ is a bounded domain, and obtain necessary and sufficient conditions for the compactness of $id_τ$. Moreover, we characterise its entropy and approximation numbers. Surprisingly, these results are completely obtained via embeddings and the application of the corresponding results for classical Besov and Triebel-Lizorkin spaces as well as for Besov-Morrey and Triebel-Lizorkin-Morrey spaces.

math.FA↗

arXiv2017

Intrinsic atomic characterization of 2-microlocal spaces with variable exponents on domains

We provide an intrinsic atomic characterization for 2-microlocal Besov and Triebel-Lizorkin spaces with variable integrability on domains, $B_{\p,\q}^{\bm{w}}(Ω)$ and $F_{\p,\q}^{\bm{w}}(Ω)$, where $Ω$ is a regular domain. We use the already known decomposition with non-smooth atoms for the spaces $B_{\p,\q}^{\bm{w}}(\rn)$ and $F_{\p,\q}^{\bm{w}}(\rn)$ in order to get the main result.

math.FA↗

arXiv2016

Franke-Jawerth embeddings for Besov and Triebel-Lizorkin spaces with variable exponents

The classical Jawerth and Franke embeddings $$ F^{s_0}_{p_0,q}({\mathbb R}^n)\hookrightarrow B^{s_1}_{p_1,p_0}({\mathbb R}^n) \quad \mbox{and} \quad B^{s_0}_{p_0,p_1}({\mathbb R}^n)\hookrightarrow F^{s_1}_{p_1,q}({\mathbb R}^n) $$ are versions of Sobolev embedding between the scales of Besov and Triebel-Lizorkin function spaces for $s_0>s_1$ and $$ s_0-\frac{n}{p_0} = s_1-\frac{n}{p_1}.$$ We prove Jawerth and Franke embeddings for the scales of Besov and Triebel-Lizorkin spaces with all exponents variable $$ F^{s_0(\cdot)}_{p_0(\cdot),q(\cdot)}\hookrightarrow B^{s_1(\cdot)}_{p_1(\cdot),p_0(\cdot)} \quad \mbox{and} \quad B^{s_0(\cdot)}_{p_0(\cdot),p_1(\cdot)}\hookrightarrow F^{s_1(\cdot)}_{p_1(\cdot),q(\cdot)}, $$ respectively, if $\inf_{x\in\mathbb{R}^n}(s_0(x)-s_1(x))>0$ and $$ s_0(x) -\frac{n}{p_0(x)} = s_1(x) -\frac{n}{p_1(x)}, \quad x \in {\mathbb R}^n. $$ We work exclusively with the associated sequence spaces $b^{s(\cdot)}_{p(\cdot),q(\cdot)}$ and $f^{s(\cdot)}_{p(\cdot),q(\cdot)}$, which is justified by well known decomposition techniques. We give also a different proof of the Franke embedding in the constant exponent case which avoids duality arguments and interpolation. Our results hold also for 2-microlocal function spaces $B^{\mathbf{w}}_{p(\cdot),q(\cdot)}({\mathbb R}^n)$ and $F^{\mathbf{w}}_{p(\cdot),q(\cdot)}({\mathbb R}^n)$ which unify the smoothness scales of spaces of variable smoothness and generalized smoothness spaces.

math.FA↗