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Pablo Ochoa

Publications and source records attributed to Pablo Ochoa.

At least 19 recordsLinked to original sources
arXiv2026

Function spaces and potential theory in the Orlicz setting

In this article, we study certain transcendental function spaces arising in potential theory within the framework of Orlicz spaces. Specifically, we generalize Bessel and Lizorkin-Triebel spaces to the nonstandard setting of Orlicz spaces. We recover classical results from potential theory, such as the fact that Bessel-Orlicz spaces of integer order coincide with Orlicz-Sobolev spaces (Calder\'on type theorem), and we establish inclusion results for fractional orders. Moreover, we prove a Strauss-type lemma for potential spaces. In the last sections, we show that certain Orlicz-Lizorkin-Triebel spaces coincide with Bessel-Orlicz spaces, and we provide a useful atomic decomposition for these spaces.

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arXiv2026

An eigenvalue problem for a generalized polyharmonic operator in Orlicz-Sobolev spaces without the $\Delta_2$-condition

In this paper, we consider a generalized polyharmonic eigenvalue problem of the form $A(u)= \lambda h(u)$ in a bounded smooth domain with Dirichlet boundary conditions in the setting of higher-order Orlicz-Sobolev spaces. Here, $A$ is a very general operator depending on $u$ and arbitrary higher-order derivatives of $u$, whose growth is governed by an Orlicz function, and $h$ is a lower order term. Combining the theories of pseudomonotone operators with complementary systems, we prove that this eigenvalue problem has an infinite number of eigenfunctions and that the corresponding sequence of eigenvalues tends to infinity. We point out that the $\Delta_2$-condition is not assumed for the involved Orlicz functions. Finally, we prove a first regularity result for eigenfunctions by following a De Giorgi's iteration scheme.

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arXiv2025

A mixed local-nonlocal H\'enon problem in $\mathbb{R}^N$

In this article, we study a H\'enon-type equation in $\mathbb{R}^N$ driven by a nonlinear operator given by the combination of a local and a nonlocal term. This equation was originally proposed to model spherically symmetric stellar clusters. Here, we prove that, under a suitable relation among the parameters, there exists a threshold separating the existence and non-existence of solutions. Moreover, we establish regularity properties of the solutions.

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arXiv2025

The H\'enon equation in Orlicz-Sobolev spaces

In this paper, we consider the H\'enon problem in the setting of Orlicz-Sobolev spaces: \begin{equation*} \begin{cases} -\Delta_g u= |x|^\alpha h( u) \quad \text{in }B\\ u>0 \quad \text{in }B\\ u= 0 \quad \text{on }\partial B\\ \end{cases} \end{equation*}where $B$ is the unit ball in $\mathbb{R}^n$, $g=G'$, $h=H'$ are N-functions and the operator $-\Delta_g$ is the $g$-Laplacian. We show that the symmetric term $|x|^\alpha$, for $\alpha>0$, allows to have radial solutions even for supercritical $H$, generalizing results for the classical H\'enon equation. We also show that radial solutions are indeed bounded. Finally, we state a Pohozaev's identity in Orlicz-Sobolev spaces that we apply to get a range in $\alpha$ for which the problem has no bounded solutions.

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arXiv2025

Elliptic systems in Orlicz-Sobolev spaces with critical sources in bounded domains

In this paper, we show the existence of non-trivial solutions to very general elliptic systems with critical non-linearities in the sense of embeddings in Orlicz-Sobolev spaces. This allows to consider non-linearities which do not have polynomial growth. To achieve the existence, we combine a Mountain Pass Theorem without the Palais-Smale condition with the second Concentration Compactness Principle of Lions in Orlicz-Sobolev spaces.

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arXiv2024

Hopf's lemmas and boundary behaviour of solutions to the fractional Laplacian in Orlicz-Sobolev spaces

In this article we study different extensions of the celebrated Hopf's boundary lemma within the context of a family of nonlocal, nonlinear and nonstandard growth operators. More precisely, we examine the behavior of solutions of the fractional $a-$Laplacian operator near the boundary of a domain satisfying the interior ball condition. Our approach addresses problems involving both constant-sign and sign-changing potentials.

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arXiv2024

Existence of weak solutions for the anisotropic $p(x)$-Laplacian via degree theory

In this paper, we consider Dirichlet boundary value problem involving the anisotropic $p(x)$-Laplacian, where $p(x)= (p_1(x), ..., p_n(x))$, with $p_i(x)> 1$ in $\overline{\Omega}$. Using the topological degree constructed by Berkovits, we prove, under appropriate assumptions on the data, the existence of weak solutions for the given problem. An important contribution is that we are considering the degenerate and the singular cases in the discussion. Finally, according to the compact embedding for anisotropic Sobolev spaces, we point out that the considered boundaru value problem may be critical in some region of $\Omega$.

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arXiv2024

Nonlinear eigenvalue problems for a biharmonic operator in Orlicz-Sobolev spaces

In this paper, we introduce a new higher-order Laplacian operator in the framework of Orlicz-Sobolev spaces, the biharmonic g-Laplacian $$\Delta_g^2 u:=\Delta \left(\dfrac{g(|\Delta u|)}{|\Delta u|} \Delta u\right),$$ where $g=G'$, with $G$ an N-function. This operator is a generalization of the so called bi-harmonic Laplacian $\Delta^2$. Here, we also established basic functional properties of $\Delta_g^2$, which can be applied to existence results. Afterwards, we study the eigenvalues of $\Delta_g^2$, which depend on normalisation conditions, due to the lack of homogeneity of the operator. Finally, we study different nonlinear eigenvalue problems associated to $\Delta_g^2$ and we show regimes where the corresponding spectrum concentrate at $0$, $\infty$ or coincide with $(0, \infty)$.

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arXiv2023

Hopf's lemmas and boundary point results for the fractional $p$-Laplacian

In this paper, we consider different versions of the classical Hopf's boundary lemma in the setting of the fractional $p-$Laplacian for $p \geq 2$. We start by providing for a new proof to a Hopf's lemma based on comparison principles. Afterwards, we give a Hopf's result for sign-changing potential describing the behavior of the fractional normal derivative of solutions around boundary points. The main contribution here is that we do not need to impose a global condition on the sign of the solution. Applications of the main results to boundary point lemmas and non-local non-linear overdetermined problems are also provided.

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arXiv2023

Higher-order asymptotic expansions and finite difference schemes for the fractional $p$-Laplacian

We propose a new asymptotic expansion for the fractional $p$-Laplacian with precise computations of the errors. Our approximation is shown to hold in the whole range $p\in(1,\infty)$ and $s\in(0,1)$, with errors that do not degenerate as $s\to1^-$. These are super-quadratic for a wide range of $p$ (better far from the zero gradient points), and optimal in most cases. One of the main ideas here is the fact that the singular part of the integral representation of the fractional $p$-Laplacian behaves like a local $p$-Laplacian with a weight correction. As a consequence of this, we also revisit a previous asymptotic expansion for the classical $p$-Laplacian, whose error orders were not known. Based on the previous result, we propose monotone finite difference approximations of the fractional $p$-Laplacian with explicit weights and we obtain the error estimates. Finally, we introduce explicit finite difference schemes for the associated parabolic problem in $\mathbb{R}^d$ and show that it is stable, monotone and convergent in the context of viscosity solutions. An interesting feature is the fact that the stability condition improves with the regularity of the initial data.

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arXiv2022

Existence and multiplicity of solutions to magnetic Kirchhoff equations in Orlicz-Sobolev spaces

In this paper, we study the existence and multiplicity of weak solutions to a general type of Kirchhoff equations in magnetic fractional Orlicz-Sobolev spaces. Specifically, we appeal to Critical Point Theory to prove the existence of non-trivial solutions under the so-called Ambrosetti-Rabinowitz condition. We also state the existence of ground-state solutions. Moreover, multiplicity results which yield the existence of an unbounded sequence of solutions are also provided. Finally, we show existence under a weak-type Ambrosetti-Rabinowitz condition formulated in the framework of Orlicz spaces.

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arXiv2021

Existence and multiplicity of solutions for a Dirichlet problem in Fractional Orlicz- Sobolev spaces

In this paper, we first prove the existence of solutions to Dirichlet problems involving the fractional $g$-Laplacian operator and lower order terms by appealing to sub- and supersolution methods. Moreover, we also state the existence of extremal solutions. Afterwards, and under additional assumptions on the lower order structure, we establish by variational techniques the existence of multiple solutions: one positive, one negative and one with non-constant sign.

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arXiv2021

Equivalence of solutions for non-homogeneous p(x)-Laplace equations

We establish the equivalence between weak and viscosity solutions for non-homogeneous $p(x)$-Laplace equations with a right-hand side term depending on the spatial variable, the unknown, and its gradient. We employ inf- and sup-convolution techniques to state that viscosity solutions are also weak solutions, and comparison principles to prove the converse. The new aspects of the $p(x)$-Laplacian compared to the constant case are the presence of $\log$-terms and the lack of the invariance under translations.

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arXiv2021

Weak and viscosity solutions for non-homogeneous fractional equations in Orlicz spaces

In this paper, we consider non-homogeneous fractional equations in Orlicz spaces, with a source depending on the spatial variable, the unknown function, and its fractional gradient. The latter is adapted to the Orlicz framework. The main contribution of the article is to establish the equivalence between weak and viscosity solutions for such equations.

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arXiv2020

A note on quasilinear equations with fractional diffusion

In this paper, we study the existence of distributional solutions of the following non-local elliptic problem \begin{eqnarray*} \left\lbrace \begin{array}{l} (-Δ)^{s}u + |\nabla u|^{p} =f \quad\text{ in } Ω \qquad \qquad \qquad \,\,\, u=0 \,\,\,\,\,\,\,\text{ in } \mathbb{R}^{N}\setminus Ω, \quad s \in (1/2, 1). \end{array} \right. \end{eqnarray*} We are interested in the relation between the regularity of the source term $f$, and the regularity of the corresponding solution. If $p<2s$, that is the natural growth, we are able to show the existence for all $f\in L^1(Ø)$. In the subcritical case, that is, for $p < p_{*}:=N/(N-2s+1)$, we show that solutions are $\mathcal{C}^{1, α}$ for $f \in L^{m}$, with $m$ large enough. In the general case, we achieve the same result under a condition on the size of the source. As an application, we may show that for regular sources, distributional solutions are viscosity solutions, and conversely.

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arXiv2020

Fractional elliptic problems with nonlinear gradient sources and measures

In this manuscript we deal with existence/uniqueness and regularity issues of suitable weak solutions to nonlocal problems driven by fractional Laplace type operators. Different from previous researches, in our approach we consider gradient non-linearity sources with subcritical growth, as well as appropriated measures as sources and boundary datum. We provide an in-depth discussion on the notions of solutions involved together with existence/uniqueness results in different regimes and for different boundary value problems. Finally, this work extends previous ones by dealing with more general nonlocal operators, source terms and boundary data.

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arXiv2020

Regularity for degenerate evolution equations with strong absorption

In this manuscript, we study geometric regularity estimates for degenerate parabolic equations of $p$-Laplacian type ($2 \leq p< \infty$) under a strong absorption condition: $ Δ_p u - \frac{\partial u}{\partial t} = λ_0 u_{+}^q \quad \mbox{in} \quad Ω_T \defeq Ω\times (0, T), $ where $0 \leq q < 1$ and $λ_0$ is a function bounded away from zero and infinity. This model is interesting because it yields the formation of dead-core sets, i.e, regions where non-negative solutions vanish identically. We shall prove sharp and improved parabolic $C^α$ regularity estimates along the set $\mathfrak{F}_0(u, Ω_T) = \partial \{u>0\} \cap Ω_T$ (the free boundary), where $α= \frac{p}{p-1-q}\geq 1+\frac{1}{p-1}$. Some weak geometric and measure theoretical properties as non-degeneracy, positive density, porosity and finite speed of propagation are proved. As an application, we prove a Liouville-type result for entire solutions provided their growth at infinity can be appropriately controlled. A specific analysis for Blow-up type solutions will be done as well. The results obtained in this article via our approach are new even for dead-core problems driven by the heat operator.

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