arXiv subjects

Ireneo Peral

Publications and source records attributed to Ireneo Peral.

At least 19 recordsLinked to original sources

arXiv2021

On the KPZ equation with fractional diffusion: global regularity and existence results

In this work we analyze the existence of solutions to the fractional quasilinear problem, $$ (P) \left\{ \begin{array}{rcll} u_t+(-Δ)^s u &=&|\nabla u|^α+ f &\inn Ω_T\equivΩ\times (0,T),\\ u(x,t)&=&0 & \inn(\mathbb{R}^N\setminusΩ)\times [0,T),\\ u(x,0)&=&u_{0}(x) & \innΩ,\\ \end{array}\right. $$ where $Ω$ is a $C^{1,1}$ bounded domain in $\mathbb{R}^N$, $N> 2s$ and $\frac{1}{2} \dfrac{1}{1-s}$. This behavior clearly exhibits a deep difference with the local case.

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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

Towards a deterministic KPZ equation with fractional diffusion: The stationary problem

In this work we analyze the existence of solution to the fractional quasilinear problem, \begin{equation*} \left\{ \begin{array}{rcll} (-Δ)^s u &= & |\nabla u|^{p}+ łf & \text{ in }Ω, u &=& 0 &\hbox{ in } \mathbb{R}^N\setminusΩ, u&>&0 &\hbox{ in }Ω, \end{array}% \right. \end{equation*}% where $Ω\subset \ren$ is a bounded regular domain ($\mathcal{C}^2$ is sufficient), $s\in (\frac 12, 1)$, $1 2s$.

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arXiv2020

Fractional KPZ equations with critical growth in the gradient respect to Hardy potential

In this work we study the existence of positive solution to the fractional quasilinear problem, $$ \left\{ \begin{array}{rcll} (-Δ)^s u &=&λ\dfrac{u}{|x|^{2s}}+ |\nabla u|^{p}+ μf &\inn Ω,\\ u&>&0 & \innΩ,\\ u&=&0 & \inn(\mathbb{R}^N\setminusΩ), \end{array}\right. $$ where $Ω$ is a $C^{1,1}$ bounded domain in $\mathbb{R}^N$, $N> 2s, μ>0$, $\frac{1}{2} 0$, there exists a critical exponent $p_{+}(λ, s)$ such that for $p> p_{+}(λ,s)$ there is no positive solution. Moreover, $p_{+}(λ,s)$ is optimal in the sense that, if $p<p_{+}(λ,s)$ there exists a positive solution for suitable data and $μ$ sufficiently small.

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arXiv2019

A note on the Fujita exponent in Fractional heat equation involving the Hardy potential

In this work, we are interested on the study of the Fujita exponent and the meaning of the blow-up for the Fractional Cauchy problem with the Hardy potential, namely, \begin{equation*} u_t+(-Δ)^s u=λ\dfrac{u}{|x|^{2s}}+u^{p}\inn\ren,\\ u(x,0)=u_{0}(x)\inn\ren, \end{equation*} where $N> 2s$, $0 0$, $u_0\ge 0$, and $1<p<p_{+}(s,λ)$, where $p_{+}(λ, s)$ is the critical existence power found in \cite{BMP} and \cite{AMPP}.

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arXiv2017

Attainability of the fractional Hardy constant with nonlocal mixed boundary conditions. Applications

The first goal of this paper is to study necessary and sufficient conditions to obtain the attainability of the \textit{fractional Hardy inequality } $$Λ_{N}\equivΛ_{N}(Ω):=\inf_{\{ϕ\in \mathbb{E}^s(Ω, D), ϕ\neq 0\}} \dfrac{\frac{a_{d,s}}{2} \displaystyle\int_{\mathbb{R}^d} \int_{\mathbb{R}^d} \dfrac{|ϕ(x)-ϕ(y)|^2}{|x-y|^{d+2s}}dx dy} {\displaystyle\int_Ω\frac{ϕ^2}{|x|^{2s}}\,dx}, $$ where $Ω$ is a bounded domain of $\mathbb{R}^d$, $0 & 0 &{\text{ in }} Ω, \mathcal{B}_{s}u&:=&uχ_{D}+\mathcal{N}_{s}uχ_{N}=0 &{\text{ in }}\mathbb{R}^{d}\backslash Ω, \\ \end{array}\right. $$ with $N$ and $D$ open sets in $\mathbb{R}^d\backslashΩ$ such that $N \cap D=\emptyset$ and $\overline{N}\cup \overline{D}= \mathbb{R}^d \backslashΩ$, $d>2s$, $λ> 0$ and $0<p\le 2_s^*-1$, $2_s^*=\frac{2d}{d-2s}$. We emphasize that the nonlinear term can be critical. The operators $(-Δ)^s $, fractional laplacian, and $\mathcal{N}_{s}$, nonlocal Neumann condition, are defined below in (1.5) and (1.6) respectively.

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arXiv2017

Principal Eigenvalue of Mixed Problem for the Fractional Laplacian: Moving the Boundary Conditions

We analyze the behavior of the eigenvalues of the following non local mixed problem $\left\{ \begin{array}{rcll} (-Δ)^{s} u &=& λ_1(D) \ u &\innΩ,\\ u&=&0&\inn D,\\ \mathcal{N}_{s}u&=&0&\inn N. \end{array}\right $ Our goal is to construct different sequences of problems by modifying the configuration of the sets $D$ and $N$, and to provide sufficient and necessary conditions on the size and the location of these sets in order to obtain sequences of eigenvalues that in the limit recover the eigenvalues of the Dirichlet or Neumann problem. We will see that the non locality plays a crucial role here, since the sets $D$ and $N$ can have infinite measure, a phenomenon that does not appear in the local case (see for example \cite{D,D2,CP}).

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arXiv2016

On fractional p-laplacian parabolic problem with general data

In this article the problem to be studied is the following $$ (P) \left\{ \begin{array}{rcll} u_t+(-\D^s_{p}) u & = & f(x,t) & \text{ in } Ø_{T}\equiv Ω\times (0,T), \\ u & = & 0 & \text{ in }(\ren\setminusØ) \times (0,T), \\ u & \ge & 0 & \text{ in }\ren \times (0,T),\\ u(x,0) & = & u_0(x) & \mbox{ in }Ø, \end{array}% \right. $$ where $Ω$ is a bounded domain, and $(-\D^s_{p})$ is the fractional p-Laplacian operator defined by $$ (-\D^s_{p})\, u(x,t):=P.V\int_{\ren} \,\dfrac{|u(x,t)-u(y,t)|^{p-2}(u(x,t)-u(y,t))}{|x-y|^{N+ps}} \,dy$$ with $1<p<N$, $s\in (0,1)$ and $f, u_0$ are measurable functions. The main goal of this work is to prove that if $(f,u_0)\in L^1(Ø_T)\times L^1(Ø)$, problem $(P)$ has a weak solution with suitable regularity. In addition, if $f_0, u_0$ are nonnegative, we show that the problem above has a nonnegative entropy solution. In the case of nonnegative data, we give also some quantitative and qualitative properties of the solution according the values of $p$.

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arXiv2016

Bifurcation results for a fractional elliptic equation with critical exponent in R^n

In this paper we study some nonlinear elliptic equations in $\R^n$ obtained as a perturbation of the problem with the fractional critical Sobolev exponent, that is $$ (-Δ)^s u = ε\,h\,u^q + u^p \ {in}\R^n,$$ where $s\in(0,1)$, $n>4s$, $ε>0$ is a small parameter, $p=\frac{n+2s}{n-2s}$, $0<q<p$ and $h$ is a continuous and compactly supported function. To construct solutions to this equation, we use the Lyapunov-Schmidt reduction, that takes advantage of the variational structure of the problem. For this, the case $0<q<1$ is particularly difficult, due to the lack of regularity of the associated energy functional, and we need to introduce a new functional setting and develop an appropriate fractional elliptic regularity theory.

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arXiv2015

The effect of the Hardy potential in some Calderón-Zygmund properties for the fractional Laplacian

The goal of this paper is to study the effect of the Hardy potential on the existence and summability of solutions to a class of nonlocal elliptic problems $$ \left\{\begin{array}{rcll} (-Δ)^s u-λ\dfrac{u}{|x|^{2s}}&=&f(x,u) &\hbox{ in } Ω,\\ u&=&0 &\hbox{ in } \mathbb{R}^N\setminusΩ,\\ u&>&0 &\hbox{ in }Ω, \end{array}\right. $$ where $(-Δ)^s$, $s\in(0,1)$, is the fractional laplacian operator, $Ω\subset \mathbb{R}^N$ is a bounded domain with Lipschitz boundary such that $0\inΩ$ and $N>2s$. We will mainly consider the solvability in two cases: 1) The linear problem, that is, $f(x,t)=f(x)$, where according to the summability of the datum $f$ and the parameter $λ$ we give the summability of the solution $u$. 2) The problem with a nonlinear term $f(x,t)=\frac{h(x)}{t^σ}$ for $t>0$. In this case, existence and regularity will depend on the value of $σ$ and on the summability of $h$. Looking for optimal results we will need a weak Harnack inequality for elliptic operators with \emph{singular coefficients} that seems to be new.

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arXiv2015

Optimal results for the fractional heat equation involving the Hardy potential

In this paper we study the influence of the Hardy potential in the fractional heat equation. In particular, we consider the problem $$(P_θ)\quad \left\{ \begin{array}{rcl} u_t+(-Δ)^{s} u&=&ł\dfrac{\,u}{|x|^{2s}}+θu^p+ c f\mbox{ in } Ω\times (0,T),\\ u(x,t)&>&0\inn Ω\times (0,T),\\ u(x,t)&=&0\inn (\ren\setminusΩ)\times[ 0,T),\\ u(x,0)&=&u_0(x) \mbox{ if }x\inØ, \end{array} \right. $$ where $N> 2s$, $0 1$, $c,ł>0$, $u_0\ge 0$, $f\ge 0$ are in a suitable class of functions and $θ=\{0,1\}$. Notice that $(P_0)$ is a linear problem, while $(P_1)$ is a semilinear problem. The main features in the article are: \begin{enumerate} \item Optimal results about \emph{existence} and \emph{instantaneous and complete blow up} in the linear problem $(P_0)$, where the best constant $Λ_{N,s}$ in the fractional Hardy inequality provides the threshold between existence and nonexistence. Similar results in the local heat equation were obtained by Baras and Goldstein in \cite{BaGo}. However, in the fractional setting the arguments are much more involved and they require the proof of a weak Harnack inequality for a weighted operator that appear in a natural way. Once this Harnack inequality is obtained, the optimal results follow as a simpler consequence than in the classical case. \item The existence of a critical power $p_+(s,λ)$ in the semilinear problem $(P_1)$ such that: \begin{enumerate} \item If $p> p_+(s,λ)$, the problem has no weak positive supersolutions and a phenomenon of \emph{complete and instantaneous blow up} happens. \item If $p< p_+(s,λ)$, there exists a positive solution for a suitable class of nonnegative data. \end{enumerate} \end{enumerate}

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arXiv2015

Qualitative properties of positive solutions to nonlocal critical problems involving the Hardy-Leray potential

We prove the existence, qualitative properties and asymptotic behavior of positive solutions to the doubly critical problem $$ (-Δ)^s u=\vartheta\frac{u}{|x|^{2s}}+u^{2_s^*-1}, \quad u\in \dot{H}^s(\mathbb{R}^N).$$ The technique that we use to prove the existence is based on variational arguments. The qualitative properties are obtained by using of the moving plane method, in a nonlocal setting, on the whole $\mathbb{R}^N$ and by some comparison results. Moreover, in order to find the asymptotic behavior of solutions, we use a representation result that allows to transform the original problem into a different nonlocal problem in a weighted fractional space.

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arXiv2015

Global existence versus blow-up results for a fourth order parabolic PDE involving the Hessian

We consider a partial differential equation that arises in the coarse-grained description of epitaxial growth processes. This is a parabolic equation whose evolution is governed by the competition between the determinant of the Hessian matrix of the solution and the biharmonic operator. This model might present a gradient flow structure depending on the boundary conditions. We first extend previous results on the existence of stationary solutions to this model for Dirichlet boundary conditions. For the evolution problem we prove local existence of solutions for arbitrary data and global existence of solutions for small data. By exploiting the boundary conditions and the variational structure of the equation, according to the size of the data we prove finite time blow-up of the solution and/or convergence to a stationary solution for global solutions.

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arXiv2015

Existence results for a fourth order partial differential equation arising in condensed matter physics

We study a higher order parabolic partial differential equation that arises in the context of condensed matter physics. It is a fourth order semilinear equation whose nonlinearity is the determinant of the Hessian matrix of the solution. We consider this model in a bounded domain of the real plane and study its stationary solutions both when the geometry of this domain is arbitrary and when it is the unit ball and the solution is radially symmetric. We also consider the initial-boundary value problem for the full parabolic equation. We summarize our results on existence of solutions in these cases and propose an open problem related to the existence of self-similar solutions.

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arXiv2013

Some fourth order nonlinear elliptic problems related to epitaxial growth

This paper deals with some mathematical models arising in the theory of epitaxial growth of crystal. We focalize the study on a stationary problem which presents some analytical difficulties. We study the existence of solutions. The central model in this work is given by the following fourth order elliptic equation, $$\begin{array}{rclll} Δ^2 u=\text{det} \left(D^2 u \right) &+&λf, \quad & x\in Ω\subset\mathbb{R}^2\\ \hbox{conditions on} &\quad& & \partial Ω. \end{array} $$ The framework to study the problem deeply depends on the boundary conditions.

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arXiv2013

On radial stationary solutions to a model of nonequilibrium growth

We present the formal geometric derivation of a nonequilibrium growth model that takes the form of a parabolic partial differential equation. Subsequently, we study its stationary radial solutions by means of variational techniques. Our results depend on the size of a parameter that plays the role of the strength of forcing. For small forcing we prove the existence and multiplicity of solutions to the elliptic problem. We discuss our results in the context of nonequilibrium statistical mechanics.

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arXiv2013

Existence and nonexistence results for a singular boundary value problem arising in the theory of epitaxial growth

The existence of stationary radial solutions to a partial differential equation arising in the theory of epitaxial growth is studied. Our results depend on the size of a parameter that plays the role of the velocity at which mass is introduced into the system. For small values of this parameter we prove existence of solutions to this boundary value problem. For large values of the same parameter we prove nonexistence of solutions. We also provide rigorous bounds for the values of this parameter which separate existence from nonexistence. The proofs come as a combination of several differential inequalities and the method of upper and lower functions.

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arXiv2013

A Widder's type Theorem for the heat equation with nonlocal diffusion

The main goal of this work is to prove that every non-negative {\it strong solution} $u(x,t)$ to the problem $$ u_t+(-Δ)^{α/2}u=0 \ \quad\mbox{for } (x,t)\in\mathbb{R}^{n}\times(0,T), \quad 0<α<2, $$ can be written as $$u(x,t)=\int_{\mathbb{R}^{n}}{P_{t}(x-y)u(y,0)\, dy},$$ where $$P_{t}(x)=\frac{1}{t^{n/α}}P\left(\frac{x}{t^{1/α}}\right), $$ and $$ P(x):=\int_{\mathbb{R}^{n}}{e^{ix\cdotξ-|ξ|^α}dξ}. $$ This result shows uniqueness in the setting of non-negative solutions and extends some classical results for the heat equation by D. V. Widder in \cite{W0} to the nonlocal diffusion framework.

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