arXiv subjects
Publications and source records attributed to Francesca Gladiali.
In this paper, we construct new sign-changing solutions for the Hénon problem \begin{equation*} \begin{cases} -Δu= |x|^α |u|^{p-1}u,\,\,\,\text{in}\,\,\, Ω, \\[1mm] u=0,\,\,\,\,\,\,\text{on}\,\,\, \partialΩ, \end{cases} \end{equation*} where $Ω\subseteq \mathbb{R}^2$ is a bounded smooth domain containing 0, $α\in\mathbb{R}$ is a positive parameter and $p$ approaches $+\infty$.
We study optimal control problems for a stationary reaction--diffusion model describing the spatial distribution of a tumor cell population with Gompertz growth. The control $m(x)$ represents a treatment term acting as a density-dependent removal rate and it is subject to $L^{1}-L^{\infty}$ constraints. When the intrinsic growth rate is constant, the uniform distribution of the treatment is shown to be the unique minimizer. For the maximization problem, we prove that every optimal control is of bang-bang type. In addition, we show that in the one dimensional case and for sufficiently large diffusion rates, the positivity set of optimal controls is an interval sticking to one of the extrema of the domain. Finally, numerical simulations complement the theoretical analysis and explore regimes that are not fully covered by the results proved in the paper. The computations confirm the bang-bang structure of maximizers, and illustrate how the shape of optimal controls and the associated states are affected by spatial heterogeneity in the growth rate, localized admissible treatment regions, and the diffusion coefficient. Moreover, they reveal a monotone dependence of the optimized total population on the diffusion coefficient: this is a new phenomenon with respect to the logistic setting.
In this paper, we study the number of critical points of the Kirchhoff-Routh function \begin{equation*} \mathcal{KR}_D(x,y)=Λ_1^2\mathcal{R}_D(x)+Λ_2^2\mathcal{R}_D(y)-2Λ_1Λ_2G_D(x,y), \end{equation*} where $D$ is a bounded domain in $\mathbb{R}^2$, $x,y\in D$, $Λ_1,Λ_2>0$, $\mathcal{R}_D$ is the Robin function, and $G_D$ is the Green function of the operator $-Δ$ with $0$ Dirichlet boundary condition on $D$. This function arises from concentration phenomena in nonlinear elliptic problems and from the de-singularization problem for the steady Euler equation. For domains with a small hole, we establish not only the exact number and the location of the critical points of $\mathcal{KR}_D$, but also their nondegeneracy. We show that the location of the hole plays a crucial role. Finally in the context of elliptic problems, we establish the existence of multiple two-peak solutions.
We prove uniqueness and non-degeneracy of the critical point of positive, semi-stable solutions of $-Δu=f(u)$ with Dirichlet boundary conditions for a class of star-shaped domains of the sphere and of the hyperbolic plane satisfying a geometric condition. In the spherical case, this condition is weaker than convexity, while in the hyperbolic case it is weaker than horoconvexity. Finally, we construct examples showing that this geometric condition is indeed optimal.
Consider a complete $d$-dimensional Riemannian manifold $(\mathcal M,g)$, a point $p\in\mathcal M$ and a nonlinearity $f(q,u)$ with $f(p,0)>0$. We prove that for any odd integer $N\ge3$, there exists a sequence of smooth domains $Ω_k\subset\mathcal M$ containing $p$ and corresponding positive solutions $u_k:Ω_k\to\R^+$ to the Dirichlet boundary problem
In this paper we are concerned with the number of critical points of solutions of nonlinear elliptic equations. We will deal with the case of non-convex, contractile and non-contractile planar domains. We will prove results on the estimate of their number as well as their index. In some cases we will provide the exact calculation. The toy problem concerns the multi-peak solutions of the Gel'fand problem, namely $$\begin{cases} -Δu=λe^{u}&\mbox{ in }Ω u=0 & \mbox{ on }\partialΩ, \end{cases} $$ where $Ω\subset\mathbb{R}^2$ is a bounded smooth domain and $λ>0$ is a small parameter.
Let $Ω\subset\mathbb{R}^N$ be a smooth bounded domain with $N\ge2$ and $Ω_ε=Ω\backslash B(P,ε)$ where $B(P,ε)$ is the ball centered at $P\inΩ$ and radius $ε$. In this paper, we establish the number, location and non-degeneracy of critical points of the Robin function in $Ω_ε$ for $ε$ small enough. We will show that the location of $P$ plays a crucial role on the existence and multiplicity of the critical points. The proof of our result is a consequence of delicate estimates on the Green function near to $\partial B(P,ε)$. Some applications to compute the exact number of solutions of related well-studied nonlinear elliptic problems will be showed.
In this manuscript we consider semilinear PDEs, with a convex nonlinearity, in a sector-like domain. Using cylindrical coordinates $(r, θ, z)$, we investigate the shape of solutions whose derivative in $θ$ vanishes at the boundary. We prove that any solution with Morse index less than two must be either independent of $θ$ or strictly monotone with respect to $θ$. In the special case of a planar domain, the result holds in a circular sector as well as in an annular, and it can also be extended to a rectangular domain. The corresponding problem in higher dimensions is also considered, as well as an extension to unbounded domains. The proof is based on a rotating-plane argument: a convenient manifold is introduced in order to avoid overlapping the domain with its reflected image in the case when its opening is larger than $π$.
In this paper we construct families of bounded domains $Ω_\varepsilon$ and solutions $u_\varepsilon$ of \[\begin{cases} -Δu_\varepsilon=1&\text{ in }\ Ω_\varepsilon\\ u_\varepsilon=0&\text{ on }\ \partialΩ_\varepsilon \end{cases}\] such that, for any integer $k\ge2$, $u_\varepsilon$ admits at least $k$ maxima points for small enough $\varepsilon$. The domain $Ω_\varepsilon$ is "not far" to be convex in the sense that it is starshaped, the curvature of $\partialΩ_\varepsilon$ vanishes at exactly $two$ points and the minimum of the curvature of $\partialΩ_\varepsilon$ goes to $0$ as $\varepsilon\to0$.
In this paper we consider nodal radial solutions of the problem $$ \begin{cases} -Δu=|u|^{2^*-2}u+λu&\text{ in }B,\\ u=0&\text{ on }\partial B \end{cases} $$ where $2^*=\frac{2N}{N-2}$ with $3\le N\le6$ and $B$ is the unit ball of $\R^N$. We compute the asymptotics of the solution $u$ as well as $||u||_\infty$, its first zero and other relevant quantities as $ł$ goes to a critical value $\barł$. Also the sign of $ł-\barł$ is established in all cases. This completes an analogous analysis for $N\ge7$ given in [EGPV].
In this paper, we prove existence of multiple non-radial solutions to the Hardy-Sobolev equation $$\begin{cases} -Δu-\displaystyle\frac γ{|x|^2}u=\displaystyle\frac{1}{|x|^s}|u|^{p_s-2}u & \text{ in } \mathbb{R}^N\setminus\{0\},\\ u\geq 0, & \end{cases}$$ where $N\geq 3$, $s\in[0,2)$, $p_s=\frac{2(N-s)}{N-2}$ and $γ\in (-\infty,\frac{(N-2)^2} 4)$. We extend results of E.N. Dancer, F. Gladiali, M. Grossi, Proc. Roy. Soc. Edinburgh Sect. A 147 (2017) where only the case $s=0$ is considered. Moreover, thanks to monotonicity properties of the solutions, we separate two branches of non-radial solutions.
We consider the Dirichlet problem $-Δu=λf(u)$ with $λ<0$ and $f$ non-negative and non-decreasing. We show existence and uniqueness of solutions $u_λ$ for any $λ$ and discuss their asymptotic behavior as $λ\to-\infty$. In the expansion of $u_λ$ large solutions naturally appear.
In this paper we consider some nodal solutions of the Hénon problem in the unit disc with Dirichlet boundary conditions and we show that they are quasiradial, that is to say they are nonradial, they have two nodal regions and their nodal line does not touch the boundary of the disc.
We investigate nodal radial solutions to semilinear problems of type \[\begin{cases}-Δu = f(|x|,u) \qquad & \text{ in } Ω, \newline u= 0 & \text{ on } \partial Ω, \end{cases} \] where $Ω$ is a bounded radially symmetric domain of $\mathbb R^N$ ($N\ge 2$) and $f$ is a real function. We characterize both the Morse index and the degeneracy in terms of a singular one dimensional eigenvalue problem, which is studied in full detail. The presented approach also describes the symmetries of the eigenfunctions. This characterization enables to give a lower bound for the Morse index in a forthcoming work.
By using a characterization of the Morse index and the degeneracy in terms of a singular one dimensional eigenvalue problem given in a previous paper, we give a lower bound for the Morse index of radial solutions to Hénon type problems \[ \left\{\begin{array}{ll} -Δu = |x|^αf(u) \qquad & \text{ in } Ω, u= 0 & \text{ on } \partial Ω, \end{array} \right. \] where $Ω$ is a bounded radially symmetric domain of $\mathbb R^N$ ($N\ge 2$), $α>0$ and $f$ is a real function. From this estimate we get that the Morse index of nodal radial solutions to this problem goes to $\infty$ as $α\to \infty$. Concerning the real Hénon problem, $f(u)= |u|^{p-1}u$, we prove radial nondegeneracy, we show that the radial Morse index is equal to the number of nodal zones and we get that a least energy nodal solution is not radial.
In this paper we consider the Hénon problem in the unit disc with Dirichlet boundary conditions. We study the asymptotic profile of least energy and nodal least energy radial solutions and then deduce the exact computation of their Morse index for large values of the exponent p. As a consequence of this computation a multiplicity result for positive and nodal solutions is obtained.
This paper deals with solutions of semilinear elliptic equations of the type \[ \left\{\begin{array}{ll} -Δu = f(|x|, u) \qquad & \text{ in } Ω, \\ u= 0 & \text{ on } \partial Ω, \end{array} \right. \] where $Ω$ is a radially symmetric domain of the plane that can be bounded or unbounded. We consider solutions $u$ that are invariant by rotations of a certain angle $θ$ and which have a bound on their Morse index in spaces of functions invariant by these rotations. We can prove that or $u$ is radial, or, else, there exists a direction $e\in \mathcal S$ such that $u$ is symmetric with respect to $e$ and it is strictly monotone in the angular variable in a sector of angle $\fracθ2$. The result applies to least-energy and nodal least-energy solutions in spaces of functions invariant by rotations and produces multiplicity results.
We compute the Morse index of nodal radial solutions to the Hénon problem \[\left\{\begin{array}{ll} -Δu = |x|^α|u|^{p-1} u \qquad & \text{ in } B, \newline u= 0 & \text{ on } \partial B, \end{array} \right. \] where $B$ stands for the unit ball in ${\mathbb R}^N$ in dimension $N\ge 3$, $α>0$ and $p$ is near at the threshold exponent for existence of solutions $p_α=\frac{N+2+2α}{N-2}$, obtaining that \begin{align*} m(u_p) & = m \sum\limits_{j=0}^{1+\left[α/{2}\right]} N_j \quad & \mbox{ if $α$ is not an even integer, or} \newline m(u_p)& = m\sum\limits_{j=0}^{ α/2} N_j + (m-1) N_{1+α/ 2} & \mbox{ if $α$ is an even number.} \end{align*} Here $N_j$ denotes the multiplicity of the spherical harmonics of order $j$. The computation builds on a characterization of the Morse index by means of a one dimensional singular eigenvalue problem, and is carried out by a detailed picture of the asymptotic behavior of both the solution and the singular eigenvalues and eigenfunctions. In particular it is shown that nodal radial solutions have multiple blow-up at the origin, where each node converges (up to a suitable rescaling) to the bubble shaped solution of a limit problem. As side outcome we see that solutions are nondegenerate for $p$ near at $p_α$, and we give an existence result in perturbed balls.