arXiv subjects

Manuel del Pino

Publications and source records attributed to Manuel del Pino.

At least 55 records · Page 3Linked to original sources

arXiv2018

Interface dynamics in semilinear wave equations

We consider the wave equation $\varepsilon^2(-\partial_t^2 + Δ)u + f(u) = 0$ for $0<\varepsilon\ll 1$, where $f$ is the derivative of a balanced, double-well potential, the model case being $f(u) = u-u^3$. For equations of this form, we construct solutions that exhibit an interface of thickness $O(\varepsilon )$ that separates regions where the solution is $O(\varepsilon^k)$ close to $\pm 1$, and that is close to a timelike hypersurface of vanishing {\em Minkowskian} mean curvature. This provides a Minkowskian analog of the numerous results that connect the Euclidean Allen-Cahn equation and minimal surfaces or the parabolic Allen-Cahn equation and motion by mean curvature. Compared to earlier results of the same character, we develop a new constructive approach that applies to a larger class of nonlinearities and yields much more precise information about the solutions under consideration.

math.AP↗

arXiv2018

Gluing methods for vortex dynamics in Euler flows

A classical problem for the two-dimensional Euler flow for an incompressible fluid confined to a smooth domain. is that of finding regular solutions with highly concentrated vorticities around $N$ moving {\em vortices}. The formal dynamic law for such objects was first derived in the 19th century by Kirkhoff and Routh. In this paper we devise a {\em gluing approach} for the construction of smooth $N$-vortex solutions. We capture in high precision the core of each vortex as a scaled finite mass solution of Liouville's equation plus small, more regular terms. Gluing methods have been a powerful tool in geometric constructions by {\em desingularization}. We succeed in applying those ideas in this highly challenging setting.

math.AP↗

arXiv2017

Ancient multiple-layer solutions to the Allen-Cahn equation

We consider the parabolic one-dimensional Allen-Cahn equation $$u_t= u_{xx}+ u(1-u^2)\quad (x,t)\in \mathbb{R}\times (-\infty, 0].$$ The steady state $w(x) =\tanh (x/\sqrt{2})$, connects, as a "transition layer" the stable phases $-1$ and $+1$. We construct a solution $u$ with any given number $k$ of transition layers between $-1$ and $+1$. At main order they consist of $k$ time-traveling copies of $w$ with interfaces diverging one to each other as $t\to -\infty$. More precisely, we find $$ u(x,t) \approx \sum_{j=1}^k (-1)^{j-1}w(x-ξ_j(t)) + \frac 12 ((-1)^{k-1}- 1)\quad \hbox{as} t\to -\infty, $$ where the functions $ξ_j(t)$ satisfy a first order Toda-type system. They are given by $$ξ_j(t)=\frac{1}{\sqrt{2}}\left(j-\frac{k+1}{2}\right)\log(-t)+γ_{jk},\quad j=1,...,k,$$ for certain explicit constants $γ_{jk}.$

math.AP↗

arXiv2017

Ancient shrinking spherical interfaces in the Allen-Cahn flow

We consider the parabolic Allen-Cahn equation in $\mathbb{R}^n$, $n\ge 2$, $$u_t= Δu + (1-u^2)u \quad \hbox{ in } \mathbb{R}^n \times (-\infty, 0].$$ We construct an ancient radially symmetric solution $u(x,t)$ with any given number $k$ of transition layers between $-1$ and $+1$. At main order they consist of $k$ time-traveling copies of $w$ with spherical interfaces distant $O(\log |t| )$ one to each other as $t\to -\infty$. These interfaces are resemble at main order copies of the {\em shrinking sphere} ancient solution to mean the flow by mean curvature of surfaces: $|x| = \sqrt{- 2(n-1)t}$. More precisely, if $w(s)$ denotes the heteroclinic 1-dimensional solution of $w'' + (1-w^2)w=0$ $w(\pm \infty)= \pm 1$ given by $w(s) = \tanh \left(\frac s{\sqrt{2}} \right) $ we have $$ u(x,t) \approx \sum_{j=1}^k (-1)^{j-1}w(|x|-ρ_j(t)) - \frac 12 (1+ (-1)^{k}) \quad \hbox{ as } t\to -\infty $$ where $$ρ_j(t)=\sqrt{-2(n-1)t}+\frac{1}{\sqrt{2}}\left(j-\frac{k+1}{2}\right)\log\left(\frac {|t|}{\log |t| }\right)+ O(1),\quad j=1,\ldots ,k.$$

math.AP↗

arXiv2016

Green's function and infinite-time bubbling in the critical nonlinear heat equation

Let $Ω$ be a smooth bounded domain in $\R^n$, $n\ge 5$. We consider the semilinear heat equation at the critical Sobolev exponent $$ u_t = Δu + u^{\frac{n+2}{n-2}} \inn Ω\times (0,\infty), \quad u =0 \onn \ppΩ\times (0,\infty). $$ Let $G(x,y)$ be the Dirichlet Green's function of $-Δ$ in $Ω$ and $H(x,y)$ its regular part. Let $q_j\in Ω$, $j=1,\ldots,k$, be points such that the matrix $$ \left [ \begin{matrix} H(q_1, q_1) & -G(q_1,q_2) &\cdots & -G(q_1, q_k) -G(q_1,q_2) & H(q_2,q_2) & -G(q_2,q_3) \cdots & -G(q_3,q_k) \vdots & & \ddots& \vdots -G(q_1,q_k) &\cdots& -G(q_{k-1}, q_k) & H(q_k,q_k) \end{matrix} \right ] $$ is positive definite. For any $k\ge 1$ such points indeed exist. We prove the existence of a positive smooth solution $u(x,t)$ which blows-up by bubbling in infinite time near those points. More precisely, for large time $t$, $u$ takes the approximate form $$ u(x,t) \approx \sum_{j=1}^k α_n \left ( \frac { μ_j(t)} { μ_j(t)^2 + |x-ξ_j(t)|^2 } \right )^{\frac {n-2}2} . $$ Here $ξ_j(t) \to q_j$ and $0<μ_j(t) \to 0$, as $t \to \infty$. We find that $μ_j(t) \sim t^{-\frac 1{n-4}} $ as $t\to +\infty$, when $n\geq 5$.

math.AP↗

arXiv2016

Large mass boundary condensation patterns in the stationary Keller-Segel system

We consider the boundary value problem $-Δu + u =λe^u$ in $Ω$ with Neumann boundary condition, where $Ω$ is a bounded smooth domain in $\mathbb R^2$, $λ>0.$ This problem is equivalent to the stationary Keller-Segel system from chemotaxis. We establish the existence of a solution $u_λ$ which exhibits a sharp boundary layer along the entire boundary $\partialΩ$ as $λ\to 0$. These solutions have large mass in the sense that $ \int_Ωλe^{u_λ} \sim |\logλ|.$

math.AP↗

arXiv2016

New type I ancient compact solutions of the Yamabe flow

We construct new ancient compact solutions to the Yamabe flow. Our solutions are rotationally symmetric and converge, as $t \to -\infty$, to two self-similar complete non-compact solutions to the Yamabe flow moving in opposite directions. They are type I ancient solutions.

math.DG↗

arXiv2015

Interior bubbling solutions for the critical Lin-Ni-Takagi problem in dimension 3

We consider the problem of finding positive solutions of the problem $Δu - λu +u^5 = 0$ in a bounded, smooth domain $Ω$ in $\mathbb{R}^3$, under zero Neumann boundary conditions. Here $λ$ is a positive number. We analyze the role of Green's function of $-Δ+λ$ in the presence of solutions exhibiting single bubbling behavior at one point of the domain when $λ$ is regarded as a parameter. As a special case of our results, we find and characterize a positive value $λ_*$ such that if $λ-λ^*>0$ is sufficiently small, then this problem is solvable by a solution $u_λ$ which blows-up by bubbling at a certain interior point of $Ω$ as $λ\downarrow λ_*$.

math.AP↗

arXiv2015

Nonlocal Delaunay surfaces

We construct codimension 1 surfaces of any dimension that minimize a periodic nonlocal perimeter functional among surfaces that are periodic, cylindrically symmetric and decreasing. These surfaces may be seen as a nonlocal analogue of the classical Delaunay surfaces (onduloids). For small volume, most of their mass tends to be concentrated in a periodic array and the surfaces are close to a periodic array of balls (in fact, we give explicit quantitative bounds on these facts).

math.AP↗

arXiv2015

Type I ancient compact solutions of the Yamabe flow

math.DG↗

arXiv2015

Catenoidal layers for the Allen-Cahn equation in bounded domains

In this paper we present a new family of solutions to the singularly perturbed Allen-Cahn equation $α^2 Δu + u(1-u^2)=0, \quad \hbox{in }Ω\subset \R^N $ where $N=3$, $Ω$ is a smooth bounded domain and $\A>0$ is a small parameter. We provide asymptotic behavior which shows that, as $α\to 0$, the level sets of the solutions collapse onto a bounded portion of a complete embedded minimal surface with finite total curvature that intersects orthogonally $\partial Ω$ of the domain and that is non-degenerate respect to $Ω$. We provide explicit examples of surfaces to which our result applies.

math.AP↗

arXiv2015

Finite topology self-translating surfaces for the mean curvature flow in $\mathbb R^3$

Finite topology self translating surfaces to mean curvature flow of surfaces constitute a key element for the analysis of Type II singularities from a compact surface, since they arise in a limit after suitable blow-up scalings around the singularity. We find in $\mathbb R^3$ a surface $M$ orientable, embedded and complete with finite topology (and large genus) with three ends asymptotically paraboloidal, such that the moving surface $Σ(t) = M + te_z$ evolves by mean curvature flow. This amounts to the equation $H_M = ν\cdot e_z$ where $H_M$ denotes mean curvature, $ν$ is a choice of unit normal to $M$, and $e_z$ is a unit vector along the $z$-axis. The surface $M$ is in correspondence with the classical 3-end Costa-Hoffmann-Meeks minimal surface with large genus, which has two asymptotically catenoidal ends and one planar end, and a long array of small tunnels in the intersection region resembling a periodic Scherk surface. This example is the first non-trivial one of its kind, and it suggests a strong connection between this problem and the theory of embedded, complete minimal surfaces with finite total curvature.

math.AP↗

arXiv2014

Non-topological condensates for the self-dual Chern-Simons-Higgs model

For the abelian self-dual Chern-Simons-Higgs model we address existence issues of periodic vortex configurations -- the so-called condensates-- of non-topological type as $k \to 0$, where $k>0$ is the Chern-Simons parameter. We provide a positive answer to the long-standing problem on the existence of non-topological condensates with magnetic field concentrated at some of the vortex points (as a sum of Dirac measures) as $k \to 0$, a question which is of definite physical interest.

math.AP↗

arXiv2014

Large Conformal metrics with prescribed sign-changing Gauss curvature

Let $(M,g)$ be a two dimensional compact Riemannian manifold of genus $g(M)>1$. Let $f$ be a smooth function on $M$ such that $$f \ge 0, \quad f\not\equiv 0, \quad \min_M f = 0. $$ Let $p_1,\ldots,p_n$ be any set of points at which $f(p_i)=0$ and $D^2f(p_i)$ is non-singular. We prove that for all sufficiently small $λ>0$ there exists a family of "bubbling" conformal metrics $g_λ=e^{u_λ}g$ such that their Gauss curvature is given by the sign-changing function $K_{g_λ}=-f+λ^2$. Moreover, the family $u_λ$ satisfies $$u_λ(p_j) = -4\logλ-2\log \left (\frac 1{\sqrt{2}} \log \frac 1λ\right ) +O(1)$$ and $$λ^2e^{u_λ}\rightharpoonup8π\sum_{i=1}^{n}δ_{p_i},\quad \mbox{as }λ\to 0,$$ where $δ_{p}$ designates Dirac mass at the point $p$.

math.AP↗

arXiv2014

Concentration phenomena for the nonlocal Schrödinger equation with Dirichlet datum

For a smooth, bounded domain $Ω$, $s\in(0,1)$, $p\in \left(1,\frac{n+2s}{n-2s}\right)$ we consider the nonlocal equation $$ ε^{2s} (-Δ)^s u+u=u^p \quad {\mbox{in}}Ω$$ with zero Dirichlet datum and a small parameter $ε>0$. We construct a family of solutions that concentrate as $ε\to 0$ at an interior point of the domain in the form of a scaling of the ground state in entire space. Unlike the classical case $s=1$, the leading order of the associated reduced energy functional in a variational reduction procedure is of polynomial instead of exponential order on the distance from the boundary, due to the nonlocal effect. Delicate analysis is needed to overcome the lack of localization, in particular establishing the rather unexpected asymptotics for the Green function of $ ε^{2s} (-Δ)^s +1$ in the expanding domain $ε^{-1}Ω$ with zero exterior datum.

math.AP↗

arXiv2014

Nonlocal $s$-minimal surfaces and Lawson cones

The nonlocal $s$-fractional minimal surface equation for $Σ= \partial E$ where $E$ is an open set in $R^N$ is given by $$ H_Σ^ s (p) := \int_{R^N} \frac {χ_E(x) - χ_{E^c}(x)} {|x-p|^{N+s}}\, dx \ =\ 0 \quad \text{for all } p\in Σ. $$ Here $0<s<1$, $χ$ designates characteristic function, and the integral is understood in the principal value sense. The classical notion of minimal surface is recovered by letting $s\to 1$. In this paper we exhibit the first concrete examples (beyond the plane) of nonlocal $s-$minimal surfaces. When $s$ is close to $1$, we first construct a connected embedded $s$-minimal surface of revolution in $R^3$, the {\bf nonlocal catenoid}, an analog of the standard catenoid $|x_3| = \log (r + \sqrt{r^2 -1})$. Rather than eventual logarithmic growth, this surface becomes asymptotic to the cone $|x_3|= r\sqrt{1-s}$. We also find a two-sheet embedded $s$-minimal surface asymptotic to the same cone, an analog to the simple union of two parallel planes. On the other hand, for any $0<s<1$, $n,m\ge 1$, $s-$minimal Lawson cones $|v|=α|u|$, $(u,v)\in R^n\times R^m$, are found to exist. In sharp contrast with the classical case, we prove their stability for small $s$ and $n+m=7$, which suggests that unlike the classical theory (or the case $s$ close to 1), the regularity of $s$-area minimizing surfaces may not hold true in dimension $7$.

math.AP↗

arXiv2013

Serrin's Overdetermined Problem and Constant Mean Curvature Surfaces

For all $N \geq 9$, we find smooth entire epigraphs in $\R^N$, namely smooth domains of the form $Ω: = \{x\in \R^N\ / \ x_N > F (x_1,\ldots, x_{N-1})\}$, which are not half-spaces and in which a problem of the form $Δu + f(u) = 0 $ in $Ω$ has a positive, bounded solution with 0 Dirichlet boundary data and constant Neumann boundary data on $\partial Ω$. This answers negatively for large dimensions a question by Berestycki, Caffarelli and Nirenberg \cite{bcn2}. In 1971, Serrin \cite{serrin} proved that a bounded domain where such an overdetermined problem is solvable must be a ball, in analogy to a famous result by Alexandrov that states that an embedded compact surface with constant mean curvature (CMC) in Euclidean space must be a sphere. In lower dimensions we succeed in providing examples for domains whose boundary is close to large dilations of a given CMC surface where Serrin's overdetermined problem is solvable.

math.AP↗

arXiv2013

Infinitely many positive solutions of nonlinear Schrödinger equations with non-symmetric potentials

We consider the standing-wave problem for a nonlinear Schrödinger equation, corresponding to the semilinear elliptic problem \begin{equation*} -Δu+V(x)u=|u|^{p-1}u,\ u\in H^1(\mathbb{R}^2), \end{equation*} where $V(x)$ is a uniformly positive potential and $p>1$. Assuming that \begin{equation*} V(x)=V_\infty+\frac{a}{|x|^m}+O\Big(\frac{1}{|x|^{m+σ}}\Big),\ \text{as}\ |x|\rightarrow+\infty, %\tag{$V2$} \end{equation*} for instance if $p>2$, $m>2$ and $σ>1$ we prove the existence of infinitely many positive solutions. If $V(x)$ is radially symmetric, this result was proved in \cite{WY-10}. The proof without symmetries is much more difficult, and for that we develop a new {\em intermediate Lyapunov-Schmidt reduction method}, which is a compromise between the finite and infinite dimensional versions of it.

math.AP↗