arXiv subjects

Monica Musso

Publications and source records attributed to Monica Musso.

At least 55 records · Page 3Linked to original sources

arXiv2020

Type II Finite time blow-up for the three dimensional energy critical heat equation

We consider the following Cauchy problem for three dimensional energy critical heat equation \begin{equation*} \begin{cases} u_t=Δu+u^{5},~&\mbox{ in } \ {\mathbb R}^3 \times (0,T),\\ u(x,0)=u_0(x),~&\mbox{ in } \ {\mathbb R}^3. \end{cases} \end{equation*} We construct type II finite time blow-up solution $u(x,t)$ with the blow-up rates $ \| u\|_{L^\infty} \sim (T-t)^{-k}$, where $ k=1,2,... $. This gives a rigorous proof of the formal computations by Filippas, Herrero and Velazquez \cite{fhv}. This is the first instance of type II finite time blow-up for three dimensional energy critical heat equation.

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arXiv2020

Geometry driven Type II higher dimensional blow-up for the critical heat equation

We consider the problem v_t & = Δv+ |v|^{p-1}v \quad\hbox{in }\ Ω\times (0, T), v & =0 \quad\hbox{on } \partial Ω\times (0, T ) , v& >0 \quad\hbox{in }\ Ω\times (0, T) . In a domain $Ω\subset \mathbb R^d$, $d\ge 7$ enjoying special symmetries, we find the first example of a solution with type II blow-up for a power $p$ less than the Joseph-Lundgren exponent $$p_{JL}(d)=\infty, & \text{if $3\le d\le 10$}, 1+{4\over d-4-2\,\sqrt{d-1}}, & \text{if $d\ge11$}. $$ No type II radial blow-up is present for $p< p_{JL}(d)$. We take $p=\frac{d+1}{d-3}$, the Sobolev critical exponent in one dimension less. The solution blows up on circle contained in a negatively curved part of the boundary in the form of a sharply scaled Aubin-Talenti bubble, approaching its energy density a Dirac measure for the curve. This is a completely new phenomenon for a diffusion setting.

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arXiv2019

Compactness of scalar-flat conformal metrics on low-dimensional manifolds with constant mean curvature on boundary

We concern $C^2$-compactness of the solution set of the boundary Yamabe problem on smooth compact Riemannian manifolds with boundary provided that their dimensions are $4$, $5$ or $6$. By conducting a quantitative analysis of a linear equation associated with the problem, we prove that the trace-free second fundamental form must vanish at possible blow-up points of a sequence of blowing-up solutions. Applying this result and the positive mass theorem, we deduce the $C^2$-compactness for all $4$-manifolds (which may be non-umbilic). For the $5$-dimensional case, we also establish that a sum of the second-order derivatives of the trace-free second fundamental form is non-negative at possible blow-up points. We essentially use this fact to obtain the $C^2$-compactness for all $5$-manifolds. Finally, we show that the $C^2$-compactness on $6$-manifolds is true if the trace-free second fundamental form on the boundary never vanishes.

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arXiv2019

Existence and stability of infinite time bubble towers in the energy critical heat equation

We consider the energy critical heat equation in $\mathbb R^n$ for $n\ge 7$ $$\left\{ \begin{aligned} u_t & = Δu+ |u|^{\frac 4{n-2}}u \hbox{ in }\ \mathbb R^n \times (0, \infty), \\ u(\cdot,0) & = u_0 \ \hbox{ in }\ \mathbb R^n, \end{aligned}\right. $$ which corresponds to the $L^2$-gradient flow of the Sobolev-critical energy $$ J(u) = \int_{\mathbb R^n} e[u] , \quad e[u] := \frac 12 |\nabla u|^2 - \frac {n-2}{2n} |u|^{\frac {2n}{n-2} }. $$ Given any $k\ge 2$ we find an initial condition $u_0$ that leads to sign-changing solutions with {\em multiple blow-up at a single point} (tower of bubbles) as $t\to +\infty$. It has the form of a superposition with alternate signs of singularly scaled {\em Aubin-Talenti solitons}, $$ u(x,t) = \sum_{j=1}^k (-1)^{j-1} {μ_j^{-\frac {n-2}2}} U \left( \frac {x}{μ_j} \right)\, +\, o(1) \quad\hbox{as } t\to +\infty $$ where $U(y)$ is the standard soliton $ U(y) = % (n(n-2))^{\frac 1{n-2}} α_n\left ( \frac 1{1+|y|^2}\right)^{\frac{n-2}2}$ and $$μ_j(t) = β_j t^{- α_j}, \quad α_j = \frac 12 \Big ( \, \left( \frac{n-2}{n-6}\right)^{j-1} -1 \Big). $$ Letting $δ_0$ the Dirac mass, we have energy concentration of the form $$ e[ u(\cdot, t)]- e[U] \rightharpoonup (k-1) S_n\,δ_{0} \quad\hbox{as } t\to +\infty $$ where $S_n=J(U)$. The initial condition can be chosen radial and compactly supported. We establish the codimension $k+ n (k-1)$ stability of this phenomenon for perturbations of the initial condition that have space decay $u_0(x) =O( |x|^{-α})$, $α> \frac {n-2}2$, which yields finite energy of the solution.

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arXiv2018

Sign-changing blowing-up solutions for the critical nonlinear heat equation

Let $Ω$ be a smooth bounded domain in $\mathbb{R}^n$ and denote the regular part of the Green's function on $Ω$ with Dirichlet boundary condition as $H(x,y)$. Assume that $q \in Ω$ and $n\geq 5$. We prove that there exists an integer $k_0$ such that for any integer $k\geq k_0$ there exist initial data $u_0$ and smooth parameter functions $ξ(t)\to q$, $0<μ(t)\to 0$ as $t\to +\infty$ such that the solution $u_q$ of the critical nonlinear heat equation \begin{equation*} \begin{cases} u_t = Δu + |u|^{\frac{4}{n-2}}u\text{ in } Ω\times (0, \infty),\\ u = 0\text{ on } \partial Ω\times (0, \infty),\\ u(\cdot, 0) = u_0 \text{ in }Ω, \end{cases} \end{equation*} has the form \begin{equation*} u_q(x, t) \approx μ(t)^{-\frac{n-2}{2}}\left(Q_k\left(\frac{x-ξ(t)}{μ(t)}\right) - H(x, q)\right), \end{equation*} where the profile $Q_k$ is the non-radial sign-changing solution of the Yamabe equation \begin{equation*} ΔQ + |Q|^{\frac{4}{n-2}}Q = 0\text{ in }\mathbb{R}^n, \end{equation*} constructed in \cite{delpinomussofrankpistoiajde2011}. In dimension 5 and 6, we also prove the stability of $u_q(x, t)$.

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arXiv2018

Infinite time blow-up for the 3-dimensional energy critical heat equation

We construct globally defined in time, unbounded positive solutions to the energy-critical heat equation in dimension three $$ u_t = Δu + u^5 , \quad {\mbox {in}} \quad \R^3 \times (0,\infty), \ \ u(x, 0)= u_0 (x)\inn \R^3. $$ For each $γ>1$ we find initial data (not necessarily radially symmetric) with $\lim\limits_{r \to \infty} |x|^γu_0 (x) >0$ such that as $t \to \infty$ $$ \| u(\cdot ,t ) \|_\infty \sim t^{γ-1 \over 2} , \quad {\mbox {if}} \quad 1<γ<2, \quad \| u(\cdot ,t ) \|_\infty \sim \sqrt{t}, \quad {\mbox {if}} \quad γ>2, \quad $$ and $$ \| u(\cdot , t)\|_\infty \sim \sqrt{t}\, (\ln t )^{-1} , \quad {\mbox {if}} \quad γ= 2. $$ Furthermore we show that this infinite time blow-up is co-dimensional one stable. The existence of such solutions was conjectured by Fila and King.

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arXiv2018

Embedded tori with prescribed mean curvature

We construct a sequence of compact, oriented, embedded, two-dimensional surfaces of genus one into Euclidean 3-space with prescribed, almost constant, mean curvature of the form $H(X)=1+{A}{|X|^{-γ}}$ for $|X|$ large, when $A<0$ and $γ\in(0,2)$. Such surfaces are close to sections of unduloids with small necksize, folded along circumferences centered at the origin and with larger and larger radii. The construction involves a deep study of the corresponding Jacobi operators, an application of the Lyapunov-Schmidt reduction method and some variational argument.

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arXiv2018

Type II blow-up in the 5-dimensional energy critical heat equation

We consider the Cauchy problem for the energy critical heat equation $$ u_t = Δu + |u|^{\frac 4{n-2}}u {{\quad\hbox{in } }} \ {\mathbb R}^n \times (0, T), \quad u(\cdot,0) =u_0 {{\quad\hbox{in } }} {\mathbb R}^n $$ in dimension $n=5$. More precisely we find that for given points $q_1, q_2,\ldots, q_k$ and any sufficiently small $T>0$ there is an initial condition $u_0$ such that the solution $u(x,t)$ of the problem blows-up at exactly those $k$ points with rates type II, namely with absolute size $ \sim (T-t)^{-α} $ for $α> \frac 34 $. The blow-up profile around each point is of bubbling type, in the form of sharply scaled Aubin-Talenti bubbles.

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arXiv2018

A compactness theorem of the fractional Yamabe problem, Part I: The non-umbilic conformal infinity

Assume that $(X, g^+)$ is an asymptotically hyperbolic manifold, $(M, [\bar{h}])$ is its conformal infinity, $ρ$ is the geodesic boundary defining function associated to $\bar{h}$ and $\bar{g} = ρ^2 g^+$. For any $γ\in (0,1)$, we prove that the solution set of the $γ$-Yamabe problem on $M$ is compact in $C^2(M)$ provided that convergence of the scalar curvature $R[g^+]$ of $(X, g^+)$ to $-n(n+1)$ is sufficiently fast as $ρ$ tends to 0 and the second fundamental form on $M$ never vanishes. Since most of the arguments in blow-up analysis performed here is irrelevant to the geometric assumption imposed on $X$, our proof also provides a general scheme toward other possible compactness theorems for the fractional Yamabe problem.

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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.

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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.

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arXiv2018

Desingularization of Clifford Torus and Nonradial Solutions to Yamabe Problem with Maximal Rank

Through desingularization of Clifford torus, we prove the existence of a sequence of nondegenerate (in the sense of Duyckaerts-Kenig-Merle nodal nonradial solutions to the critical Yamabe problem $$-Δu=\frac{n(n-2)}{4}|u|^{\frac{4}{n-2}}u,\qquad u\in {\mathcal{D}}^{1,2}(\mathcal{R}^n). $$ The case $n=4$ is the first example in the literature of a solution with {\em maximal rank} ${\mathcal N}=2n+1+\frac{n(n-1)}{2}$.

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arXiv2017

Concentration at submanifolds for an elliptic Dirichlet problem near high critical exponents

Let $Ω$ be a open bounded domain in $\mathbb{R}^n $ with smooth boundary $\partialΩ$. We consider the equation $ Δu + u^{\frac{n-k+2}{n-k-2}-\varepsilon} =0\,\hbox{ in }\,Ω$, under zero Dirichlet boundary condition, where $\varepsilon$ is a small positive parameter. We assume that there is a $k$-dimensional closed, embedded minimal submanifold $K$ of $\partialΩ$, which is non-degenerate, and along which a certain weighted average of sectional curvatures of $\partialΩ$ is negative. Under these assumptions, we prove existence of a sequence $\varepsilon=\varepsilon_j$ and a solution $u_{\varepsilon}$ which concentrate along $K$, as $\varepsilon \to 0^+$, in the sense that $$ |\nabla u_{\varepsilon} |^2\,\rightharpoonup \, S_{n-k}^{\frac{n-k}{2}} \,δ_K \quad \mbox{as} \ \ \varepsilon \to 0 $$ where $δ_K $ stands for the Dirac measure supported on $K$ and $S_{n-k}$ is an explicit positive constant. This result generalizes the one obtained by del Pino-Musso-Pacard, where the case $k=1$ is considered.

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arXiv2017

High energy sign-changing solutions for Coron's problem

We study the existence of sign changing solutions to the following problem $$ (P) \quad \quad \quad \left\{ \begin{array}{ll} Δu+|u|^{p-1}u=0 \quad & {\rm in} \quad Ω_ε; u=0 \quad & {\rm on} \quad\partial Ω_ε, \end{array} \right. $$ where $p=\frac{n+2}{n-2}$ is the critical Sobolev exponent and $Ω_ε$ is a bounded smooth domain in ${\mathcal R}^n$, $n\geq 3$, with the form $Ω_ε=Ω\backslash B(0,ε)$ with $Ω$ a smooth bounded domain containing the origin $0$ and $B(0,ε)$ the ball centered at the origin with radius $ε>0$. We construct a new type of sign-changing solutions with high energy to problem $(P)$, when the parameter $ε$ is small enough.

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arXiv2017

Bubbling solutions for Moser-Trudinger type equations on compact Riemann surfaces

We study an elliptic equation related to the Moser-Trudinger inequality on a compact Riemann surface $(S,g)$, $$ Δ_g u+λ\Biggl(ue^{u^2}-{1\over |S|} \int_S ue^{u^2} dv_g\Biggl)=0,\quad\text{in $S$},\qquad \int_S u\,dv_g=0, $$ where $λ>0$ is a small parameter, $|S|$ is the area of $S$, $Δ_g$ is the Laplace-Beltrami operator and $dv_g$ is the area element. Given any integer $k\geq 1$, under general conditions on $S$ we find a bubbling solution $u_λ$ which blows up at exactly $k$ points in $S$, as $λ\to0$. When $S$ is a flat two-torus in rectangular form, we find that either seven or nine families of such solutions do exist for $k=2$. In particular, in any square flat two-torus actually nine families of bubbling solutions with two bubbling points do exist. If $S$ is a Riemann surface with non-constant Robin's function then at least two bubbling solutions with $k=1$ exists.

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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 $n\geq 5$.

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arXiv2016

New blow-up phenomena for SU(n+1) Toda system

We consider the $SU(n+1)$ Toda system $$(S_λ) \quad \left\{ \begin{aligned} & Δu_1 + 2λe^{u_1} - λe^{u_2}- \dots - λe^{u_k} = 0\quad \hbox{in}\ Ω,\\ & Δu_2 - λe^{u_1} + 2λe^{u_2} - \dots - λe^{u_k}=0\quad \hbox{in}\ Ω,\\ &\vdots \hskip3truecm \ddots \hskip2truecm \vdots\\ & Δu_k -λe^{u_1}-λe^{u_2}- \dots+2λe^{u_k}=0\quad \hbox{in}\ Ω, &u_1 = u_2 = \dots = u_k =0 \quad \hbox{on}\ \partialΩ.\\ \end{aligned}\right. $$ If $0\inΩ$ and $Ω$ is symmetric with respect to the origin, we construct a family of solutions $({u_1}_λ,\dots,{u_k}_λ)$ to $(S_λ)$ such that the $i-$th component ${u_i}_λ$ blows-up at the origin with a mass $2^{i+1}π$ as $λ$ goes to zero.

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arXiv2016

Existence theorems of the fractional Yamabe problem

Let $X$ be an asymptotically hyperbolic manifold and $M$ its conformal infinity. This paper is devoted to deduce several existence results of the fractional Yamabe problem on $M$ under various geometric assumptions on $X$ and $M$: Firstly, we handle when the boundary $M$ has a point at which the mean curvature is negative. Secondly, we re-encounter the case when $M$ has zero mean curvature and is either non-umbilic or umbilic but non-locally conformally flat. As a result, we replace the geometric restrictions given by González-Qing (Analysis and PDE, 2013) and González-Wang (arXiv:1503.02862) with simpler ones. Also, inspired by Marques (Comm. Anal. Geom., 2007) and Almaraz (Pacific J. Math., 2010), we study lower-dimensional manifolds. Finally, the situation when $X$ is Poincaré-Einstein, $M$ is either locally conformally flat or 2-dimensional is covered under the validity of the positive mass theorem for the fractional conformal Laplacians.

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