\documentclass[reqno]{amsart} \usepackage{hyperref} \usepackage{amssymb,mathrsfs} \AtBeginDocument{{\noindent\small \emph{Electronic Journal of Differential Equations}, Vol. 2014 (2014), No. 90, pp. 1--15.\newline ISSN: 1072-6691. URL: http://ejde.math.txstate.edu or http://ejde.math.unt.edu \newline ftp ejde.math.txstate.edu} \thanks{\copyright 2014 Texas State University - San Marcos.} \vspace{9mm}} \begin{document} \title[\hfilneg EJDE-2014/90\hfil Self-similar solutions] {Self-similar solutions with compactly supported profile of some nonlinear Schr\"odinger equations} \author[P. B\'egout, J. I. D\'iaz \hfil EJDE-2014/90\hfilneg] {Pascal B\'egout, Jes\'us Ildefonso D\'iaz} % in alphabetical order \address{Pascal B\'egout \newline Institut de Math\'ematiques de Toulouse \& TSE \\ Universit\'e Toulouse I Capitole \\ Manufacture des Tabacs \\ 21, All\'ee de Brienne, 31015 Toulouse Cedex 6, France} \email{Pascal.Begout@math.cnrs.fr} \address{Jes\'us Ildefonso D\'iaz \newline Departamento de Matem\'atica Aplicada\\ Instituto de Matem\'atica Interdisciplinar\\ Universidad Complutense de Madrid, Plaza de las Ciencias, 3, 28040 Madrid, Spain} \email{diaz.racefyn@insde.es} \thanks{Submitted December 9, 2013. Published April 2, 2014.} \subjclass[2000]{35B99, 35A01, 35A02, 35B65, 35J60} \keywords{Nonlinear self-similar Schr\"odinger equation; compact support; \hfill\break\indent energy method} \begin{abstract} ``Sharp localized'' solutions (i.e. with compact support for each given time $t$) of a singular nonlinear type Schr\"odinger equation in the whole space $\mathbb{R}^N$ are constructed here under the assumption that they have a self-similar structure. It requires the assumption that the external forcing term satisfies that $\mathbf{f}(t,x)=t^{-(\mathbf{p}-2)/2}\mathbf{F}(t^{-1/2}x)$ for some complex exponent $\mathbf{p}$ and for some profile function $\mathbf{F}$ which is assumed to be with compact support in $\mathbb{R}^N$. We show the existence of solutions of the form $\mathbf{u}(t,x)=t^{\mathbf{p}/2}\mathbf{U}(t^{-1/2}x)$, with a profile $\mathbf{U}$, which also has compact support in $\mathbb{R}^N$. The proof of the localization of the support of the profile $\mathbf{U}$ uses some suitable energy method applied to the stationary problem satisfied by $\mathbf{U}$ after some unknown transformation. \end{abstract} \maketitle \numberwithin{equation}{section} \newtheorem{theorem}{Theorem}[section] \newtheorem{lemma}[theorem]{Lemma} \newtheorem{definition}[theorem]{Definition} \newtheorem{remark}[theorem]{Remark} \allowdisplaybreaks \section{Introduction and main result} \label{intro} This article deals with the study of \emph{sharp localized} solutions of the nonlinear type Schr\"odinger equation in the whole space $\mathbb{R}^N$, \begin{equation} \label{nls} \mathbf{i}\frac{\partial\mathbf{u}}{\partial t}+\Delta\mathbf{u} =\mathbf{a}|\mathbf{u}|^{-(1-m)}\mathbf{u}+\mathbf{f}(t,x), \end{equation} under the fundamental assumption $m\in (0,1)$ and for different choices of the complex coefficient $\mathbf{a}$. Here we use the notation of bold symbols for complex symbols, $\mathbf{i}^2=-1$ and $\Delta=\sum_{j=1}^N\frac{\partial^2}{\partial x^2_j}$ for the Laplacian in the variables $x$. By the term \emph{sharp localized solutions} we understand solutions which go beyond the so called \emph{localized solutions} considered earlier by many authors. For instance, most of the \emph{localized type solutions} in the previous literature must vanish at infinity in an asymptotic way: $|\mathbf{u}(t,x)|\to 0$ as $|x|\to \infty$. They have been intensively studied mostly when some other structure property is added to the solution. It is the case of the special solutions which receive also other names such as \emph{standing waves, travelling waves, solitons}, etc. Here we are interested on solutions which have a sharper decay when $|x|$ approaches infinity in the sense that we will require the support of the function $\mathbf{u}(t,\cdot)$ to be a compact set of $\mathbb{R}^N$, for any $t\geqslant0$. We recall that equations of the type \eqref{nls} arise in many different contexts: Nonlinear Optics, Quantum Mechanics, Hydrodynamics, etc., and that, for instance, in Quantum Mechanics the main interest concerns the case in which $\operatorname{Re}(\mathbf{a})>0$, $\operatorname{Im}(\mathbf{a})=0$ (here and in which follows $\operatorname{Re}(\mathbf{a})$ is the real part of the complex number $\mathbf{a}$ and $\operatorname{Im}(\mathbf{a})$ is its imaginary part) and that in Nonlinear Optics the $t$ does not represent time but the main scalar variable which appears in the propagation of the wave guide direction (see \cite[p.7]{ak}, \cite[p.517]{MR2169020}). Sometimes equations of the type \eqref{nls} are named as Gross-Pitaevski{\u\i} type of equations in honor of two famous papers by those authors in 1961 (\cite{MR0128907} and \cite{pit}). For some physical details and many references, we refer the reader to the general presentations made in the books \cite{MR2040621,MR2002047,MR2000f:35139}. In most of the papers on equations of the type \eqref{nls}, it is assumed that $m=3$ (the so called \emph{cubic case}). Nevertheless there are applications in which the general case $m>0$ is of interest. For instance, it is the case of the so called \emph{non-Kerr type equations} arising in the study of \emph{optical solitons} (see, e.g., \cite[p.14]{ak}, and following). The case $m\in (0,1)$ has been studied before by other authors but under different points of view: some explicit self-similar solutions (the so called \emph{algebraic solitons}) can be found in \cite{MR2042347} (see also \cite[p.33]{ak}). We also mention here the series of interesting papers by Rosenau and co-authors (\cite{PhysRevLett.101.264101,MR2756172}) in which \emph{sharp localized} solutions are also considered with other type of statements and methods. We also mention that the case $\operatorname{Re}(\mathbf{a})>0$ (which corresponds to the dissipative case, also called defocusing or repulsive case, when $\operatorname{Im}(\mathbf{a})=0)$ must be well distinguished of the so called attractive problem (or also focusing case) in which it is assumed that $\operatorname{Re}(\mathbf{a})<0$ (and $\operatorname{Im}(\mathbf{a})=0)$. See, e.g., \cite{MR2040621,MR2002047,MR2000f:35139} and their references). The case of complex potentials with certain types of singularities, i.e. corresponding to the choice $\operatorname{Im}(\mathbf{a})\ne0$, has been previously considered by several authors, and arises in many different situations (see, for instance, \cite{MR80i:35135,MR2765425,MR2000k:35256,MR1828819} and the references therein). Here we assume that the datum $\mathbf{f}$ is not zero and represents some other physical magnitude which may arise in the possible coupling with some different phenomenon: see the different chapters of Part IV of the book \cite{MR2000f:35139}, the interaction phenomena between long waves and short waves (\cite{MR0463715,MR2339808,urr} and their references), etc. Obviously, the property of the compactness of the support of $\mathbf{u}(t,\cdot)$ requires the assumption that ``the support'' of the datum function $\mathbf{f}(t,\cdot)$ is a compact set of $\mathbb{R}^N$, for a.e. $t>0$. Because of that, the qualitative property we consider in this paper can be understood as a ``finite speed of propagation property'' typical of linear wave equations. We point out that our treatment is very different than other ``propagation properties'' studied previously in the literature for Schr\"odinger equations which are formulated in terms of the spectrum of the solutions. See, e.g., the so called Anderson localization (\cite{MR0129917}), \cite{MR797050}, etc. One of the main reasons of the study of \emph{sharp localized} solutions arises from the fact that, if we assume for the moment $\mathbf{f}\equiv\mathbf{0}$, then \[ \frac{\partial}{\partial t}|\mathbf{u}|^2+\operatorname{div}\mathbf{J }=2\operatorname{Im}(\mathbf{a})|\mathbf{u}|^{m+1}, \] where \[ \mathbf{J}:=\big(\mathbf{u}\overline{\nabla\mathbf{u}} -\overline{\mathbf{u}}\nabla\mathbf{u}\big) =-2\operatorname{Re}(\mathbf{i} \overline{\mathbf{u}} \nabla\mathbf{u}), \] ($\overline{\mathbf{u}}$ denotes the conjugate of the complex function $\mathbf{u}$) and so we get (at least formally) that \[ \frac12\frac{\mathrm{d}}{\mathrm{d} t}\int_{\mathbb{R}^N}|\mathbf{u}(t,x)|^2\mathrm{d} x =\operatorname{Im}(\mathbf{a})\int_{\mathbb{R}^N}|\mathbf{u}(t,x)|^{m+1}\mathrm{d} x. \] Note that if $\operatorname{Im}(\mathbf{a})\neq0$ then there is no mass conservation. For instance, this is the case studied by \cite{MR2765425} where they prove that actually the solution vanishes after a finite time, once that $m\in(0,1)$. More generally, it is easy to see that the two following conservation laws hold, once $a\in\mathbb{R}$ and $\mathbf{f}\equiv\mathbf{0}$: if $\mathbf{u}(t)\in\mathbf{H^1}(\mathbb{R}^N)\cap\mathbf{L^{m+1}}(\mathbb{R}^N)$ then we have the mass conservation $\frac{\mathrm{d}}{\mathrm{d} t}\|\mathbf{u}(t)\|_{\mathbf{L^2}(\mathbb{R}^N)}^2=0$; moreover, if $\mathbf{u}(t)\in\mathbf{H^2}(\mathbb{R}^N)\cap\mathbf{L^{2m}} (\mathbb{R}^N)$ then $\mathbf{u}(t)\in\mathbf{L^{m+1}}(\mathbb{R}^N)$ and we have conservation of energy $\frac{\mathrm{d}}{\mathrm{d} t}E\big(\mathbf{u}(t)\big)=0$, where \[ E\big(\mathbf{u}(t)\big)=\frac12\|\nabla\mathbf{u}(t)\|_{\mathbf{L^2}(\mathbb{R}^N)}^2 +\frac{a}{m+1}\|\mathbf{u}(t)\|_{\mathbf{L^{m+1}}(\mathbb{R}^N)}^{m+1}. \] Indeed, in the first case, $\Delta\mathbf{u}(t)\in\mathbf{H^{-1}}(\mathbb{R}^N)$ and $|\mathbf{u}(t)|^{-(1-m)}\mathbf{u}(t)\in\mathbf{L^\frac{m+1}{m}}(\mathbb{R}^N)$. It follows from the equation \eqref{nls} that $\frac{\partial\mathbf{u}(t)}{\partial t}\in\mathbf{H^{-1}}(\mathbb{R}^N) +\mathbf{L^\frac{m+1}{m}}(\mathbb{R}^N)$ and since $\left(\mathbf{H^1}(\mathbb{R}^N)\cap\mathbf{L^{m+1}}(\mathbb{R}^N)\right)^\star =\mathbf{H^{-1}}(\mathbb{R}^N)+\mathbf{L^\frac{m+1}{m}}(\mathbb{R}^N)$, it follows that we may take the duality product of equation~\eqref{nls} with $\mathbf{i}\mathbf{u}(t)$, from which the mass conservation follows. In the same way, since $\mathbf{u}(t)\in\mathbf{L^2}(\mathbb{R}^N)\cap\mathbf{L^{2m}}(\mathbb{R}^N)$ and $00$ and $\operatorname{Im}(\mathbf{a})=0)$, it is possible to get some estimates on the support of solutions $\mathbf{u}(t,x)$ showing that the probability $|\mathbf{u}(t,x)|^2$ to localize a particle is zero outside of a compact set of $\mathbb{R}^N$. The natural structure for searching self-similar solutions is based on the transformation $\lambda\longmapsto\mathbf{u_\lambda}$, where for $\lambda>0$, $\mathbf{p}\in\mathbb{C}$ and $\mathbf{u}\in\mathbf{C}\big((0,\infty);\mathbf{L^1_\mathrm{loc}} (\mathbb{R}^N)\big)$, we define \begin{equation} \label{ula} \mathbf{u_\lambda}(t,x)=\lambda^{-\mathbf{p}}\mathbf{u}(\lambda^2t,\lambda x), \quad \forall t>0, \text{ for a.e. } x\in\mathbb{R}^N. \end{equation} Recall that since $\mathbf{p}\in\mathbb{C}$, it follows that $\lambda^{\mathbf{p}}:=\mathbf{e}^{\mathbf{p}\ln\lambda} =e^{\operatorname{Re}(\mathbf{p})\ln\lambda}\mathbf{e}^{\mathbf{i}\operatorname{Im} (\mathbf{p})\ln\lambda}=\lambda^{\operatorname{Re}(\mathbf{p})}\mathbf{e}^{\mathbf{i}\operatorname{Im} (\mathbf{p})\ln\lambda}$ and that $|\lambda^{\mathbf{p}}|=\lambda^{\operatorname{Re}(\mathbf{p})}$. Our main assumption on the datum $\mathbf{f}$ is that \begin{equation} \label{fla} \mathbf{f}(t,x)=\lambda^{-(\mathbf{p}-2)}\mathbf{f}(\lambda^2t,\lambda x), \quad \forall\lambda>0, \end{equation} for some $\mathbf{p}\in\mathbb{C}$, for any $t>0$ and almost every $x\in\mathbb{R}^N$, or equivalently, that \begin{equation} \label{eqprof} \mathbf{f}(t,x)=t^{\frac{\mathbf{p}-2}{2}}\mathbf{F}\big(\frac{x}{\sqrt t}\big), \end{equation} for any $t>0$ and almost every $x\in\mathbb{R}^N$, where $\mathbf{F}=\mathbf{f}(1)$. It is easy to build functions $\mathbf{f}$ satisfying \eqref{fla}. Indeed, for any given function $\mathbf{F}$, we define $\mathbf{f}$ by \eqref{eqprof}. Then $\mathbf{f}(1)=\mathbf{F}$ and $\mathbf{f}$ satisfies \eqref{fla}. Finally, if we assume $\operatorname{Re}(\mathbf{p})=\frac2{1-m}$ then a direct calculation show that if $\mathbf{u}$ is a solution to~\eqref{nls} then for any $\lambda>0$, $\mathbf{u_\lambda}$ is also a solution to~\eqref{nls}, and conversely. We easily check that if $\mathbf{u}$ satisfies the invariance property $\mathbf{u}=\mathbf{u_\lambda}$, for any $\lambda>0$, then \begin{equation} \label{eqprou} \mathbf{u}(t,x)=t^{\mathbf{p}/2}\mathbf{U}\Big(\frac{x}{\sqrt t}\Big), \end{equation} for any $t>0$ and almost every $x\in\mathbb{R}^N$, where $\mathbf{U}=\mathbf{u}(1)$. Thus, we arrive to the following notion: \begin{definition} \label{defselsim} \rm Let $00$, $\mathbf{u_\lambda}=\mathbf{u}$, where $\mathbf{u_\lambda}$ is defined by \eqref{ula}. In this cases, $\mathbf{u}(1)$ is called the \emph{profile} of $\mathbf{u}$ and is denoted by $\mathbf{U}$. \end{definition} It follows from equation \eqref{nls} and \eqref{eqprou} that $\mathbf{U}$ satisfies \begin{equation} \label{U} -\Delta\mathbf{U} + \mathbf{a}|\mathbf{U}|^{-(1-m)}\mathbf{U} - \frac{\mathbf{i}\mathbf{p}}{2}\mathbf{U} + \frac{\mathbf{i}}{2}x.\nabla\mathbf{U} = -\mathbf{F}, \end{equation} in $\mathscr{D}'(\mathbb{R}^N)$, where $\mathbf{F}=\mathbf{f}(1)$. Conversely, if $\mathbf{U}\in\mathbf{L^2_\mathrm{loc}}(\mathbb{R}^N)$ verifies \eqref{U}, in $\mathscr{D}'(\mathbb{R}^N)$, then the function $\mathbf{u}$ defined by \eqref{eqprou} belongs to $\mathbf{C}\big((0,\infty);\mathbf{L^2_\mathrm{loc}}(\mathbb{R}^N)\big)$ and is a self-similar solution to~\eqref{nls}, where $\mathbf{f}$ is defined by \eqref{eqprof} and satisfies \eqref{fla}. It is useful to introduce the unknown transformation \begin{equation} \label{gU} \mathbf{g}(x)=\mathbf{U}(x)\mathbf{e}^{-\mathbf{i}|x|^2/8}. \end{equation} Then for any $m\in\mathbb{R}$, $\mathbf{p}\in\mathbb{C}$ and $\mathbf{U}\in\mathbf{L^2_\mathrm{loc}}(\mathbb{R}^N)$, $\mathbf{U}$ is a solution to \eqref{U} in $\mathscr{D}'(\mathbb{R}^N)$ if and only if $\mathbf{g}\in\mathbf{L^2_\mathrm{loc}}(\mathbb{R}^N)$ is a solution to \begin{equation} \label{g} -\Delta\mathbf{g} + \mathbf{a}|\mathbf{g}|^{-(1-m)}\mathbf{g} - \mathbf{i}\frac{N+2\mathbf{p}}{4}\mathbf{g} - \frac1{16}|x|^2\mathbf{g} = -\mathbf{F}\mathbf{e}^{-\mathbf{i}\frac{|\cdot|^2}{8}}, \end{equation} in $\mathscr{D}'(\mathbb{R}^N)$. It will be convenient to study~\eqref{g} instead of~\eqref{U}. Indeed, formally, if we multiply \eqref{g} by $\pm\overline{\mathbf{g}}$ or $\pm\mathbf{i}\overline{\mathbf{g}}$, integrate by parts and take the real part, one obtains some positive or negative quantities. But the same method applied to \eqref{U} gives (at least directly) nothing because of the term $\mathbf{i} x.\nabla\mathbf{U}$. Notice that if $\mathbf{p}\in\mathbb{C}$ is such that $\operatorname{Re}(\mathbf{p})=\frac2{1-m}$ and if $\mathbf{f}\in\mathbf{C}\big((0,\infty);\mathbf{L^2}(\mathbb{R}^N)\big)$ and satisfies \eqref{fla} with $\mathbf{f}(t_0)$ compactly supported for some $t_0>0$, then it follows from~\eqref{fla} that for any $t>0$, $\operatorname{supp}\mathbf{f}(t)$ is compact. Moreover, from~\eqref{eqprou}, if $\mathbf{u}$ is a self-similar solution of \eqref{nls} and if $\operatorname{supp}\mathbf{U}$ is compact then for any $t>0$, $\operatorname{supp}\mathbf{u}(t)$ is compact. As a matter of fact, it is enough to have that $\mathbf{u}(t_0)$ is compactly supported for some $t_0>0$ to have that $\mathbf{u}$ satisfies \eqref{thmmain1} below and $\operatorname{supp}\mathbf{u}(t)$ is compact, for any $t>0$. Indeed, $\mathbf{U}=\mathbf{u}(1)$ satisfies \eqref{U} and by \eqref{eqprou}, $\operatorname{supp}\mathbf{U}$ and $\operatorname{supp}\mathbf{u}(t)$ are compact for any $t>0$. Let $\mathbf{g}$ be defined by~\eqref{gU}. Then $\mathbf{g}$ is a solution compactly supported to~\eqref{g} and it follows the results of Section~\ref{eus} below that $\mathbf{g}\in\mathbf{H^2_\mathrm{c}}(\mathbb{R}^N)$. By~\eqref{gU}, we obtain that $\mathbf{U}\in\mathbf{H^2_\mathrm{c}}(\mathbb{R}^N)$ and we deduce easily from \eqref{eqprou} that $\mathbf{u}$ satisfies \eqref{thmmain1}. The main result of this paper reads as follows. \begin{theorem} \label{thmmain} Let $00$, $\operatorname{supp}\mathbf{u}(t)$ is compact. In particular, $\mathbf{u}$ is a strong solution and verifies~\eqref{nls} for any $t>0$ in $\mathbf{L^2}(\mathbb{R}^N)$, and so almost everywhere in $\mathbb{R}^N$. \item \label{thmmainb} Let $R>0$. For any $\varepsilon>0$, there exists $\delta_0=\delta_0(R,\varepsilon,|\mathbf{a}|,|\mathbf{p}|,N,m)>0$ satisfying the following property$:$ if $\operatorname{supp}\mathbf{f}(1)\subset\overline B(0,R)$ and if $\|\mathbf{f}(1)\|_{\mathbf{L^2}(\mathbb{R}^N)}\leqslant\delta_0$ then the profile $\mathbf{U}$ of the solution obtained above verifies $\operatorname{supp}\mathbf{U}\subset K(\varepsilon)\subset\overline B(0,R+\varepsilon)$, where \[ K(\varepsilon)=\Big\{x\in\mathbb{R}^N;\; \exists y\in\operatorname{supp}\mathbf{f}(1) \text{ such that } |x-y|\leqslant\varepsilon \Big\}, \] which is compact. \item \label{thmmainc} Let $R_0>0$. Assume now further that $\operatorname{Re}(\mathbf{a})>0$, $\operatorname{Im}(\mathbf{a})=0$ and \[ 4\operatorname{Im}(\mathbf{p})+2\sqrt{4\operatorname{Im}^2(\mathbf{p})+2} \geqslant R_0^2. \] Then the solution is unique in the set of functions $\mathbf{C}\big((0,\infty);\mathbf{L^2_\mathrm{c}}(\mathbb{R}^N)\big)$ whose profile $\mathbf{V}$ satisfies $\operatorname{supp}\mathbf{V}\subset\overline B(0,R_0)$. \end{enumerate} \end{theorem} In contrast with many other papers on self-similar solutions of equations dealing with exponents $m>1$ (see \cite{MR99d:35149,MR99f:35185,MR1745480} and their references), in this paper we do not prescribe any initial data $\mathbf{u}(0)$ to \eqref{nls} since we are only interested on any solution $\mathbf{u}(t)$ by an external source $\mathbf{f}(t)$ compactly supported. Moreover, we point out that if $\mathbf{u}\in\mathbf{C}\big([0,\infty);\mathbf{L^q}(\mathbb{R}^N)\big)$ is a self-similar solution to~\eqref{nls}, for some $00$, $\|\mathbf{u}(t)\|_{\mathbf{L^q}(\mathbb{R}^N)} =t^{\frac{1}{1-m}+\frac{N}{2q}}\|\mathbf{U}\|_{\mathbf{L^q}(\mathbb{R}^N)}$, implying necessarily that $\mathbf{u}(0)=\mathbf{0}$. On the other hand, notice that if $\mathbf{u}\in\mathbf{C}\big([0,\infty);\mathscr{D}'(\mathbb{R}^N)\big)$ is a self-similar solution to~\eqref{nls} then one cannot expect to have $\mathbf{u}(0)\in\mathbf{L^q}(\mathbb{R}^N)$, unless $\mathbf{u}(0)=\mathbf{0}$. Indeed, we would have $\mathbf{u_\lambda}(0)=\mathbf{u}(0)$ in $\mathbf{L^q}(\mathbb{R}^N)$ and for any $\lambda>0$, $\|\mathbf{u}(0)\|_{\mathbf{L^q}(\mathbb{R}^N)}=\lambda^{\frac{2}{1-m} +\frac{N}{q}}\|\mathbf{u}(0)\|_{\mathbf{L^q}(\mathbb{R}^N)}$ and again we deduce that necessarily $\mathbf{u}(0)=\mathbf{0}$. More generally, the set of functions $\mathbf{u}$ satisfying the invariance property, \[ \forall\lambda>0, \text{ for a.e. } x\in\mathbb{R}^N, \quad \mathbf{u_\lambda}(x):=\lambda^{-\mathbf{p}}\mathbf{u}(\lambda x)=\mathbf{u}(x), \] and lying in $\mathbf{L^q}(\mathbb{R}^N)$ is reduced to $\mathbf{0}$. In the special case of self-similar solution, the above arguments show that if $\mathbf{f}\equiv\mathbf{0}$, $a\in\mathbb{R}$ and $\mathbf{u}\in\mathbf{C}\big((0,\infty);\mathbf{L^2_\mathrm{c}}(\mathbb{R}^N)\big)$ then necessarily $\mathbf{u}(t)=0$, for any $t>0$. Indeed, if $\mathbf{u}\in\mathbf{C}\big((0,\infty);\mathbf{L^2_\mathrm{c}}(\mathbb{R}^N)\big)$ is a self-similar solution to~\eqref{nls} then its profile $\mathbf{U}$ belongs to $\mathbf{L^2}(\mathbb{R}^N)$ and $\mathbf{u}\in\boldsymbol C^2((0;\infty)\times\mathbb{R}^N)$ (see Section~\ref{eus} below). So for any $t>0$, we can multiply the above equation by $-\mathbf{i}\overline{\mathbf{u}}(t)$, integrate by parts over $\mathbb{R}^N$ and take the real part. We then deduce the mass conservation, $\frac{\mathrm{d}}{\mathrm{d} t}\|\mathbf{u}(t)\|_{\mathbf{L^2}(\mathbb{R}^N)}^2=0$, which yields with the above identity, \begin{gather*} \|\mathbf{U}\|_{\mathbf{L^2}(\mathbb{R}^N)} =\|\mathbf{u}(t)\|_{\mathbf{L^2}(\mathbb{R}^N)}=t^{\frac{1}{1-m} +\frac{N}{4}}\|\mathbf{U}\|_{\mathbf{L^2}(\mathbb{R}^N)}, \end{gather*} for any $t>0$. Hence the result. As a matter of fact, if $\ell\in\{0,1,2\}$ and if $\mathbf{u}\in\mathbf{C}\big((0,\infty);\mathbf{H^\ell}(\mathbb{R}^N)\big)$ is a self-similar solution to~\eqref{nls} then one easily deduces from~\eqref{eqprou} that actually $\lim_{t\searrow0}\|\mathbf{u}(t)\|_{\mathbf{H^\ell}(\mathbb{R}^N)}=0$. We also mention here that our treatment of sharp localized solutions has some indirect connections with the study of the ``unique continuation property''. Indeed, we are showing that this property does not hold when $m\in(0,1)$, in contrast to the case of linear and other type of nonlinear Schr\"odinger equations (see, e.g., \cite{MR1980854,urr}). The paper is organized as follows. In the next section, we introduce some notation and give general versions of the main results (Theorems~\ref{thmsta} and \ref{thmG}). In Section~\ref{eus}, we recall some existence, uniqueness, \emph{a priori} bound and smoothness results of solutions to equation~\eqref{g} associated to the evolution equation \eqref{nls}. Finally, Section \ref{proof} is devoted to the proofs of the mentioned results, which we carry out by improving some energy methods presented in \cite{MR2002i:35001}. \section{Notation and general versions of the main result} \label{not} Before stating our main results, we will indicate here some of the notation used throughout. For $1\leqslant p\leqslant\infty$, $p'$ is the conjugate of $p$ defined by $\frac1p+\frac1{p'}=1$. We denote by $\overline\Omega$ the closure of a nonempty subset $\Omega\subseteq\mathbb{R}^N$ and by $\Omega^\mathrm{c}=\mathbb{R}^N\setminus\Omega$ its complement. We note $\omega\Subset\Omega$ to mean that $\overline\omega\subset\Omega$ and that $\overline\omega$ is a compact subset of $\mathbb{R}^N$. Unless specified, any function lying in a functional space $\big(\mathbf{L^p}(\Omega)$, $\mathbf{W^{m,p}}(\Omega)$, etc\big) is supposed to be a complex-valued function ($\mathbf{L^p}(\Omega;\mathbb{C})$, $\mathbf{W^{m,p}}(\Omega;\mathbb{C})$, etc). For a functional space $\mathbf{E}\subset\mathbf{L^1_\mathrm{loc}}(\Omega;\mathbb{C})$, we denote by $\mathbf{E_\mathrm{c}}=\big\{\mathbf{f}\in\mathbf{E};\operatorname{supp}\mathbf{f}\Subset\Omega\big\}$. For a Banach space $\mathbf{E}$, we denote by $\mathbf{E}^\star$ its topological dual and by $\langle\cdot,\cdot\rangle_{\mathbf{E}^\star,\mathbf{E}}\in\mathbb{R}$ the $\mathbf{E}^\star-\mathbf{E}$ duality product. In particular, for any $\mathbf{T}\in\mathbf{L^{p'}}(\Omega)$ and $\boldsymbol{\varphi}\in\mathbf{L^p}(\Omega)$ with $1\leqslant p<\infty$, $\langle\mathbf{T},\boldsymbol{\varphi}\rangle_{\mathbf{L^{p'}}(\Omega), \mathbf{L^p}(\Omega)}=\operatorname{Re}\int_\Omega\mathbf{T}(x) \overline{\boldsymbol{\varphi}(x)}\mathrm{d} x$. For $x_0\in\mathbb{R}^N$ and $r>0$, we denote by $B(x_0,r)$ the open ball of $\mathbb{R}^N$ of center $x_0$ and radius $r$, by $\mathbb{S}(x_0,r)$ its boundary and by $\overline B(x_0,r)$ its closure. As usual, we denote by $C$ auxiliary positive constants, and sometimes, for positive parameters $a_1,\ldots,a_n$, write $C(a_1,\ldots,a_n)$ to indicate that the constant $C$ continuously depends only on $a_1,\ldots,a_n$ (this convention also holds for constants which are not denoted by ``$C$''). Now, we state the precise notion of solution. \begin{definition} \label{defsols} \rm Let $\Omega$ be a nonempty bounded open subset of $\mathbb{R}^N$, let $(\mathbf{a},\mathbf{b},\mathbf{c})\in\mathbf{\mathbb{C}^3}$, let $00$. If $\rho_0>\operatorname{dist}(x_0,\Gamma)$ then assume further that $\mathbf{g}\in\mathbf{H^1_0}(\Omega)$. Assume now that $\mathbf{G}_{|\Omega\cap B(x_0,\rho_0)}\equiv\mathbf{0}$. Then $\mathbf{g}_{|\Omega\cap B(x_0,\rho_\mathrm{max})}\equiv\mathbf{0}$, where \begin{equation} \label{thmsta1} \begin{aligned} \rho_\mathrm{max}^\nu &=\Big(\rho_0^\nu-CM^2\max\{1,\frac{1}{L^2}\}\max\{\rho_0^{\nu-1},1\} \\ &\quad \times\min_{\tau\in(\frac{m+1}{2},1]}\big\{\frac{E(\rho_0)^{\gamma(\tau)} \max\{b(\rho_0)^{\mu(\tau)},b(\rho_0)^{\eta(\tau)}\}}{2\tau-(1+m)}\big\}\Big)_+, \end{aligned} \end{equation} where \begin{gather*} E(\rho_0)=\|\nabla\mathbf{g}\|_{\mathbf{L^2}(\Omega\cap B(x_0,\rho_0))}^2, \quad b(\rho_0)=\|\mathbf{g}\|_{\mathbf{L^{m+1}}(\Omega\cap B(x_0,\rho_0))}^{m+1}, \\ k=2(1+m)+N(1-m), \quad \nu=\frac{k}{m+1}>2, \end{gather*} and where \begin{gather*} \gamma(\tau)=\frac{2\tau-(1+m)}{k}\in(0,1), \quad \mu(\tau)=\frac{2(1-\tau)}{k}, \quad \eta(\tau)=\frac{1-m}{1+m}-\gamma(\tau)>0. \end{gather*} for any $\tau\in(\frac{m+1}{2},1]$. \end{theorem} Here and in what follows, $r_+=\max\{0,r\}$ denotes the positive part of the real number $r$. \begin{remark} \label{rmkthmsta} \rm If the solution is too ``large'', it may happen that $\rho_\mathrm{max}=0$ and so the above result is not consistent. A sufficient condition to observe a localizing effect is that the solution is small enough, in a suitable sense. We give below a sufficient condition on the data $\mathbf{a}\in\mathbb{C}$, $\mathbf{p}\in\mathbb{C}$ and $\mathbf{G}$ to have $\rho_\mathrm{max}>0$. \end{remark} \begin{theorem} \label{thmG} Let $\Omega\subset B(0,R)$ be a nonempty bounded open subset of $\mathbb{R}^N$, let $00$. If $\rho_1>\operatorname{dist}(x_0,\Gamma)$ then assume further that $\mathbf{g}\in\mathbf{H^1_0}(\Omega)$. Then there exist two positive constants $E_\star>0$ and $\varepsilon_\star>0$ satisfying the following property: let $\rho_0\in(0,\rho_1)$ and assume that $\|\nabla\mathbf{g}\|_{\mathbf{L^2}(\Omega\cap B(x_0,\rho_1))}^20$ and $M>0$ are given by Theorem~\ref{thmsta}. The dependence on $1/\delta$ means that if $\delta$ goes to $0$ then $E_\star$ and $\varepsilon_\star$ may be very large. Note that $p=1/\gamma(1)$, where $\gamma$ is the function defined in Theorem~\ref{thmsta}. \end{remark} \section{Existence, uniqueness and smoothness} \label{eus} We recall the following results which are taken from other works by the authors \cite[Theorems 2.4, 2.6 and 2.12]{Beg-Di4}. Let $\Omega\subset B(0,R)$ be a nonempty bounded open subset of $\mathbb{R}^N$, let $00$, $\operatorname{Re}(\mathbf{b})\geqslant0$ and $c\geqslant0$. Then for any $\mathbf{F}\in\mathbf{L^2}(\Omega)$, equation \[ -\Delta\mathbf{U} - \mathbf{i} a|\mathbf{U}|^{-(1-m)}\mathbf{U} - \mathbf{i}\mathbf{b}\mathbf{U} + \mathbf{i} cx.\nabla\mathbf{U} = \mathbf{F}, \quad \text{in } \mathscr{D}'(\Omega), \] admits at most one global very weak solution compact with support $\mathbf{U}\in\mathbf{L^2_\mathrm{c}}(\Omega)$. \end{theorem} \begin{proof} Let $\mathbf{U_1},\mathbf{U_2}\in\mathbf{L^2_\mathrm{c}}(\Omega)$ be two global very weak solutions both compactly supported to the above equation. By the results above, one has $\mathbf{U_1},\mathbf{U_2}\in\mathbf{H^2_\mathrm{c}}(\Omega)$. Setting $\mathbf{g_1}=\mathbf{U_1}\mathbf{e}^{-\mathbf{i} c\frac{|\cdot|^2}{4}}$ and $\mathbf{g_2}=\mathbf{U_2}\mathbf{e}^{-\mathbf{i} c\frac{|\cdot|^2}{4}}$, a straightforward calculation shows that (see also the beginning of Section~\ref{proof} below) $\mathbf{g_1},\mathbf{g_2}\in\mathbf{H^2_\mathrm{c}}(\Omega)$ satisfy \[ -\Delta\mathbf{g}+\widetilde{\mathbf{a}}|\mathbf{g}|^{-(1-m)}\mathbf{g}+\widetilde{\mathbf{b}}\mathbf{g}+\widetilde c V^2\mathbf{g} = \widetilde{\mathbf{F}}, \text{ in } \mathbf{L^2}(\Omega), \] where $\widetilde{\mathbf{a}}=-\mathbf{i} a$, $\widetilde{\mathbf{b}}=-\mathbf{i}(\mathbf{b}+\frac{cN}{2})$, $\widetilde c=-\frac{c^2}{4}$, $V(x)=|x|$ and $\widetilde{\mathbf{F}}=\mathbf{F}\mathbf{e}^{-\mathbf{i} c\frac{|\cdot|^2}{4}}$. Note that, \begin{gather*} \widetilde{\mathbf{a}}\neq0, \quad \operatorname{Re}(\widetilde{\mathbf{a}})=0, \\ \operatorname{Re}(\widetilde{\mathbf{a}}\,\overline{\widetilde{\mathbf{b}}}) =\operatorname{Re}\Big(a\big(\overline{\mathbf{b}+\frac{cN}{2}}\big)\Big) =a\operatorname{Re}(\mathbf{b})+\frac12acN\geqslant0, \\ \operatorname{Re}\big(\widetilde{\mathbf{a}}\,\overline{\widetilde c}\big) =\frac{ac^2}{4}\operatorname{Re}(\mathbf{i})=0. \end{gather*} Then it follows from (1) of Theorem~2.10 in \cite{Beg-Di4} that $\mathbf{g_1}=\mathbf{g_2}$ and hence, $\mathbf{U_1}=\mathbf{U_2}$. \end{proof} \begin{remark} \label{moreuni} \rm Notice that uniqueness for self-similar solution is relied to uniqueness for \eqref{g}. Using Theorem~2.10 in \cite{Beg-Di4}, we can show that the uniqueness of self-similar solutions to equation~\eqref{nls} holds in the class of functions $\mathbf{C}\big((0,\infty);\mathbf{L^2_\mathrm{c}}(\mathbb{R}^N)\big)$ when, for instance, $\operatorname{Re}(\mathbf{a})=0$ and $\operatorname{Im}(\mathbf{a})<0$ (Theorem~\ref{thmuni}). These hypotheses are the same as in \cite{MR2765425}. We point out that it seems possible to adapt the uniqueness method of \cite[Theorem 2.10]{Beg-Di4} to obtain other criteria of uniqueness. \end{remark} \begin{remark} \label{rmkpoi} \rm In the proof of uniqueness of Theorem~\ref{thmmain}, we will use the Poincar\'e's inequality~\eqref{poibt}. This estimate can be improved in several ways. For instance, for any $x_0\in\mathbb{R}^N$ and any $R>0$, we have \begin{equation}\label{rmkpoi1} \|\mathbf{u}\|_{\mathbf{L^2}(B(x_0,R))}\leqslant \frac{2R}{\pi}\|\nabla\mathbf{u}\|_{\mathbf{L^2}(B(x_0,R))}, \end{equation} which is substantially better than \eqref{poibt}, since $2/\pi <1<\sqrt2$. Actually, \eqref{rmkpoi1} holds for any $\mathbf{u}\in\mathbf{H^1}\big(B(x_0,R)\big)$ such that \[ \int_{B(x_0,R)}\mathbf{u}(x)\mathrm{d} x=\mathbf{0}, \] and $\dfrac{\partial^2\mathbf{u}}{\partial x_j\partial x_k}\in\mathbf{L^\infty} \big(B(x_0,R)\big)$, for any $(j,k)\in[\![ 1,N]\!]\times[\![ 1,N]\!]$. See \cite{MR0117419} for more details. \end{remark} \section{Proofs of the localization properties} \label{proof} We start by pointing out that if $\Omega\subseteq\mathbb{R}^N$ is a nonempty open subset and if $00$ small enough, in case of Theorem~\ref{thmG}. The key estimate which leads to desired local behaviour is that the exponent $\alpha$ arising in \eqref{etoile} satisfies that $\alpha\in(0,1)$. Although the main steps to prove \eqref{etoile} follow the same steps already indicated in the monograph \cite{MR2002i:35001}, it turns out that the concrete case of the systems of scalar equations generated by the Schr\"odinger operator does not fulfill the assumptions imposed in \cite{MR2002i:35001} for the case of systems of nonlinear equations. The extension of the method which applied to the system associated to the complex Schr\"odinger operator is far to be trivial and it was the main object of \cite{MR2876246}. Unfortunately, the extension of the method presented in \cite{MR2876246} is not enough to be applied to the fundamental equation of the present paper (i.e. \eqref{g} or \eqref{eq2}) mainly due to the presence of the source term $-c^2|x|^2g$. A sharper version of the energy method, also applicable to a different type of nonlinear complex Schr\"odinger type equations (for instance containing a Hartree-Fock type nonlocal term), was developed in \cite{Beg-Di5}, where the applicability of the energy method was reduced to prove a certain local energy balance. Such a local balance will be proved here in the following lemma. Thanks to that, the proofs of Theorems~\ref{thmsta} and \ref{thmG} are then a corollary of Theorems~2.1 and 2.2 in \cite{Beg-Di5}. \begin{lemma} \label{lemest} Let $\Omega\subset B(0,R)$ be a nonempty bounded open subset of $\mathbb{R}^N$, let $00$, if $\mathbf{G}_{|\Omega\cap B(x_0,\rho_\star)}\in\mathbf{L^2} \big(\Omega\cap B(x_0,\rho_\star)\big)$ then we have \begin{equation}\label{lemest1} \begin{aligned} &\|\nabla\mathbf{g}\|_{\mathbf{L^2}(\Omega\cap B(x_0,\rho))}^2 +L\|\mathbf{g}\|_{\mathbf{L^{m+1}}(\Omega\cap B(x_0,\rho))}^{m+1} +L\|\mathbf{g}\|_{\mathbf{L^2}(\Omega\cap B(x_0,\rho))}^2 \\ &\leqslant M\Big(\big|\int_{\Omega\cap\mathbb{S}(x_0,\rho)} \mathbf{g}\overline{\nabla\mathbf{g}}.\frac{x-x_0}{|x-x_0|}\mathrm{d}\sigma\big| +\int_{\Omega\cap B(x_0,\rho)}|\mathbf{G}(x)\mathbf{g}(x)|\mathrm{d} x\Big), \end{aligned} \end{equation} for every $\rho\in[0,\rho_\star)$, where it is additionally assumed that $\mathbf{g}\in\mathbf{H^1_0}(\Omega)$ if $\rho_\star>\operatorname{dist}(x_0,\Gamma)$. \end{lemma} \begin{proof} Let $x_0\in\Omega$ and let $\rho_\star>0$. Let $\sigma$ be the surface measure on a sphere and set for every $\rho\in[0,\rho_*)$, \begin{gather*} I(\rho)=\big|\int_{\Omega\cap\mathbb{S}(x_0,\rho)} \mathbf{g}\overline{\nabla\mathbf{g}}.\frac{x-x_0}{|x-x_0|}\mathrm{d}\sigma\big|, \quad J(\rho)=\int_{\Omega\cap B(x_0,\rho)}|\mathbf{G}(x)\mathbf{g}(x)|\mathrm{d} x, \\ w(\rho)=\int_{\Omega\cap\mathbb{S}(x_0,\rho)}\mathbf{g}\overline{\nabla\mathbf{g}}. \frac{x-x_0}{|x-x_0|}\mathrm{d}\sigma, \quad I_{\rm Re}(\rho)=\operatorname{Re}\big(w(\rho)\big), \quad I_{\rm Im}(\rho)=\operatorname{Im}\big(w(\rho)\big). \end{gather*} By taking as test function $\mathbf{\widetilde\varphi_n}(x)=\psi_n(|x-x_0|)\mathbf{\widetilde g}(x)$, where $\mathbf{\widetilde g}$ is the extension by $0$ of $\mathbf{g}$ on $\Omega^\mathrm{c}\cap B(x_0,\rho_0)$ and $\psi_n$ is the cut-off function \[ \forall t\in\mathbb{R},\quad \psi_n(t)= \begin{cases} 1, & \text{if } |t|\in[0,\rho-\frac{1}{n}], \\ n(\rho-|t|), & \text{if } |t|\in(\rho-\frac{1}{n},\rho), \\ 0, & \text{if } |t|\in[\rho,\infty), \end{cases} \] it can be proved (see \cite[Theorem 3.1]{Beg-Di5}) that $I,J,I_{\rm Re},I_{\rm Im}\in C([0,\rho_*);\mathbb{R})$ and, by passing to the limit as $n \to \infty$, that \begin{equation} \label{prooflemest-2} \begin{aligned} &\|\nabla\mathbf{g}\|_{\mathbf{L^2}(\Omega\cap B(x_0,\rho))}^2 +\operatorname{Re}(\mathbf{a})\|\mathbf{g}\|_{\mathbf{L^{m+1}}(\Omega\cap B(x_0,\rho))}^{m+1} +\operatorname{Re}(\mathbf{b})\|\mathbf{g}\|_{\mathbf{L^2}(\Omega\cap B(x_0,\rho))}^2 \\ \\ &+\operatorname{Re}(\mathbf{c})\||x|\mathbf{g}\|_{\mathbf{L^2}(\Omega\cap B(x_0,\rho))}^2\\ &=I_{\rm Re}(\rho)+\operatorname{Re} \Big(\int_{\Omega\cap B(x_0,\rho)}\mathbf{G}(x)\overline{\mathbf{g}(x)}\mathrm{d} x\Big), \end{aligned} \end{equation} \begin{equation} \label{prooflemest-1} \begin{aligned} &\operatorname{Im}(\mathbf{a})\|\mathbf{g}\|_{\mathbf{L^{m+1}}(\Omega\cap B(x_0,\rho))}^{m+1} +\operatorname{Im}(\mathbf{b})\|\mathbf{g}\|_{\mathbf{L^2}(\Omega\cap B(x_0,\rho))}^2 +\operatorname{Im}(\mathbf{c})\||x|\mathbf{g}\|_{\mathbf{L^2}(\Omega\cap B(x_0,\rho))}^2 \\ \\ &=I_{\rm Im}(\rho)+\operatorname{Im} \Big(\int_{\Omega\cap B(x_0,\rho)}\mathbf{G}(x)\overline{\mathbf{g}(x)}\mathrm{d} x\Big), \end{aligned} \end{equation} for any $\rho\in[0,\rho_\star)$. From these estimates, we obtain \begin{equation} \label{prooflemest1} \begin{aligned} &\Big|\|\nabla\mathbf{g}\|_{\mathbf{L^2}(B(x_0,\rho))}^2 +\operatorname{Re}(\mathbf{a})\|\mathbf{g}\|_{\mathbf{L^{m+1}}(B(x_0,\rho))}^{m+1} +\operatorname{Re}(\mathbf{b})\|\mathbf{g}\|_{\mathbf{L^2}(B(x_0,\rho))}^2 \\ &+\operatorname{Re}(\mathbf{c})\||x|\mathbf{g}\|_{\mathbf{L^2}(B(x_0,\rho))}^2\Big|\\ &\leqslant I(\rho)+J(\rho), \end{aligned} \end{equation} \begin{equation}\label{prooflemest2} \begin{aligned} &|\operatorname{Im}(\mathbf{a})|\|\mathbf{g}\|_{\mathbf{L^{m+1}}(B(x_0,\rho))}^{m+1} +|\operatorname{Im}(\mathbf{b})|\|\mathbf{g}\|_{\mathbf{L^2}(B(x_0,\rho))}^2 +|\operatorname{Im}(\mathbf{c})|\||x|\mathbf{g}\|_{\mathbf{L^2}(B(x_0,\rho))}^2\\ &\leqslant I(\rho)+J(\rho), \end{aligned} \end{equation} for any $\rho\in[0,\rho_\star)$. Let $A>1$ to be chosen later. We multiply \eqref{prooflemest2} by $A$ and sum the result with \eqref{prooflemest1}. This leads to \begin{equation} \label{prooflemest3} \begin{aligned} &\|\nabla\mathbf{g}\|_{\mathbf{L^2}(B(x_0,\rho))}^2 +A_1\|\mathbf{g}\|_{\mathbf{L^{m+1}}(B(x_0,\rho))}^{m+1} +A_2\|\mathbf{g}\|_{\mathbf{L^2}(B(x_0,\rho))}^2 +\operatorname{Re}(\mathbf{c})\||x|\mathbf{g}\|_{\mathbf{L^2}(B(x_0,\rho))}^2\\ &\leqslant2A\big(I(\rho)+J(\rho)\big), \end{aligned} \end{equation} where \begin{gather*} A_1 =\begin{cases} \operatorname{Re}(\mathbf{a}), & \text{if } \operatorname{Re}(\mathbf{a})>0, \\ A|\operatorname{Im}(\mathbf{a})|-|\operatorname{Re}(\mathbf{a})|, & \text{if } \operatorname{Re}(\mathbf{a})\leqslant0, \end{cases} \\ A_2 = A|\operatorname{Im}(\mathbf{b})|-|\operatorname{Re}(\mathbf{b})|. \end{gather*} But \eqref{prooflemest3} yields, \begin{equation} \label{prooflemest4} \begin{aligned} &\|\nabla\mathbf{g}\|_{\mathbf{L^2}(B(x_0,\rho))}^2 +A_1\|\mathbf{g}\|_{\mathbf{L^{m+1}}(B(x_0,\rho))}^{m+1} +\big(A_2-R^2|\operatorname{Re}(\mathbf{c})|\big)\|\mathbf{g}\|_{\mathbf{L^2}(B(x_0,\rho))}^2\\ &\leqslant2A\big(I(\rho)+J(\rho)\big) \end{aligned} \end{equation} We choose $A=A(R,|\mathbf{a}|,|\mathbf{b}|,|\mathbf{c}|)$ large enough to have $A|\operatorname{Im}(\mathbf{a})|-|\operatorname{Re}(\mathbf{a})|\geqslant1$ (when $\operatorname{Re}(\mathbf{a})\leqslant0)$ and $A_2-R^2|\operatorname{Re}(\mathbf{c})|\geqslant1$. Then~\eqref{lemest1} comes from \eqref{prooflemest4} with $L=\min\big\{A_1,1\big\}$ and $M=2A$. Note that $L=L(R,|\mathbf{a}|,|\mathbf{b}|,|\mathbf{c}|)$ and $M=M(R,|\mathbf{a}|,|\mathbf{b}|,|\mathbf{c}|)$. This concludes the proof. \end{proof} \begin{remark} \label{rmklemest} \rm When $\rho_\star\leqslant\operatorname{dist}(x_0,\Gamma)$ and $\mathbf{G}\in\mathbf{L^2_\mathrm{loc}}(\Omega)$, one may easily obtain \eqref{prooflemest-2}--\eqref{prooflemest-1} without the technical \cite[Theorem 3.1]{Beg-Di5}. Indeed, it follows from \cite[Proposition 4.5]{MR2876246} that $\mathbf{g}\in\mathbf{H^2_\mathrm{loc}}(\Omega)$, so that equation~\eqref{eq2} makes sense in $\mathbf{L^2_\mathrm{loc}}(\Omega)$ and almost everywhere in $\Omega$. Thus, if $\rho_\star\leqslant\operatorname{dist}(x_0,\Gamma)$ then $\mathbf{g}_{|B(x_0,\rho)}\in\mathbf{H^2}\big(B(x_0,\rho)\big)$ and \eqref{prooflemest-2} \big(respectively, \eqref{prooflemest-1}\big) is obtained by multiplying \eqref{eq2} by $\overline{\mathbf{g}}$ (respectively, by $\overline{\mathbf{i}\mathbf{g}})$, integrating by parts over $B(x_0,\rho)$ and taking the real part. \end{remark} \begin{proof}[Proof of Theorem~\ref{thmmain}] Let $R>0$. Let $\varepsilon>0$ and let $\mathbf{f}\in\mathbf{C}\big((0,\infty);\mathbf{L^2}(\mathbb{R}^N)\big)$ satisfying~\eqref{fla} and $\operatorname{supp}\mathbf{f}(1)\subset\overline B(0,R)$. Let $M_0$ be the constant in~\eqref{new}. Let $\mathbf{b}=-\mathbf{i}\frac{N+2\mathbf{p}}{4}$, $\mathbf{c}=-\frac1{16}$ and $\mathbf{G}=-\mathbf{f}(1)\mathbf{e}^{-\mathbf{i}\frac{|\cdot|^2}{8}}$. Note that $\operatorname{Im}(\mathbf{a})\leqslant0$, $\operatorname{Im}(\mathbf{b})=-\frac{N(1-m)+4}{4(1-m)}<0$ and $\operatorname{Im}(\mathbf{c})=0$. In addition, if $\operatorname{Re}(\mathbf{a})\leqslant0$ then $\operatorname{Im}(\mathbf{a})<0$. It follows that the existence result of Section~\ref{eus} applies to equation~\eqref{g}: let $\mathbf{g}\in\mathbf{H^1_0}(B(0,2R+2\varepsilon))\cap\mathbf{H^2}(B(0,2R+2\varepsilon))$ be such a solution to \eqref{g} and \eqref{dir}. We apply Theorem~\ref{thmsta} with $\rho_0=2\varepsilon$. By \eqref{new}, there exists $\delta_0=\delta_0(R,\varepsilon,|\mathbf{a}|,|\mathbf{b}|,|\mathbf{c}|,N,m)>0$ such that if $\|\mathbf{f}(1)\|_{\mathbf{L^2}(\mathbb{R}^N)}\leqslant\delta_0$ then $\rho_\mathrm{max}\geqslant\varepsilon$. Set $K=\operatorname{supp}\mathbf{f}(1)=\operatorname{supp}\mathbf{G}$. Let $x_0\in\overline{K(2\varepsilon)^\mathrm{c}}\cap B(0,2R+2\varepsilon)$. Let $y\in B(x_0,2\varepsilon)$ and let $z\in K$. By definition of $K(2\varepsilon)$, $\operatorname{dist}(\overline{K(2\varepsilon)^\mathrm{c}},K)=2\varepsilon$. We then have \[ 2\varepsilon=\operatorname{dist}(\overline{K(2\varepsilon)^\mathrm{c}},K) \le|x_0-z|\le|x_0-y|+|y-z|<2\varepsilon+|y-z|. \] It follows that for any $z\in K$, $|y-z|>0$, so that $y\not\in K$. This means that $B(x_0,2\varepsilon)\cap K=\emptyset$, for any $x_0\in\overline{K(2\varepsilon)^\mathrm{c}}\cap B(0,2R+2\varepsilon)$. By Theorem~\ref{thmsta} we deduce that for any $x_0\in\overline{K(2\varepsilon)^\mathrm{c}}\cap B(0,2R+2\varepsilon)$, $\mathbf{g}_{\left|B(x_0,\varepsilon)\right.}\equiv\mathbf{0}$. By compactness, $\overline{K(\varepsilon)^\mathrm{c}}\cap B(0,2R+2\varepsilon)$ may be covered by a finite number of sets $B(x_0,\varepsilon)\cap B(0,2R+2\varepsilon)$ with $x_0\in\overline{K(2\varepsilon)^\mathrm{c}}$. It follows that $\mathbf{g}|_{K(\varepsilon)^\mathrm{c}\cap B(0,2R+2\varepsilon)}\equiv\mathbf{0}$. This means that $\operatorname{supp}\mathbf{g}\subset K(\varepsilon)\subset B(0,2R+2\varepsilon)$. We then extend $\mathbf{g}$ by $\mathbf{0}$ outside of $B(0,2R+2\varepsilon)$. Thus, $\mathbf{g}\in\mathbf{H^2_\mathrm{c}}(\mathbb{R}^N)$ is a solution to \eqref{g} in $\mathbb{R}^N$. Now, let $\mathbf{U}=\mathbf{g}\mathbf{e}^{\mathbf{i}\frac{|\cdot|^2}{8}}$ and let for any $t>0$, $\mathbf{u}(t)=t^{\mathbf{p}/2}\mathbf{U}(\frac{\cdot }{\sqrt t})$. It follows that $\operatorname{supp}\mathbf{U}=\operatorname{supp}\mathbf{g}\subset K(\varepsilon)$, $\mathbf{U}\in\mathbf{H^2_\mathrm{c}}(\mathbb{R}^N)$ and $\mathbf{U}$ is a solution to \eqref{U} in $\mathbb{R}^N$. By \eqref{eqprou}, $\mathbf{u}$ verifies \eqref{thmmain1} and is a solution to~\eqref{nls} in $(0,\infty)\times\mathbb{R}^N$ with $\mathbf{u}(1)=\mathbf{U}$ compactly supported in $K(\varepsilon)$. By Definition~\ref{defselsim}, $\mathbf{u}$ is self-similar and still by \eqref{eqprou}, $\operatorname{supp}\mathbf{u}(t)$ is compact for any $t>0$. Hence Properties~\ref{thmmaina} and \ref{thmmainb}. It remains to show Property~\ref{thmmainc}. Let $R_0>0$ and assume further that $\operatorname{Re}(\mathbf{a})>0$, $\operatorname{Im}(\mathbf{a})=0$ and $00\Big\}$. But, \[ \frac{1}{2R_0^2}+\frac12\operatorname{Im}(\mathbf{p})-\frac{R_0^2}{16} =\frac{1}{16R_0^2}\left(-R_0^4+8\operatorname{Im}(\mathbf{p})R_0^2+8\right)\geqslant0, \] when \[ 0\leqslant R_0^2\leqslant4\operatorname{Im}(\mathbf{p}) +2\sqrt{4\operatorname{Im}^2(\mathbf{p})+2}. \] It follows that $\mathbf{g_1}=\mathbf{g_2}$ which implies that $\mathbf{U_1}=\mathbf{U_2}$ and for any $t>0$, $\mathbf{u_1}(t)=\mathbf{u_2}(t)$. This completes the proof. \end{proof} \subsection*{Acknowledgements} J. I. D\'iaz was partially supported by project MTM2011-26119 of the DGISPI (Spain) and the Research Group MOMAT (Ref. 910480) supported by UCM. 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