Global well-posedness of the Kirchhoff equation and Kirchhoff systems

This article is devoted to review the known results on global well-posedness for the Cauchy problem to the Kirchhoff equation and Kirchhoff systems with small data. Similar results will be obtained for the initial-boundary value problems in exterior domains with compact boundary. Also, the known results on large data problems will be reviewed together with open problems.Comment: arXiv admin note: text overlap with arXiv:1211.300

Dispersive estimates for Schr\"odinger operators with point interactions in R3\mathbb{R}^3

The study of dispersive properties of Schr\"odinger operators with point interactions is a fundamental tool for understanding the behavior of many body quantum systems interacting with very short range potential, whose dynamics can be approximated by non linear Schr\"odinger equations with singular interactions. In this work we proved that, in the case of one point interaction in $\mathbb{R}^3$, the perturbed Laplacian satisfies the same $L^p-L^q$ estimates of the free Laplacian in the smaller regime $q\in[2,3)$. These estimates are implied by a recent result concerning the $L^p$ boundedness of the wave operators for the perturbed Laplacian. Our approach, however, is more direct and relatively simple, and could potentially be useful to prove optimal weighted estimates also in the regime $q\geq 3$.Comment: To appear on: "Advances in Quantum Mechanics: Contemporary Trends and Open Problems", G. Dell'Antonio and A. Michelangeli eds., Springer-INdAM series 201

Strichartz Estimates for the Vibrating Plate Equation

We study the dispersive properties of the linear vibrating plate (LVP) equation. Splitting it into two Schr\"odinger-type equations we show its close relation with the Schr\"odinger equation. Then, the homogeneous Sobolev spaces appear to be the natural setting to show Strichartz-type estimates for the LVP equation. By showing a Kato-Ponce inequality for homogeneous Sobolev spaces we prove the well-posedness of the Cauchy problem for the LVP equation with time-dependent potentials. Finally, we exhibit the sharpness of our results. This is achieved by finding a suitable solution for the stationary homogeneous vibrating plate equation.Comment: 18 pages, 4 figures, some misprints correcte

L^p boundedness of the wave operator for the one dimensional Schroedinger operator

Given a one dimensional perturbed Schroedinger operator H=-(d/dx)^2+V(x) we consider the associated wave operators W_+, W_- defined as the strong L^2 limits as s-> \pm\infty of the operators e^{isH} e^{-isH_0} We prove that the wave operators are bounded operators on L^p for all 1<p<\infty, provided (1+|x|)^2 V(x) is integrable, or else (1+|x|)V(x) is integrable and 0 is not a resonance. For p=\infty we obtain an estimate in terms of the Hilbert transform. Some applications to dispersive estimates for equations with variable rough coefficients are given.Comment: 26 page

Spectral gap global solutions for degenerate Kirchhoff equations

We consider the second order Cauchy problem $$u''+m(|A^{1/2}u|^2)Au=0, u(0)=u_{0}, u'(0)=u_{1},$$ where $m:[0,+\infty)\to[0,+\infty)$ is a continuous function, and $A$ is a self-adjoint nonnegative operator with dense domain on a Hilbert space. It is well known that this problem admits local-in-time solutions provided that $u_{0}$ and $u_{1}$ are regular enough, depending on the continuity modulus of $m$, and on the strict/weak hyperbolicity of the equation. We prove that for such initial data $(u_{0},u_{1})$ there exist two pairs of initial data $(\overline{u}_{0},\overline{u}_{1})$, $(\widehat{u}_{0},\widehat{u}_{1})$ for which the solution is global, and such that $u_{0}=\overline{u}_{0}+\widehat{u}_{0}$, $u_{1}=\overline{u}_{1}+\widehat{u}_{1}$. This is a byproduct of a global existence result for initial data with a suitable spectral gap, which extends previous results obtained in the strictly hyperbolic case with a smooth nonlinearity $m$.Comment: 16 page

Global Strichartz estimates for an inhomogeneous Maxwell system

We show a global in time Strichartz estimate for the isotropic Maxwell system with divergence free data. On the scalar permittivity and permeability we impose decay assumptions as $|x|\rightarrow\infty$ and a non-trapping condition. The proof is based on smoothing estmates in weighted $L^2$ spaces which follow from corresponding resolvent estimates for the underlying Helmholtz problem

Los efectos de la crisis económica en la molduración y evolución de la opinión pública española ante la inmigración

This paper deals with the effects of economic crisisin the change of attitudes towards immigration, by means of alongitudinal approach via survey data. The analysis of dimensionsand indicators of xenophobia corroborates the negative effect ofeconomic turmoil and labor threat in the increase of xenophobia,in tune with Intergroup Conflict Theory. Although in 2012,rejection to immigration drew back, whereas ambivalence extendedand became tenuous tolerance. In its explanation stands outthe lowering of both real and perceived presence of immigrantpopulation, confirming the effect attributed to the out-group size.Other subjects related to the framing of attitudes add themselves: theimage of immigration transmitted by the mass media and politicaldiscourses, in addition to mutual knowledge (in accordance withthe Theory of Intergroup Contact).Mediante el seguimiento longitudinal de datos demoscópicos,este artículo analiza los efectos de la crisis económica en elcambio de las actitudes hacia la inmigración. El análisis de dimensionese indicadores de xenofobia corrobora el efecto negativo de lainestabilidad y la amenaza económica-laboral en el aumento de laxenofobia, en consonancia con la Teoría del conflicto intergrupal.Si bien, en 2012 el rechazo a la inmigración retrocede, mientras quela ambivalencia se amplía y configura como tenue tolerancia. En suexplicación destaca el descenso de la presencia real y percibida de lapoblación inmigrante, confirmando el efecto atribuido al tamaño delexogrupo. A él se suman otros protagonistas de la molduración delas actitudes: la imagen de la inmigración que trasmiten los mediosde comunicación y los discursos políticos, además del conocimientomutuo (de acuerdo con la Teoría del contacto intergrupal)

Local well-posedness for the space-time Monopole equation in Lorenz gauge

It is known from the work of Czubak that the space-time Monopole equation is locally well-posed in the Coulomb gauge for small initial data in $H^s(\mathbb{R}^2)$ for $s>1/4$. Here we prove local well-posedness for arbitrary initial data in $H^s(\mathbb{R^2})$ with $s>1/4$ in the Lorenz gauge.Comment: To appear in NoDE