Global existence for the 2D incompressible isotropic elastodynamics for small initial data

We establish the global existence and the asymptotic behavior for the 2D incompressible isotropic elastodynamics for sufficiently small, smooth initial data in the Eulerian coordinates formulation.The main tools used to derive the main results are, on the one hand, a modified energy method to derive the energy estimate and on the other hand, a Fourier transform method with a suitable choice of $Z-$ norm to derive the sharp $L^\infty-$ estimate. We mention that the global existence of the same system but in the Lagrangian coordinates formulation was recently obtained by Lei. Our goal is to improve the understanding of the behavior of solutions. Also we present a different approach to study $2D$ nonlinear wave equations from the point of view in frequency space.Comment: final version for publicatio

Global regularity for the energy-critical NLS on S3\mathbb{S}^3

We establish global existence for the energy-critical nonlinear Schr\"odinger equation on $\mathbb{S}^3$. This follows similar lines to the work on $\mathbb{T}^3$ but requires new extinction results for linear solutions and bounds on the first nonlinear iterate at a Euclidean profile that are adapted to the new geometry.Comment: to appear in the Annales IHP, Analyse non lineaire. arXiv admin note: text overlap with arXiv:1102.5771, arXiv:1101.452