No Arabic abstract
We prove that a linear d-dimensional Schr{o}dinger equation on $mathbb{R}^d$ with harmonic potential $|x|^2$ and small t-quasiperiodic potential $ipartial_t u -- Delta u + |x|^2 u + epsilon V (tomega, x)u = 0, x in mathbb{R}^d$ reduces to an autonomous system for most values of the frequency vector $omega in mathbb{R}^n$. As a consequence any solution of such a linear PDE is almost periodic in time and remains bounded in all Sobolev norms.
We consider the one-dimensional quantum harmonic oscillator perturbed by a linear operator which is a polynomial of degree $2$ in $(x,-{rm i}partial_x)$, with coefficients quasi-periodically depending on time. By establishing the reducibility results, we describe the growth of Sobolev norms. In particular, the $t^{2s}-$polynomial growth of ${mathcal H}^s-$norm is observed in this model if the original time quasi-periodic equation is reduced to a constant Stark Hamiltonian.
In this article we prove a reducibility result for the linear Schrodinger equation on a Zoll manifold with quasi-periodic in time pseudo-differential perturbation of order less or equal than $1/2$. As far as we know, this is the first reducibility results for an unbounded perturbation of a linear system which is not integrable.
We study the generalized eigenvalue problem on the whole space for a class of integro-differential elliptic operators. The nonlocal operator is over a finite measure, but this has no particular structure and it can even be singular. The first part of the paper presents results concerning the existence of a principal eigenfunction. Then we present various necessary and/or sufficient conditions for the maximum principle to hold, and use these to characterize the simplicity of the principal eigenvalue.
An algebraic lower bound on the energy decay for solutions of the advection-diffusion equation in $mathbb{R}^d$ with $d=2,3$ is derived using the Fourier splitting method. Motivated by a conjecture on mixing of passive scalars in fluids, a lower bound on the $L^2-$ norm of the inverse gradient of the solution is obtained via gradient estimates and interpolation.
Consider a nonlinear Kirchhoff type equation as follows begin{equation*} left{ begin{array}{ll} -left( aint_{mathbb{R}^{N}}| abla u|^{2}dx+bright) Delta u+u=f(x)leftvert urightvert ^{p-2}u & text{ in }mathbb{R}^{N}, uin H^{1}(mathbb{R}^{N}), & end{array}% right. end{equation*}% where $Ngeq 1,a,b>0,2<p<min left{ 4,2^{ast }right}$($2^{ast }=infty $ for $N=1,2$ and $2^{ast }=2N/(N-2)$ for $Ngeq 3)$ and the function $fin C(mathbb{R}^{N})cap L^{infty }(mathbb{R}^{N})$. Distinguishing from the existing results in the literature, we are more interested in the geometric properties of the energy functional related to the above problem. Furthermore, the nonexistence, existence, unique and multiplicity of positive solutions are proved dependent on the parameter $a$ and the dimension $N.$ In particular, we conclude that a unique positive solution exists for $1leq Nleq4$ while at least two positive solutions are permitted for $Ngeq5$.