arXiv subjects

Amir Moradifam

Publications and source records attributed to Amir Moradifam.

39 records · Page 3Linked to original sources

arXiv2008

Simultaneous preconditioning and symmetrization of non-symmetric linear systems

Motivated by the theory of self-duality which provides a variational formulation and resolution for non self-adjoint partial differential equations \cite{G1, G2}, we propose new templates for solving large non-symmetric linear systems. The method consists of combining a new scheme that simultaneously preconditions and symmetrizes the problem, with various well known iterative methods for solving linear and symmetric problems. The approach seems to be efficient when dealing with certain ill-conditioned, and highly non-symmetric systems.

math.NA↗

arXiv2007

Bessel potentials and optimal Hardy and Hardy-Rellich inequalities

We give necessary and sufficient conditions on a pair of positive radial functions V and W on a ball B of radius R in R^n,$n \geq 1$, so that the following inequalities hold for all $u \in C_{0}^{\infty}(B)$: $\int_{B}V(x)|\nabla u |^{2}dx \geq \int_{B} W(x)u^2dx$, and $\int_{B}V(x)|Δu |^{2}dx \geq \int_{B} W(x)|\nabla u|^{2}dx+(n-1)\int_{B}(\frac{V(x)}{|x|^2}-\frac{V_r(|x|)}{|x|})|\nabla u|^2dx$. This characterization makes a very useful connection between Hardy-type inequalities and the oscillatory behaviour of certain ordinary differential equations, and helps in the identification of a large number of such couples (V, W) - that we call Bessel pairs -as well as the best constants in the corresponding inequalities. This allows us to improve, extend, and unify many results -old and new- about Hardy and Hardy-Rellich type inequalities, such as those obtained by Caffarelli-Kohn-Nirenberg, Brezis-Vazquez, Wang-Willem, Adimurthi-Chaudhuri-Ramaswamy, Filippas-Tertikas, Adimurthi-Grossi -Santra, Tertikas-Zographopoulos, and Blanchet-Bonforte-Dolbeault-Grillo-Vasquez.

math.AP↗

arXiv2007

On the best possible remaining term in the Hardy Inequality

We give a necessary and sufficient condition on a radially symmetric potential $V$ on $Ω$ that makes it an admissible candidate for an improved Hardy inequality of the following form: \begin{equation}\label{gen-hardy.0} \hbox{$\int_Ω|\nabla u |^{2}dx - (\frac{n-2}{2})^{2} \int_Ω\frac{|u|^{2}}{|x|^{2}}dx\geq c\int_Ω V(|x|)|u|^{2}dx$ \quad for all $u \in H^{1}_{0}(Ω)$.} \end{equation}

math.AP↗