A Gagliardo-Nirenberg inequality, with application to duality-based a posteriori error estimation in the L1 norm

Abstract

We establish the Gagliardo-Nirenberg-type multiplicative interpolation inequality \[ \|v\|_{{\rm L}1(\mathbb{R}^n)} \leq C \|v\|^{1/2}_{{\rm Lip}'(\mathbb{R}^n)} \|v\|^{1/2}_{{\rm BV}(\mathbb{R}^n)}\qquad \forall v \in {\rm BV}(\mathbb{R}^n), \] where $C$ is a positive constant, independent of $v$. We then use a local version of this inequality to derive an a posteriori error bound in the ${\rm L}1(\Omega')$ norm, with $\bar\Omega' \subset\Omega=(0,1)^n$, for a finite-element approximation to a boundary value problem for a first-order linear hyperbolic equation, under the limited regularity requirement that the solution to the problem belongs to ${\rm BV}(\Omega)$.\ud \ud Dedicated to Professor Boško S Jovanovic on the occasion of his sixtieth birthda