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Hypoelliptic Bi-Invariant Laplacians on Infinite Dimensional Compact Groups
Published online by Cambridge University Press: 20 November 2018
Abstract
On a compact connected group $G$, consider the infinitesimal generator
$-L$ of a central symmetric Gaussian convolution semigroup
${{\left( {{\mu }_{t}} \right)}_{t>0}}$. Using appropriate notions of distribution and smooth function spaces, we prove that
$L$ is hypoelliptic if and only if
${{\left( {{\mu }_{t}} \right)}_{t>0}}$ is absolutely continuous with respect to Haar measure and admits a continuous density
$x\mapsto {{\mu }_{t}}\left( x \right),t>0$, such that
${{\lim }_{t\to 0}}t\log {{\mu }_{t}}\left( e \right)=0$. In particular, this condition holds if and only if any Borel measure
$u$ which is solution of
$Lu=0$ in an open set
$\Omega $ can be represented by a continuous function in
$\Omega $. Examples are discussed.
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- Research Article
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- Copyright © Canadian Mathematical Society 2006
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