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Pathological Phenomena in Denjoy–Carleman Classes
Published online by Cambridge University Press: 20 November 2018
Abstract
Let ${{C}^{M}}$ denote a Denjoy–Carleman class of
${{C}^{\infty }}$ functions (for a given logarithmically-convex sequence
$M\,=\,\left( {{M}_{n}} \right))$. We construct: (1) a function in
${{C}^{M}}\left( \left( -1,\,1 \right) \right)$ that is nowhere in any smaller class; (2) a function on
$\mathbb{R}$ that is formally
${{C}^{M}}$ at every point, but not in
${{C}^{M}}\left( \mathbb{R} \right)$; (3) (under the assumption of quasianalyticity) a smooth function on
${{\mathbb{R}}^{p}}\,\left( p\,\ge \,2 \right)$ that is
${{C}^{M}}$ on every
${{C}^{M}}$ curve, but not in
${{C}^{M}}\left( {{\mathbb{R}}^{p}} \right)$.
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- Copyright © Canadian Mathematical Society 2016
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