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Results tagged with ca.classical-analysis-and-odes
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user 170237
Special functions, orthogonal polynomials, harmonic analysis, ordinary differential equations (ODE's), differential relations, calculus of variations, approximations, expansions, asymptotics.
6
votes
1
answer
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Littlewood-Paley theory and dense property of Sobolev spaces [duplicate]
I'm learning the Littlewood-Paley theory by myself and I encounter the following claim:
Pick a smooth function $\chi$ such that:
$$\chi(\xi) = \begin{cases}
1 &|\xi| \leq \frac{1}{2}\\
0 &|\xi| \geq …
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