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9 votes
1 answer
603 views

Interpolation theory and $C^k$-spaces

Consider the Banach spaces $C^k(M)$ ($k=0,1,2,\dots$), consisting of $k$times continuously differentiable functions $f:M\rightarrow \mathbb{C}$ on a closed manifold $M$ (or just the torus if that ...
Jan Bohr's user avatar
  • 779
-1 votes
1 answer
119 views

Existence of a function with slow growth on derivatives

Does there exist a smooth compactly supported function $$f \in C^{\infty}_c((0,1))$$ such that $$ \|D^k f\|_{L^{2}(0,1)} \leq \left\lfloor{\alpha\,k}\right \rfloor! \quad \forall\, k\in \mathbb N$$ ...
Ali's user avatar
  • 4,125
4 votes
0 answers
117 views

Korovkin subset of $C(\mathbb{T})$

Let $K$ be a compact Hausdorff space and $A$ be a subset of $C(K)$. $A$ is said to be a Korovkin set if for every sequence $(T_n)$ of positive linear operators on $C(K)$, the condition $\|T_n(f)- f\|_\...
Tanmoy Paul's user avatar
4 votes
0 answers
210 views

Inclusion of Hardy spaces

It is well-known that any convergence in $L^p$ for $p \in [1,\infty]$ implies convergence in $L^1_{\text{loc}}$ by Hölder's inequality. It is also known that for $p>1$ it holds that $L^p(\mathbb R)...
Heins Siedentopf's user avatar