Skip to main content

All Questions

Filter by
Sorted by
Tagged with
2 votes
0 answers
184 views

Properties of the optimal decomposition for the $K$-functional between $\ell_1$ and $\ell_2$

Background: For any fixed $t> 0$, the $K$-functional defines a norm on the space $\ell_1+\ell_2$: $$ \lVert a\rVert_{K(t)} = \inf\{\lVert a'\rVert_1+ t\lVert a''\rVert_2 : a'\in\ell_1,\ a''\in\...
Clement C.'s user avatar
  • 1,372
2 votes
1 answer
378 views

Does the norm on a sequence space have to be monotone?

Let $\rho:[0,+\infty)^{\mathbb{N}}\to[0,+\infty] $ satisfy the following properties: $\rho(\lambda u)=\lambda\rho( u)$, for every $u\in [0,+\infty)^{\mathbb{N}}$ and $\lambda\ge 0$; $\rho(u+v)\le \...
erz's user avatar
  • 5,529