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Finding a norm on $ \mathbb{R}^X $ such that the "natural" embedding of a metric space $ X $...

Note that your embedding map $T$ actually takes values in the subspace $\newcommand{\R}{{\mathbb R}}$ $c_{00}(X;\R)$ of finitely supported functions $X\to\R$. If you merely want a norm on this subspa …
Yemon Choi's user avatar
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7 votes
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Is the matrix induced L1-norm greater than the induced L2-norm?

To avoid ambiguity I will write $\lVert\cdot\rVert_{p\to r}$ for the $\ell_p$-to-$\ell_r$-norm. Note that in general, $\lVert A\rVert_{1\to r} = \max_{1\leq j\leq n} \lVert (Ae_j)\rVert_r$. Let $A$ be …
Yemon Choi's user avatar
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4 votes
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$M_Λ(A) → A ⊗ M_Λ(C)$

The norm on $M_\Lambda(A)$ is the one obtained by identifying it as a vector space (not an algebra) with $\ell^1(\Lambda\times\Lambda, A)$. Similarly, the norm on $M_\Lambda({\mathbb C})$ is the one …
Yemon Choi's user avatar
  • 25.8k