1
vote
2answers
62 views

What does this theorem mean?

Let $(V,\|\cdot\|)$ be a finite-dimensional normed space. Define $\|T\|_\mathrm{op}=\sup\{\|T(x)\|:\|x\|≦1\}$, for all linear operators on $V$ Define $\Omega$ to be the set of all invertible linear ...
0
votes
0answers
24 views

What's an application of that the set of invertible linear operators is open?

Let $V$ be a finite-dimensional normed space. Let $\Omega$ be the set of all invertible linear operators on $V$. Then, $\Omega$ is open in $(\mathscr{L}(V),||\cdot||_{op})$ and $f:\Omega\rightarrow ...
4
votes
2answers
135 views

Why a norm and not some other function that defines a metric?

If one defines on a $\mathbb{R},\mathbb{C}$-vector space a norm this gives rise to a metric. Why are particularly mappings that satisfy the norm axioms so important that in every book for beginners on ...