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for questions involving inequalities, upper and lower bounds.

4 votes
Accepted

Proving a certain $ C^{*} $-algebraic inequality

The following argument seems easier, but there might be a still more fundamental one. Notice that $ \phi: A^{\sim} \to \mathbb{C} $ above is also a $ C^{*} $-algebraic homomorphism. As $ C^{*} $-alge …
Transcendental's user avatar
8 votes
1 answer
352 views

Proving a certain $ C^{*} $-algebraic inequality

Let $ A $ be a non-unital $ C^{*} $-algebra. Is there an ‘elementary’ way to prove, for all $ (a,\lambda) \in A \times \mathbb{C} $, the inequality $$ |\lambda| \leq \sup_{b \in A, ~ \| b \| \leq 1} \ …
Transcendental's user avatar
1 vote
0 answers
117 views

Finding the infimum of the range of a certain non-negative function associated to a $ C^{*} ...

Let $ A $ be a non-trivial $ C^{*} $-algebra and $ n \in \mathbb{N} $. Setting $ \mathcal{D} \stackrel{\text{df}}{=} A^{n} \setminus \{ (0_{A},\ldots,0_{A}) \} $, we can define a function $ f: \mathca …
Transcendental's user avatar