Spectrum of a C*-algebra
= Spectrum of a C*-algebra
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In the context of C*-algebras, the **spectrum** of an element \\( a \\) in a C*-algebra \\( \\mathcal\{A\} \\) refers to the set of scalars \\( \\lambda \\) in the complex numbers \\( \\mathbb\{C\} \\) such that the operator \\( a - \\lambda I \\) is not invertible, where \\( I \\) is the identity element in \\( \\mathcal\{A\} \\).