The S-Spectrum of Combinations of Idempotents on Two-Sided Quaternionic Banach Algebra
摘要
We establish the relationship between the S-spectrum of fg and the S-spectrum of αf + βg, where f and g are two idempotents on a two-sided quaternionic Banach algebra 𝒜 and α, β ∈ ℝ. We also study the invertibility of linear combinations of idempotents on 𝒜. To do this, we define the complexification 𝒜c of 𝒜, which is regarded as a real Banach algebra, and establish the relationship between the S-spectrum of a ∈ 𝒜 and the spectrum of a as an element of the complexification 𝒜c.