K-theory spectrum

In mathematics, given a ring R, the K-theory spectrum of R is an Ω-spectrum ${\displaystyle K_{R}}$ whose n-th term is given by, writing ${\displaystyle \Sigma R}$ for the suspension of R,

where "+" means the Quillen's + construction. By definition, ${\displaystyle K_{i}(R)=\pi _{i}(K_{R})}$.

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