Bulletin of the
Korean Mathematical Society BKMS

Let $K$ be an algebraic number field. If $k$ is the maximal cyclotomic subextension in $K$ then the Schur $K$-group $S(K)$ is obtained from the Schur $k$-group $S(k)$ by scalar extension. In the paper we study projective Schur group $PS(K)$ which is a generalization of Schur group, and prove that a projective Schur $K$-algebra is obtained by scalar extension of a projective Schur $k$-algebra where $k$ is the maximal radical extension in $K$ with mild condition.

Keywords: Schur algebra, projective Schur algebra, projective character

MSC numbers: 16H05, 16S34, 20C25