Constacyclic codes as invariant subspaces

Constacyclic codes are generalizations of the familiar linear cyclic codes. In this paper constacyclic codes over a finite field F are regarded as invariant subspaces of Fn with respect to a suitable linear operator. By applying standard techniques from linear algebra one can derive properties of these codes which generalize several well-known results for cyclic codes, such as the various lower bounds for the minimum distance.