In two hundred years many innovations in communication have helped people all
over the globe to connect. However, we still deal with the fundamental problem of
communication, reproducing at one point either exactly or approximately a message
send from another point. From this problem, new branches of mathematics were created,
such as Coding Theory and Information Theory.
In the first part of this thesis, we study "nilpotent codes" and approach the problem of
permutation equivalence between codes. In addition, we give conditions for monomial
equivalence between codes in a group algebra; in particular to cyclic codes. In the
case of minimal nilpotent codes a sufficient codition is given for being permutation
equivalent to abelian codes.
The second part is devoted to present a different method of computing the number of
simple components of a twisted group algebra. In addition, we compute the centrally
primitive idempotents of the twisted group algebras of a cyclic group and in the last
part we provide an example of idempotents in twisted group algebras.