Finding extremal sets in less than quadratic time

In this work, quadratic residue codes over the ring F"2+uF"2+u^2F"2 with u^3=u are considered. A duality and distance preserving Gray map from F"2+uF"2+u^2F"2 to F"2^3 is defined. By using quadratic double circulant, quadratic bordered double circulant ...

In this work, quadratic double and quadratic bordered double circulant constructions are applied to F 4 + u F 4 as well as to F 4 , and as a result, extremal binary self-dual codes of length 56 and 64 are obtained. The binary extension theorems as well ...

Recently the author and Kimura have considered a construction of doubly-even codes from a given doubly-even code. In this note, we show that the restricutoion of doubly-even can be removed in the above construction. As an application, at least 137 ...