On the Kernel of Z2s\mathbb{Z}_{2^s}-Linear Hadamard Codes

The $\mathbb{Z}_{2^s}$-additive codes are subgroups of $\mathbb{Z}^n_{2^s}$, and can be seen as a generalization of linear codes over $\mathbb{Z}_2$ and $\mathbb{Z}_4$. A $\mathbb{Z}_{2^s}$-linear Hadamard code is a binary Hadamard code which is the Gray map image of a $\mathbb{Z}_{2^s}$-additive code. It is known that the dimension of the kernel can be used to give a complete classification of the $\mathbb{Z}_4$-linear Hadamard codes. In this paper, the kernel of $\mathbb{Z}_{2^s}$-linear Hadamard codes and its dimension are established for $s > 2$. Moreover, we prove that this invariant only provides a complete classification for some values of $t$ and $s$. The exact amount of nonequivalent such codes are given up to $t=11$ for any $s\geq 2$, by using also the rank and, in some cases, further computations

The Poset Metrics That Allow Binary Codes of Codimension m to be m-, (m-1)-, or (m-2)-Perfect

A binary poset code of codimension m (of cardinality 2(n - m), where n is the code length) can correct maximum m errors. All possible poset metrics; that allow codes of codimension m to be m-, (m - 1)-, or (m - 2)-perfect are described. Some general conditions on a poset which guarantee the nonexistence of perfect poset codes are derived; as examples, we prove the nonexistence of r-perfect poset codes for some r in the case of the crown poset and in the case of the union of disjoint chains.X115sciescopu

Matrices uniquely determined by their lonesums (vol 438, pg 3107, 2013)

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