Butson full propelinear codes
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In this paper we study Butson Hadamard matrices, and codes over finite rings coming from these matrices in logarithmic form, called BH-codes. We introduce a new morphism of Butson Hadamard matrices through a generalized Gray map on the matrices in logarithmic form, which is comparable to the morphism given in a recent note of Ó Catháin and Swartz. That is, we show how, if given a Butson Hadamard matrix over the k^ th roots of unity, we can construct a larger Butson matrix over the ℓ^ th roots of unity for any ℓ dividing k, provided that any prime p dividing k also divides ℓ. We prove that a ℤ_p^s-additive code with p a prime number is isomorphic as a group to a BH-code over ℤ_p^s and the image of this BH-code under the Gray map is a BH-code over ℤ_p (binary Hadamard code for p=2). Further, we investigate the inherent propelinear structure of these codes (and their images) when the Butson matrix is cocyclic. Some structural properties of these codes are studied and examples are provided.
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