arXiv subjects

Martino Borello

Publications and source records attributed to Martino Borello.

40 records · Page 3Linked to original sources

arXiv2013

The automorphism group of a self-dual [72,36,16] code is not an elementary abelian group of order 8

The existence of an extremal self-dual binary linear code C of length 72 is a long-standing open problem. We continue the investigation of its automorphism group: looking at the combination of the subcodes fixed by different involutions and doing a computer calculation with Magma, we prove that Aut(C) is not isomorphic to the elementary abelian group of order 8. Combining this with the known results in the literature one obtains that Aut(C) has order at most 5.

cs.IT↗

arXiv2013

The automorphism group of a self-dual [72,36,16] code does not contain S_3, A_4, or D_8

A computer calculation with Magma shows that there is no extremal self-dual binary code C of length 72, whose automorphism group contains the symmetric group of degree 3, the alternating group of degree 4 or the dihedral group of order 8. Combining this with the known results in the literature one obtains that Aut(C) has order at most 5 or isomorphic to the elementary abelian group of order 8.

cs.IT↗

arXiv2013

Automorphism of order 2p in binary self-dual extremal codes of length a multiple of 24

Let C be a binary self-dual code with an automorphism g of order 2p, where p is an odd prime, such that g^p is a fixed point free involution. If C is extremal of length a multiple of 24 all the involutions are fixed point free, except the Golay Code and eventually putative codes of length 120. Connecting module theoretical properties of a self-dual code C with coding theoretical ones of the subcode C(g^p) which consists of the set of fixed points of g^p, we prove that C is a projective F_2 -module if and only if a natural projection of C(g^p) is a self-dual code. We then discuss easy to handle criteria to decide if C is projective or not. As an application we consider in the last part extremal self-dual codes of length 120, proving that their automorphism group does not contain elements of order 38 and 58.

cs.IT↗

arXiv2012

The Automorphism Group of an Extremal [72,36,16] Code does not contain elements of order 6

The existence of an extremal code of length 72 is a long-standing open problem. Let C be a putative extremal code of length 72 and suppose that C has an automorphism g of order 6. We show that C, as an F_2 -module, is the direct sum of two modules, one easily determinable and the other one which has a very restrictive structure. We use this fact to do an exhaustive search and we do not find any code. This proves that the automorphism group of an extremal code of length 72 does not contain elements of order 6.

cs.IT↗