7 research outputs found
Relative generalized hamming weights and extended weight polynomials of almost affine codes
This is a post-peer-review, pre-copyedit version of an article published in Lecture Notes in Computer Science, International Castle Meeting on Coding Theory and Applications ICMCTA 2017: Coding Theory and Applications, 207-216. The final authenticated version is available online at: http://dx.doi.org/10.1007/978-3-319-66278-7_17 .This paper is devoted to giving a generalization from linear
codes to the larger class of almost affine codes of two different results.
One such result is how one can express the relative generalized Hamming
weights of a pair of codes in terms of intersection properties between the
smallest of these codes and subcodes of the largest code. The other result
tells how one can find the extended weight polynomials, expressing the
number of codewords of each possible weight, for each code in an infinite
hierarchy of extensions of a code over a given alphabet. Our tools will
be demi-matroids and matroids
Weight enumeration of codes from finite spaces
We study the generalized and extended weight enumerator of the q-ary Simplex code and the q-ary first order Reed-Muller code. For our calculations we use that these codes correspond to a projective system containing all the points in a finite projective or affine space. As a result from the geometric method we use for the weight enumeration, we also completely determine the set of supports of subcodes and words in an extension code
Defining the q-analogue of a matroid
\u3cp\u3eThis paper defines the q-analogue of a matroid and establishes several properties like duality, restriction and contraction. We discuss possible ways to define a q-matroid, and why they are (not) cryptomorphic. Also, we explain the motivation for studying q-matroids by showing that a rank metric code gives a q-matroid.\u3c/p\u3
The extended and generalized rank weight enumerator of a code
This paper investigates the rank weight enumerator of a code over L, where L is a finite extension of a field K. This is a generalization of the case where K = F_q and L = F_{q^m} of Gabidulin codes to arbitrary characteristic. We use the notion of counting polynomials, to define the (extended) rank weight enumerator, since in this generality the set of codewords of a given rank weight is no longer finite. Also the extended and generalized rank weight enumerator are studied in analogy with previous work on codes with respect to the Hamming metric
On defining generalized rank weights
\u3cp\u3eThis paper investigates the generalized rank weights, with a definition implied by the study of the generalized rank weight enumerator. We study rank metric codes over L, where L is a finite extension of a field K. This is a generalization of the case where K = Fq and L = Fqm of Gabidulin codes to arbitrary characteristic. We show equivalence to previous definitions, in particular the ones by Kurihara-Matsumoto-Uyematsu [12, 13], Oggier-Sboui [16] and Ducoat [6]. As an application of the notion of generalized rank weights, we discuss codes that are degenerate with respect to the rank metric.\u3c/p\u3