Displaying 961 – 980 of 1497

Showing per page

On the Automorphism Groups of some AG-Codes Based on Ca;b Curves

Shaska, Tanush, Wang, Quanlong (2007)

Serdica Journal of Computing

*Partially supported by NATO.We study Ca,b curves and their applications to coding theory. Recently, Joyner and Ksir have suggested a decoding algorithm based on the automorphisms of the code. We show how Ca;b curves can be used to construct MDS codes and focus on some Ca;b curves with extra automorphisms, namely y^3 = x^4 + 1, y^3 = x^4 - x, y^3 - y = x^4. The automorphism groups of such codes are determined in most characteristics.

On the classification of 3-dimensional non-associative division algebras over p -adic fields

Abdulaziz Deajim, David Grant (2011)

Journal de Théorie des Nombres de Bordeaux

Let p be a prime and K a p -adic field (a finite extension of the field of p -adic numbers p ). We employ the main results in [12] and the arithmetic of elliptic curves over K to reduce the problem of classifying 3-dimensional non-associative division algebras (up to isotopy) over K to the classification of ternary cubic forms H over K (up to equivalence) with no non-trivial zeros over K . We give an explicit solution to the latter problem, which we then relate to the reduction type of the jacobian...

On the Complexity of the Hidden Weighted Bit Function for Various BDD Models

Beate Bollig, Martin Löbbing, Martin Sauerhoff, Ingo Wegener (2010)

RAIRO - Theoretical Informatics and Applications

Ordered binary decision diagrams (OBDDs) and several more general BDD models have turned out to be representations of Boolean functions which are useful in applications like verification, timing analysis, test pattern generation or combinatorial optimization. The hidden weighted bit function (HWB) is of particular interest, since it seems to be the simplest function with exponential OBDD size. The complexity of this function with respect to different circuit models, formulas, and various...

On the computation of covert channel capacity

Eugene Asarin, Cătălin Dima (2010)

RAIRO - Theoretical Informatics and Applications

We address the problem of computing the capacity of a covert channel, modeled as a nondeterministic transducer. We give three possible statements of the notion of “covert channel capacity” and relate the different definitions. We then provide several methods allowing the computation of lower and upper bounds for the capacity of a channel. We show that, in some cases, including the case of input-deterministic channels, the capacity of the channel can be computed exactly (e.g. in the form...

On the computational complexity of centers locating in a graph

Ján Plesník (1980)

Aplikace matematiky

It is shown that the problem of finding a minimum k -basis, the n -center problem, and the p -median problem are N P -complete even in the case of such communication networks as planar graphs with maximum degree 3. Moreover, a near optimal m -center problem is also N P -complete.

On the Construction of Codes from an Asymptotically Good Tower over F8

Caleb McKinley, Shor (2007)

Serdica Journal of Computing

In 2002, van der Geer and van der Vlugt gave explicit equations for an asymptotically good tower of curves over the field F8. In this paper, we will present a method for constructing Goppa codes from these curves as well as explicit constructions for the third level of the tower. The approach is to find an associated plane curve for each curve in the tower and then to use the algorithms of Haché and Le Brigand to find the corresponding Goppa codes.

On the construction of dense lattices with a given automorphisms group

Philippe Gaborit, Gilles Zémor (2007)

Annales de l’institut Fourier

We consider the problem of constructing dense lattices in n with a given non trivial automorphisms group. We exhibit a family of such lattices of density at least c n 2 - n , which matches, up to a multiplicative constant, the best known density of a lattice packing. For an infinite sequence of dimensions n , we exhibit a finite set of lattices that come with an automorphisms group of size n , and a constant proportion of which achieves the aforementioned lower bound on the largest packing density. The algorithmic...

Currently displaying 961 – 980 of 1497