Further improvements on asymptotic bounds for codes using distinguished divisors

For a prime power q, let alpha(q) be the standard function in the asymptotic theory of codes, that is, alpha(q)(delta) (6) is the largest asymptotic information rate that can be achieved for a given asymptotic relative minimum distance 6 of q-ary codes. In recent years the Tsfasman-VlAduj-Zink lower bound on alpha(q) (delta) was improved by Elkies, Xing, and Niederreiter and Ozbudak. In this paper we show further improvements on these bounds by using distinguished divisors of global function fields. (c) 2005 Elsevier Inc. All rights reserved.