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Extending permutation arrays: improving MOLS bounds

机译:扩展置换数组:改善MOLS范围

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A permutation array (PA) A is a set of permutations on Z(n) = (0, 1, ... , n - 1}, for some n. A PA A has pairwise Hamming distance at least d, if for every pair of permutations sigma and tau in A, there are at least d integers i in Z(n) such that sigma(i) not equal tau(i). Let M(n, d) denote the maximum number of permutations in any PA with pairwise Hamming distance at least d. Recently considerable effort has been devoted to improving known lower bounds for M(n, d) for all n > d > 3. We give a partition and extension operation that enables the production of a new PA A' for M (n + 1, d) from an existing PA A for M (n, d - 1). In particular, this operation allows for improvements for PA's for M(q + 1, q) for powers of prime numbers q, as well as for many other choices of n and d, where n is not a power of a prime. Finally, for prime numbers p, the partition and extension technique provides an asymptotically better lower bound for M(p + 1, p) than that given by current knowledge about mutually orthogonal Latin squares. We prove a new asymptotic lower bound for the set of primes p, namely, M(p + 1, p) >= p(1.5) / 2 - O(p).
机译:排列数组(PA)A是Z(n)=(0,1,...,n-1}上对于某些n的一组排列。PAA的成对汉明距离至少为d,如果每个在A中的一对置换sigma和tau中,Z(n)中至少有d个整数i,使得sigma(i)不等于tau(i)。令M(n,d)表示任何PA中置换的最大数量成对的汉明距离至少为d。最近,人们投入了相当多的精力来改善已知的所有n> d> 3的M(n,d)的下界。我们给出了一种划分和扩展操作,使得能够生产新的PA A对于M(n,d-1),从现有PA A的M(n + 1,d)取',尤其是,此操作可以改进质数q的幂的M(q + 1,q)的PA。 ,以及n和d的许多其他选择,其中n不是素数的幂,最后,对于素数p,划分和扩展技术为M(p + 1,p)提供了渐近更好的下界比目前有关m的知识通常正交的拉丁方格。我们证明了素数p的集合的新渐近下界,即M(p + 1,p)> = p(1.5)/ 2-O(p)。

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