English

Balance and pattern distribution of sequences derived from pseudorandom subsets of $\mathbb{Z}_q$

Number Theory 2021-11-11 v1 Combinatorics

Abstract

Let qq be a positive integer and S={x0,x1,,xT1}Zq={0,1,,q1}\mathcal{S}=\left\{x_0,x_1,\ldots,x_{T-1}\right\}\subseteq\mathbb{Z}_q=\{0,1,\ldots,q-1\} with 0x0<x1<<xT1q1.0\leq x_0<x_1<\ldots< x_{T-1}\leq q-1. We derive from S\mathcal{S} three (finite) sequences. 1. For an integer M2M\geq 2 let (sn)(s_n) be the MM-ary sequence defined by \begin{eqnarray*} s_n\equiv x_{n+1}-x_n \bmod M, \qquad n=0,1,\ldots, T-2. \end{eqnarray*} 2. For an integer m2m\geq 2 let (tn)(t_n) be the binary sequence defined by \begin{eqnarray*} t_n=\left\{\begin{array}{ll} 1, & \hbox{if } 1\leq x_{n+1}-x_n\leq m-1, \\ 0, & \hbox{otherwise}, \end{array}\right. \qquad n=0,1,\ldots, T-2. \end{eqnarray*} 3. Let (un)(u_n) be the characteristic sequence of S\mathcal{S}, \begin{eqnarray*} u_n=\left\{\begin{array}{ll} 1, & \hbox{if } n\in \mathcal{S}, \\ 0, & \hbox{otherwise}, \end{array}\right. \qquad n=0,1,\ldots, q-1. \end{eqnarray*} We study the balance and pattern distribution of the sequences (sn)(s_n), (tn)(t_n) and (un)(u_n). For sets S\mathcal{S} with desirable pseudorandom properties, more precisely, sets with low correlation measures, we show the following: 1. The sequence (sn)(s_n) is (asymptotically) balanced and has uniform pattern distribution if TT is of smaller order of magnitude than qq. 2. The sequence (tn)(t_n) is balanced and has uniform pattern distribution if TT is approximately (1121/(m1))q\left(1-\frac{1}{2^{1/(m-1)}}\right)q. 3. The sequence (un)(u_n) is balanced and has uniform pattern distribution if TT is approximately q2\frac{q}{2}. These results are motivated by earlier results for the sets of quadratic residues and primitive roots modulo a prime. We unify these results and derive many further (asymptotically) balanced sequences with uniform pattern distribution from pseudorandom subsets.

Keywords

Cite

@article{arxiv.2111.05662,
  title  = {Balance and pattern distribution of sequences derived from pseudorandom subsets of $\mathbb{Z}_q$},
  author = {Huaning Liu and Arne Winterhof},
  journal= {arXiv preprint arXiv:2111.05662},
  year   = {2021}
}