## Abstract

The minrank of a directed graph G is the minimum rank of a matrix M that can be obtained from the adjacency matrix of G by switching some ones to zeros (i.e., deleting edges) and then setting all diagonal entries to one. This quantity is closely related to the fundamental information-theoretic problems of (linear) index coding (Bar-Yossef et al.), network coding (Effros et al.), and distributed storage (Mazumdar, ISIT, 2014). We prove tight bounds on the minrank of directed Erdos-Rényi random graphs G(n,p) for all regimes of p ∈ [0,1]. In particular, for any constant p, we show that minrk(G) = Θ (n/log n) with high probability, where G is chosen from G(n,p). This bound gives a near quadratic improvement over the previous best lower bound of Ω (√n) (Haviv and Langberg), and partially settles an open problem raised by Lubetzky and Stav. Our lower bound matches the well-known upper bound obtained by the "clique covering" solution and settles the linear index coding problem for random knowledge graphs.

Original language | English (US) |
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Article number | 8304633 |

Pages (from-to) | 6990-6995 |

Number of pages | 6 |

Journal | IEEE Transactions on Information Theory |

Volume | 64 |

Issue number | 11 |

DOIs | |

State | Published - Nov 2018 |

## Keywords

- Index coding
- linear index coding
- minrank

## ASJC Scopus subject areas

- Information Systems
- Computer Science Applications
- Library and Information Sciences