### Connectivity of random k-nearest-neighbour graphs

#### Abstract

Let P be a Poisson process of intensity one in a square Sn of area n. We construct a random geometric graph Gn,k by joining each point of P to its kk(n) nearest neighbours. Recently, Xue and Kumar proved that if k ≤ 0.074logn then the probability that Gn,k is connected tends to 0 as n → ∞ while, if k ≥ 5.1774logn, then the probability that Gn,k is connected tends to 1 as n → ∞. They conjectured that the threshold for connectivity is k = (1 + o(1))logn. In this paper we improve these lower and upper bounds to 0.3043logn and 0.5139logn, respectively, disproving this conjecture. We also establish lower and upper bounds of 0.7209logn and 0.9967logn for the directed version of this problem. A related question concerns coverage. With Gn,k as above, we surround each vertex by the smallest (closed) disc containing its k nearest neighbours. We prove that if k ≤ 0.7209logn then the probability that these discs cover Sn tends to 0 as n → ∞ while, if k ≥ 0.9967logn, then the probability that the discs cover Sn tends to 1 as n → ∞.

#### Article information

Source
Adv. in Appl. Probab. Volume 37, Number 1 (2005), 1-24.

Dates
First available in Project Euclid: 13 April 2005

http://projecteuclid.org/euclid.aap/1113402397

Digital Object Identifier
doi:10.1239/aap/1113402397

Mathematical Reviews number (MathSciNet)
MR2135151

Zentralblatt MATH identifier
1079.05086

Subjects

#### Citation

Balister, Paul; Bollobás, Béla; Sarkar, Amites; Walters, Mark. Connectivity of random k -nearest-neighbour graphs. Adv. in Appl. Probab. 37 (2005), no. 1, 1--24. doi:10.1239/aap/1113402397. http://projecteuclid.org/euclid.aap/1113402397.

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