Sign patterns that allow eventual positivity

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Abraham Berman
Minerva Catral
Luz Maria DeAlba
Abed Elhashash
Frank J. Hall
Leslie Hogben
In-Jae Kim
Dale D. Olesky
Pablo Tarazaga
Michael J. Tsatsomeros
Pauline van den Driessche

Abstract

Several necessary or sufficient conditions for a sign pattern to allow eventual positivity are established. It is also shown that certain families of sign patterns do not allow eventual positivity. These results are applied to show that for n ≥ 2, the minimum number of positive entries in an n×n sign pattern that allows eventual positivity is n+1, and to classify all 2×2 and 3×3 sign patterns as to whether or not the pattern allows eventual positivity. A 3 × 3 matrix is presented to demonstrate that the positive part of an eventually positive matrix need not be primitive, answering negatively a question of Johnson and Tarazaga.

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