On potentially nilpotent double star sign patterns
A matrix whose entries come from the set is called a , or . A sign pattern is said to be potentially nilpotent if it has a nilpotent realization. In this paper, the characterization problem for some potentially nilpotent double star sign patterns is discussed. A class of double star sign patterns, denoted by , is introduced. We determine all potentially nilpotent sign patterns in and , and prove that one sign pattern in is potentially stable.