@article {IOPORT.06098831, author = {Campbell, Natalie and Vander Meulen, Kevin N. and Van Tuyl, Adam}, title = {Structure of nilpotent matrices over fields.}, year = {2011}, journal = {ELA. The Electronic Journal of Linear Algebra [electronic only]}, volume = {22}, issn = {1081-3810}, pages = {931-958, electronic only}, publisher = {ILAS - The International Linear Algebra Society c/o Daniel Hershkowitz, Department of Mathematics, Technion - Israel Institute of Techonolgy, Haifa}, abstract = {Summary: A zero-nonzero pattern $A$ is said to be potentially nilpotent over a field $\Bbb F$ if there exists a nilpotent matrix with entries in $\Bbb F$ having zero-nonzero pattern $A$. We explore the construction of potentially nilpotent patterns over a field. We present classes of patterns which are potentially nilpotent over a field $\Bbb F$ if and only if the field $\Bbb F$ contains certain roots of unity. We then introduce some sparse patterns of order n $\geq 4$ which are spectrally arbitrary over $\Bbb C$ but not over $\Bbb R$. We also identify all irreducible patterns of order four which are potentially nilpotent over $\Bbb R$ or $\Bbb C$.}, identifier = {06098831}, }