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arXiv · 2604.21552

Combinatorial aspects of the non-symmetric strong spectral property for graphs

Sara Koljančić·Polona Oblak
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Abstract

In this paper, we investigate the non-symmetric Strong Spectral Property (nSSP) from a combinatorial perspective. To zero-nonzero patterns of matrices we associate directed graphs and study when they require or allow the nSSP, providing a framework that avoids verifying the nSSP for individual matrices. A new combinatorial method is introduced and used to recognise several patterns that require the nSSP. It is shown that loop assignments in double paths play a critical role in establishing this property, and we show that an open question regarding irreducible tridiagonal patterns has a negative answer. We also investigate whether the minimum number of arcs in a directed graph on $n$ vertices that requires the nSSP, is equal to $2n-1$, and confirm this minimum for several specific digraph families.

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Sara Koljančić, Polona Oblak. 2026-04-23. Combinatorial aspects of the non-symmetric strong spectral property for graphs. https://arxiv.org/abs/2604.21552

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