Generalized spectral characterization of signed trees

Abstract

Let $T$ be a tree with an irreducible characteristic polynomial $\varphi (x)$ over $\mathbb{Q}$. Let $\Delta (T)$ be the discriminant of $\varphi (x)$. It is proved that if $2^{-\frac{n}{2}}\sqrt{\Delta (T)}$ (which is always an integer) is odd and square free, then every signed tree with underlying graph $T$ is determined by its generalized spectrum.