Abstract:
Finite groups are said to be isospectral if they have the same sets of the orders of elements. We investigate almost simple groups $H$ with socle $S$, where $S$ is a finite simple symplectic or orthogonal group over a field of odd characteristic. We prove that if $H$ is isospectral to $S$, then $H/S$ presents a $2$-group. Also we give a criterion for isospectrality of $H$ and $S$ in the case when $S$ is either symplectic or orthogonal of odd dimension.
Keywords:almost simple groups, orders of elements, recognition by spectrum.