QUASIRECOGNIZABILITY OF SIMPLE UNITARY GROUPS OVER FIELDS OF EVEN ORDER
We refer to the set of element orders of a finite group as the spectrum of this group and say that two groups are isospectral if their spectra coincide. We prove that finite simple unitary groups of dimension at least 5 over fields of characteristic 2 other than U5(2) are quasirecognizable by spectrum, that is every finite group isospectral to such unitary group U has a unique nonabelian composition factor and this factor is isomorphic to U.