Almost recognition by spectrum for specified simple classical groups

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For a finite group GG, write ω(G)\omega(G) for its spectrum, the set of orders of its elements. Two finite groups are isospectral if their spectra coincide. A finite group is almost simple if it contains a nonabelian simple group between its socle and its automorphism group.

Vasil'ev–Grechkoseeva conjecture. Suppose that LL is one of the following nonabelian simple groups:

Ln(q),n⩾5;Un(q),n⩾5 and (n,q)≠(5,2);S2n(q),n⩾3, n≠4 and (n,q)≠(3,2);O2n+1(q),q odd, n⩾3, n≠4 and (n,q)≠(3,3);O2nε(q),n⩾4 and (n,q,ε)≠(4,2,+),(4,3,+).\begin{array}{ll} L_n(q), & n\geqslant5;\\ U_n(q), & n\geqslant5\text{ and }(n,q)\neq(5,2);\\ S_{2n}(q), & n\geqslant3,\ n\neq4\text{ and }(n,q)\neq(3,2);\\ O_{2n+1}(q), & q\text{ odd},\ n\geqslant3,\ n\neq4\text{ and }(n,q)\neq(3,3);\\ O_{2n}^{\varepsilon}(q), & n\geqslant4\text{ and }(n,q,\varepsilon)\neq(4,2,+),(4,3,+). \end{array}

Then every finite group isospectral to LL is an almost simple group with socle isomorphic to LL.

The claim is presented as a conjectural sharpening after the general Mazurov conjecture was proved. The supplied source does not establish a resolution of this specific statement.

References

Primary source

M. A. Grechkoseeva, A. V. Vasil'ev and M. A. Zvezdina, “On recognition of symplectic and orthogonal groups of small dimensions by spectrum”, arXiv:1806.07045 (2018).

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