Almost recognition by spectrum for specified simple classical groups

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),n5;Un(q),n5 and (n,q)(5,2);S2n(q),n3, n4 and (n,q)(3,2);O2n+1(q),q odd, n3, n4 and (n,q)(3,3);O2nε(q),n4 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.

Sources & referencesView supporting material

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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