Geodesic
On element orders in covers of $L_4(q)$ and $U_4(q)$
Sibirskie èlektronnye matematičeskie izvestiâ, Tome 17 (2020), pp. 585-589.

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Suppose that $L$ is one of the finite simple groups $\operatorname{PSL}_4(q)$ or $\operatorname{PSU}_4(q)$ and $L$ acts on a vector space $W$ over a field whose characteristic divides $q$. We prove that the natural semidirect product of $W$ and $L$ contains an element whose order differs from the order of any element of $L$, thus answering questions 14.60 and 17.73 (a) of the Kourovka Notebook.
Keywords: simple linear group, simple unitary group, orders of elements, modular representation, defining characteristic. 
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M. A. Grechkoseeva; S. V. Skresanov. On element orders in covers of $L_4(q)$ and $U_4(q)$. Sibirskie èlektronnye matematičeskie izvestiâ, Tome 17 (2020), pp. 585-589. http://geodesic.mathdoc.fr/item/SEMR_2020_17_a9/

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