Bubboloni–Praeger–Spiga conjecture for the normal covering number of alternating groups

Let n=p1α1prαrn=p_1^{\alpha_1}\cdots p_r^{\alpha_r}, where r2r\geq2, the pip_i are primes, αiN\alpha_i\in\mathbb{N}, and pi<pjp_i<p_j for i<ji<j. Define

g(n):=n2(11p1)(11p2)+2.g(n):=\frac{n}{2}\left(1-\frac{1}{p_1}\right)\left(1-\frac{1}{p_2}\right)+2.

Assume that nn is even, r2r\geq2, and n2p2,12n\neq2p_2,12.

Normal covering conjecture for AnA_n.

γ(An)=g(n).\gamma(A_n)=g(n).

This is the alternating-group counterpart of the proposed formula for γ(Sn)\gamma(S_n). The paper establishes linear growth and discusses evidence for the formula, but the exact value remains open in the stated generality.

Sources & referencesView supporting material

Primary source

Daniela Bubboloni, Cheryl E. Praeger and Pablo Spiga, “Conjectures on the normal covering number of the finite symmetric and alternating groups”, arXiv:1310.2911 (2013).

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