Bounds for the Index of the Centre in Capable Groups
نویسندگان
چکیده
A group H is called capable if it is isomorphic to G/Z(G) for some group G. Let H be a capable group. I. M. Isaacs (2001) showed that if H is finite, then the index of the centre is bounded above by some function of |H′|. We show that if |H′| < ∞, then |H : Z(H)| ≤ |H′|c log2 |H′| with some constant c and this bound is essentially best possible. We complete a result of Isaacs, showing that if H′ is a cyclic group, then |H : Z(H)| ≤ |H′|2.
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تاریخ انتشار 2005