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Subgroup of all elements of prime order and its ordinal, under some conditions

Source: Romania National Olympiad 2014, Grade XII, Problem 4

March 3, 2019
number theoryprime numbersgroup theoryabstract algebra

Problem Statement

Let be a finite group G G that has an element a1 a\neq 1 for which exists a prime number p p such that x1+p=a1xa, x^{1+p}=a^{-1}xa, for all xG. x\in G.
a) Prove that the order of G G is a power of p. p. b) Show that H:={xGord(x)=p}G H:=\{x\in G|\text{ord} (x)=p\}\le G and ord2(H)>ord(G). \text{ord}^2(H)>\text{ord}(G).