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Let $k$ be the largest positive integer such that $p^k \mid |G|$ and let $|H|=p^i$ where $0<i < k$. What should I prove to say that $H \subset H_1$ where $|H_1|=p^{i+1}$, and what guarantees the existence of $H_1$?

user10444
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1 Answers1

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Some hints from J.D.Dixon. I found them for you:

  • Write the order of $G$ as $|G|=|Px_1H|+|Px_2H|+...+|Px_sH|$ for some elements $x_i\in G$.
  • If $|P|=p^r$ then $p^{r+1}$ does not divide $|G|$.
  • So there is some double coset $PxH$ that $p^{r+1}$ does not divide its order.
  • Use the point that $|PxH|=\frac{|P|}{[H:x^{-1}Px\cap H]}$
  • $H$ is a $p-$ group.
Mikasa
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  • This is a bit too advanced for me, as I have never worked with double cosets. I'll try to read about them on Wikipedia and get back to these hints. Thank you – user10444 Apr 13 '13 at 19:36
  • Great hints, Babak. Good reference! – amWhy Apr 14 '13 at 01:19
  • How are you?;-) I hope you slept blissfully! I will likely head to bed soon (almost midnight for me!) – amWhy Apr 14 '13 at 04:57
  • @amWhy: So hurry. there is a warm and charming bed prepared for you. I slept well, and I hop you will have the same full of stars. ;-) – Mikasa Apr 14 '13 at 05:03
  • I miss you!! ;-) – amWhy Apr 15 '13 at 02:58
  • @amWhy: My tel line has not been implemented yet. I miss being in the site, with you, with others, doing Maths and.... – Mikasa Apr 15 '13 at 07:54