Wikipedia:Reference desk/Archives/Mathematics/2013 June 22
| Mathematics desk | ||
|---|---|---|
| < June 21 | << May | June | Jul >> | June 23 > |
| Welcome to the Wikipedia Mathematics Reference Desk Archives |
|---|
| The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
June 22[edit]
double coset question[edit]
Given a group G and a subgroup H , and a mapping from G/H into H/G\H defined by f(aH) = HaH for all a in G, f is a bijection if and only if H is normal in G. Remag12 (talk) 22:41, 22 June 2013 (UTC)
- One direction is obvious. For the other show that every left coset is a right coset. Sławomir Biały (talk) 23:54, 22 June 2013 (UTC).It is easier to show if H is not normal in G, then f is not an injection.