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seen Dec 12 '13 at 10:54

Apr
5
awarded  Popular Question
Oct
29
accepted Monoids and groups of fractions
Oct
29
awarded  Scholar
Oct
29
asked Monoids and groups of fractions
Nov
13
comment The free group $F_2$ has index 12 in SL(2,$\mathbb{Z}$)
If someone is still interested in an explicit homomorphism: there is one in Example 2.5 of these notes by Keith Conrads: math.uconn.edu/~kconrad/blurbs/grouptheory/SL(2,Z).pdf
Apr
12
comment Rock-paper-scissors…
I guess "classification" is a soft term. For me, a classification is a one-to-one correspondence to a set of data together with a dictionary that allows you to just read off the answers to many interesting questions about the original objects, or at least answer them easily. In non-trivial cases, a classification will never enable you to answer all questions easily, so one has to specify "interesting questions". In this case "what is the number of instances of a given order?" should be one and if it's the only one, then classification in the sense above reduces to enumeration.
Apr
11
awarded  Editor
Apr
11
revised Rock-paper-scissors…
correction
Apr
11
awarded  Supporter
Apr
10
awarded  Nice Question
Apr
10
awarded  Student
Apr
10
asked Rock-paper-scissors…
Aug
29
answered Is this the CAT(0) metric on an affine building?
Jun
30
comment Properly Discontinuous Action
Of course, if a torsion-free group acts properly discontinuously, then it acts freely. So in that case the definitions are again equivalent.
Jun
30
answered Properly Discontinuous Action
Jun
22
awarded  Necromancer
Apr
16
awarded  Teacher
Apr
13
answered Fundamental Examples