Saturday, 20 September 2008

at.algebraic topology - Involutions of S2

are there some complete results on the involutions of 2 sphere?



at least I have three involutions:
(let mathbbZ2=1,g,and S2=(x,y,z)inmathbbR3|x2+y2+z2=1)



1.g(x,y,z)=(x,y,z)(antipodal map) with null fixed point set,and orbit space mathbbRP2
actully,for free involution on Sn with nleq3,the orbit space is homeomorphic to real projective space (Livesay 1960)



2.g(x,y,z)=(x,y,z) (rotation pi rad around z axis) with fixed point set S0(the north pole and south pole) and orbit space S2.



3.g(x,y,z)=(x,y,z)(reflection along z=0) with fixed point set S1 (the equator)and orbit space D2



i want to know if there are some other involutions over 2-sphere.
here we take two involutions as equivalent if there are conjugate in the homeomorphism group of S2

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