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 Feb 14 revised Conformal mapping from square to disk as inverse of hypergeometric function added 13 characters in body Feb 11 answered Conformal mapping from square to disk as inverse of hypergeometric function Oct 21 comment Topology of SL(2,R) It isn't a complex curve - the equality $|a|^2 - |b|^2 = 1$ is one real condition, not one complex condition. So you expect the group to be three real-dimensional. By the way, you are very close to having a direct answer using the first description you gave. Try to show that $X^2 - z^2 - w^2 = 1$ describes a copy of $\mathbb{R}^2$. Sep 17 comment Seeking a good book or site describing the 3-sphere Very nice pictures! Sep 17 comment Algebraic Topology Question Regarding a Space @ Sen - Just a quick remark. Prof Brown's remarks are not a proof but rather a sequence of hints. We would have to provide the claimed homeomorphisms with $A$ and with $B$, and check that the induced gluing of $\partial A$ to $\partial B$ agrees with $f$. But these are exercises "left to the reader". :) Aug 21 comment flat manifold, curvature and the circle You are confusing two notions of curvature. There is the geodesic curvature of a circle (which depends on its embedding in the plane) and the Riemannian curvature of the circle (which is intrinsic). Aug 21 answered Question of maps in Mayer-Vietoris sequence Aug 18 awarded Yearling Jul 15 revised Figure eight knot is not a torus knot typo Jun 20 revised Orientable Surface Covers Non-Orientable Surface added 4 characters in body Jun 20 answered Orientable Surface Covers Non-Orientable Surface Jun 9 revised Embedding covers of manifolds added adjective Jun 9 revised Embedding covers of manifolds added closed examples. Jun 9 answered Embedding covers of manifolds Feb 14 reviewed Approve Periodic Function With A Given Functional Equation Feb 14 revised Mapping Class Group fixed typo Jan 26 reviewed Reject Square root of complex number in polar or rectangular form Jan 26 comment Evaluate the sum $x + \frac{x^3}{3} + \frac{x^5}{5} + …$ What do you get if you set $x = 0$? This kind of checking of special values is useful for quickly detecting mistakes. Jan 26 answered Why is SO(3) not $S^1 \times S^2$? (Where is the mistake?) Jan 11 reviewed Approve Find values of $a$ for which $\sum\limits_{n=1}^\infty n^{-a}\log ( 1 + n^{-1})$ converges