Mt845: Riemann Surfaces – from Analytic and Algebraic Viewpoints
نویسنده
چکیده
Example 1.2. (a) Suppose X is a Riemann surface. Let Y ⊂ X be a (connected) open subset. Then Y is a Riemann surface, whose complex structure is given by taking all U ⊂ Y from charts of X. (b) Let P = C ∪ {∞}, homeomorphic to the real sphere. Take U1 = P\{∞} = C, U2 = P\{0} = C∗ ∪ {∞}. Define φ1(z) = z, φ2(z) = 1/z for z 6= ∞ and φ2(∞) = 0. Then φ2 ◦ φ−1 1 : C∗ → C∗ is given by z 7→ 1/z, which is biholomorphic. Therefore, P is a Riemann surface, called the Riemann sphere or the projective line (over the field of complex numbers).
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