[幾何] degree-genus formul & branched cover
今天在教小朋友怎麼證 degree-genus formula of projective plane curves
g=(d-1)(d-2)/2
課本(Kirwan: complex algebraic curves)整個是土法煉鋼
euler number 全部用 triangulation 算, for any genus
Riemann-Hurwitz formula 用 lift of triangulation, 偏偏又要非常 precise
整個證了好多頁讓我好頭痛
偏偏小朋友們大多沒學過拓樸, 複變和微分幾何
所以對我亂切的 triangulation 和
從 branch cover curve -> P^1 lift triangulation 感到疑惑和不滿 @@,
我想問的是, 大家學 algebraic curves 的時候都把所有東西學過了才學嗎
然後把所有東西都證的好好的嗎 @@
還有如果我要說明 branched cover 在 ramification locus 地方長得像 z-> z^n
除了用複變以外, 可以用純拓樸的方法說為什麼嗎?
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