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The (logarithmic) Weil height of a nonzero rational number $a/b\in\mathbb{Q}$ in lowest terms is the quantity $$ h(a/b) = \log\max\bigl\{|a|,|b|\bigr\}. $$ The height of $0$ is taken to be $0.$

The (absolute logarithmic) Weil height of an element $\alpha$ in a number field $K$ is the quantity $$ h(\alpha) = \frac{1}{[K:\mathbb Q]} \sum_{v\in M_K} [K_v:\mathbb Q_v]\log\max\bigl\{\|\alpha\|_v,1\bigr\}, $$ where $M_K$ is an appropriately normalized set of inequivalent absolute values on $K$. More generally, the height of a point $P=[\alpha_0,\alpha_1,\ldots,\alpha_n]$ in projective space $\mathbb P^n(K)$ is given by $$ h(P) = \frac{1}{[K:\mathbb Q]} \sum_{v\in M_K} [K_v:\mathbb Q_v]\log\max_{0\le i\le n}\bigl\{\|\alpha_i\|_v\bigr\}. $$

Knowl status:
  • Review status: reviewed
  • Last edited by Alina Bucur on 2018-07-08 01:01:11
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