Plücker coordinates: Difference between revisions
→Rational points: Clarify some point about torsion |
→Height: Clarify lattice volume, add wikipedia links |
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We can define the height of a rational point simply as the Euclidean norm on its Plücker coordinates <math>X = \iota (P)</math>. | We can define the height of a rational point simply as the Euclidean norm on its Plücker coordinates <math>X = \iota (P)</math>. | ||
:<math> | :<math> | ||
H(P) = \left\| X \right\| = \left\| | H(P) = \left\| X \right\| = \left\| m_1 \wedge \ldots \wedge m_n \right\| \\ | ||
</math> | </math> | ||
In terms of the lattice defined by P, this definition is equivalent to the volume of the {{w|fundamental domain}}, also known as the lattice determinant. | |||
It is easy to show that this does not depend on the basis we choose. | |||
The height can be easily computed using the {{w|Gram matrix}}: | |||
:<math> | :<math> | ||
\begin{align} | \begin{align} | ||
\mathrm{G}_{ij} &= \left\langle | \mathrm{G}_{ij} &= \left\langle m_i, m_j \right\rangle \\ | ||
\sqrt{\det(\mathrm{G})} &= \left\| | \sqrt{\det(\mathrm{G})} &= \left\| m_1 \wedge \ldots \wedge m_n \right\| = \left\| X \right\| \, . | ||
\end{align} | \end{align} | ||
</math> | </math> |