Conics in the hyperbolic plane intrinsic to the collineation group (Q1928600)
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scientific article; zbMATH DE number 6121637
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | Conics in the hyperbolic plane intrinsic to the collineation group |
scientific article; zbMATH DE number 6121637 |
Statements
Conics in the hyperbolic plane intrinsic to the collineation group (English)
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3 January 2013
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Let \((\mathcal P,\mathcal L)\) be any planar point-line geometry and \(\Gamma\) its group of collineations. Assume \(P\in{\mathcal P}\), \(T\in\Gamma\), \(T(P)\not=P\), \(P\vee\,T(P)=:G\), and \(T(G)\not=G\), then the locus of intersections \(\{L\cap\,T(L)\,|\,L\in{\mathcal L}, P\in\,L\}\) is called an \textit{intrinsic conic} of \((\mathcal P,\mathcal L)\). This definition is independent of any embedding of \((\mathcal P,\mathcal L)\) into a larger geometry. The author classifies the intrinsic conics of the plane real hyperbolic geometry \(H\) using the conformal Poincaré disk and complex numbers. There exist seven classes of intrinsic conics in \(H\), for each class the author exhibits a representative. Clearly, each intrinsic conic is a projective conic, yet there are four categories of projective conics which are not intrinsic conics. The computations and considerations are accompanied by 5 illustrative figures.
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plane hyperbolic geometry
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intrinsic conic
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focus
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focal axis
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directrix
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conformal Poincaré disk
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split inversion
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