TY - CHAP

T1 - Central Projection of Quadrics and Möbius Geometry

AU - Bobenko, Alexander I.

AU - Lutz, Carl O.R.

AU - Pottmann, Helmut

AU - Techter, Jan

N1 - Publisher Copyright:
© 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.

PY - 2021

Y1 - 2021

N2 - In this section we study the general construction of central projection of a quadric from a point onto its polar hyperplane, see, e.g., [Kle1928, Bla1954, Gie1982]. This leads to a double cover of a Cayley-Klein space in the hyperplane such that the spheres in that Cayley-Klein space correspond to hyperplanar sections of the quadric. Vice versa, a Cayley-Klein space can be lifted to a quadric in a projective space of one dimension higher, such that Cayley-Klein spheres lift to hyperplanar sections of the quadric. In this way, hyperbolic and elliptic geometry can be lifted to Möbius geometry, and Möbius geometry may be seen as the geometry of points and spheres of the hyperbolic or elliptic space, respectively. We demonstrate how the group of Möbius transformations can be decomposed into the respective isometries and scalings along concentric spheres.

AB - In this section we study the general construction of central projection of a quadric from a point onto its polar hyperplane, see, e.g., [Kle1928, Bla1954, Gie1982]. This leads to a double cover of a Cayley-Klein space in the hyperplane such that the spheres in that Cayley-Klein space correspond to hyperplanar sections of the quadric. Vice versa, a Cayley-Klein space can be lifted to a quadric in a projective space of one dimension higher, such that Cayley-Klein spheres lift to hyperplanar sections of the quadric. In this way, hyperbolic and elliptic geometry can be lifted to Möbius geometry, and Möbius geometry may be seen as the geometry of points and spheres of the hyperbolic or elliptic space, respectively. We demonstrate how the group of Möbius transformations can be decomposed into the respective isometries and scalings along concentric spheres.

UR - http://www.scopus.com/inward/record.url?scp=85118568445&partnerID=8YFLogxK

U2 - 10.1007/978-3-030-81847-0_5

DO - 10.1007/978-3-030-81847-0_5

M3 - Chapter

AN - SCOPUS:85118568445

T3 - SpringerBriefs in Mathematics

SP - 37

EP - 56

BT - SpringerBriefs in Mathematics

PB - Springer Science and Business Media B.V.

ER -