## On Quadrics and Pseudoquadrics Inversions in Hyperpseudospheres

**Authors:** Robert B. Easter

This note on quadrics and pseudoquadrics inversions in hyperpseudospheres shows that the inversions produce different results in a three-dimensional spacetime. Using Geometric Algebra, all quadric and pseudoquadric entities and operations are in the G(4,8) Double Conformal Space-Time Algebra (DCSTA). Quadrics at zero velocity are purely spatial entities in x y z-space that are hypercylinders in w x y z-spacetime. Pseudoquadrics represent quadrics in a three-dimensional (3D) x y w, y z w, or z x w spacetime with the pseudospatial w-axis that is associated with time w=c t. The inversion of a quadric in a hyperpseudosphere can produce a Darboux pseudocyclide in a 3D spacetime that is a quartic hyperbolic (infinite) surface, which does not include the point at infinity. The inversion of a pseudoquadric in a hyperpseudosphere can produce a Darboux pseudocyclide in a 3D spacetime that is a quartic finite surface. A quadric and pseudoquadric can represent the same quadric surface in space, and their two different inversions in a hyperpseudosphere represent the two types of reflections of the quadric surface in a hyperboloid.

**Comments:** 4 Pages.

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### Submission history

[v1] 2016-08-09 15:55:41

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