projective envelope
1Projective cover — In category theory, a projective cover of an object X is in a sense the best approximation of X by a projective object P . Projective covers are the dual of injective envelopes. Definition Let mathcal{C} be a category and X an object in… …
2Motive (algebraic geometry) — For other uses, see Motive (disambiguation). In algebraic geometry, a motive (or sometimes motif, following French usage) denotes some essential part of an algebraic variety . To date, pure motives have been defined, while conjectural mixed… …
3Lie sphere geometry — is a geometrical theory of planar or spatial geometry in which the fundamental concept is the circle or sphere. It was introduced by Sophus Lie in the nineteenth century. [The definitive modern textbook on Lie sphere geometry is Harvnb|Cecil|1992 …
4Affine geometry — is a form of geometry featuring the unique parallel line property (see the parallel postulate) but where the notion of angle is undefined and lengths cannot be compared in different directions (that is, Euclid s third and fourth postulates are… …
5Ellipse — Elliptical redirects here. For the exercise machine, see Elliptical trainer. This article is about the geometric figure. For other uses, see Ellipse (disambiguation). Not to be confused with ellipsis. An ellipse obtained as the intersection of a… …
6Monge cone — In the mathematical theory of partial differential equations (PDE), the Monge cone is a geometrical object associated with a first order equation. It is named for Gaspard Monge. In two dimensions, let be a PDE for an unknown real valued function… …
7Injective cogenerator — In category theory, the concept of an injective cogenerator is drawn from examples such as Pontryagin duality. Generators are objects which cover other objects as an approximation, and (dually) cogenerators are objects which envelope other… …
8List of differential geometry topics — This is a list of differential geometry topics. See also glossary of differential and metric geometry and list of Lie group topics. Contents 1 Differential geometry of curves and surfaces 1.1 Differential geometry of curves 1.2 Differential… …
9Line coordinates — In geometry, line coordinates are used to specify the position of a line just as point coordinates (or simply coordinates) are used to specify the position of a point. Contents 1 Lines in the plane 2 Tangential equations 3 Tangential equation of… …
10Differential geometry of surfaces — Carl Friedrich Gauss in 1828 In mathematics, the differential geometry of surfaces deals with smooth surfaces with various additional structures, most often, a Riemannian metric. Surfaces have been extensively studied from various perspectives:… …
