See: Four geometries, Geometry, Geometry theorems, Specifications
What distinguishes geometries?
- What are the geometries above and beyond the four basic geometries: affine, projective, conformal, symplectic?
- How are these other geometries distinguished?
- Systematize a list of geometries.
Kinds of geometry
From nLab overview:
- Euclidean geometry
- differential geometry of curves and surfaces
- Riemannian geometry
- G-structured differentiable manifolds (differential Cartan geometry)
- topos-theoretic notions (cf. “geometric logic”) of (higher) functorial geometry
- algebraic geometry
- supergeometry
- arithmetic geometry
- absolute geometry
- duality between algebra and geometry
- noncommutative geometry
- derived geometry
Incidence geometry
Euclidean space
- Euclidean geometry: empty space + tools: straightedge, compass, area measurer
- most important theorem: Pythagoras q=q1+q2
- (q1+q2+q3)2 = 2(q1^2 + q2^2 + q2^3)
- Euclidean space - (algebraic) coordinate systems - define left, right, front, backwards - and this often makes sense locally - but this does not make sense globally on a sphere, for example
Ordered geometry
- Features the concept of intermediacy. It is a common foundation for affine, Euclidean, absolute geometry and hyperbolic geometry, but not projective geometry. Like projective geometry, it omits the notion of measurement.
Absolute geometry
- Also known as neutral geometry, is based on the axioms of Euclidean geometry (including the first four of Euclid's axioms) but with the parallel postulate removed.
Thomas Lam. An invitation to positive geometries
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