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Questions tagged [projective-geometry]

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9
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1answer
122 views

What theorem of Sophus Lie on the number of geometries is H. Poincaré referring to?

In this quotation from Henri Poincaré's essay "Non-Euclidean Geometry" published in Nature in 1892 (No. 1165, Vol 45, p. 406), he refers to a theorem of Sophus Lie. Does anyone know a source for this ...
5
votes
1answer
59 views

What was the old system of using right circular cones to solve problems about circles in the plane?

[I asked this originally at the Math Stack Exchange, and they suggested I also ask about it here.] I heard about this from a college professor but haven't ever been able to find any other mention of ...
3
votes
1answer
139 views

Did Einstein get inspired by projective geometry?

I read somewhere that projective geometry was an inspiration to Einstein to build the theory of relativity. However, the keyword "projective geometry" isn't mentioned in history of general relativity ...
10
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2answers
387 views

Where was the word “pencil” first used in (projective) geometry and what is the reason behind this curious name?

The title is pretty self-explanatory: A pencil in projective (or algebraic) geometry is the family of all lines through a point. The above-linked website tells me that Cremona, on page x of Elements ...