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Real Projective Space


Real projective space RP^n is the space of one-dimensional linear subspaces of R^(n+1). Equivalently, it is the quotient of the sphere S^n that identifies each point with its antipodal point. Its first two positive-dimensional examples are the real projective line, homeomorphic to a circle, and the real projective plane.

Small triangulations provide finite combinatorial models of these spaces. Guyer et al. (2026) constructed a 24-vertex triangulation of RP^5 and a 45-vertex triangulation of RP^6. Kolosov (2026) subsequently reported a 44-vertex triangulation of RP^6 with face vector

 (44,938,7024,22555,34936,25914,7404).

Its alternating sum is 1, as required by the Euler characteristic of RP^6. The construction is an antipodal quotient of the boundary of a centrally symmetric simplicial 7-polytope with 88 vertices. Exact verification programs were replayed by VibeMathed (2026). ChatGPT assisted the construction search and verification code, but independent expert review had not been reported as of Sep. 7, 2026. The construction supplies an upper bound of 44 vertices, not a proof of minimality.


See also

Antipodal Points, Euler Characteristic, Projective Space, Real Projective Plane, Triangulation

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References

Guyer, D.; Steinerberger, S.; and Yang, Y. "An Efficient Triangulation of RP^5." 8 Mar 2026. https://arxiv.org/abs/2603.07808.Kolosov, A. M. "A 44-Vertex Triangulation of Real Projective 6-Space." 2026. https://github.com/cheptil/44-vertex-triangulation.VibeMathed. "A 44-Vertex Triangulation of RP^6." 2026. https://vibemathed.com/problem/a-44-vertex-triangulation-of-mathbb-rp-6.

Cite this as:

Weisstein, Eric W. "Real Projective Space." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/RealProjectiveSpace.html

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