Homotopy groups of spheres
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In the mathematical field of algebraic topology, the homotopy groups of spheres describe how spheres of various dimensions can wrap around each other. They are examples of topological invariants, whic
A homotopy from a circle around a sphere down to a single point
Riemann sphere
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In mathematics, the Riemann sphere, named after Bernhard Riemann, is a model of the extended complex plane : the complex plane plus one point at infinity. This extended plane represents the extended c
Riemann sphere: almost the whole earth in stereographic azimuthal projection 1:500.000.000 (254 dpi)