Sphere spectrum

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In stable homotopy theory, a branch of mathematics, the sphere spectrumS is the monoidal unit in the category of spectra. It is the suspension spectrum of S0, i.e., a set of two points. Explicitly, the nth space in the sphere spectrum is the n-dimensional sphere Sn, and the structure maps from the suspension of Sn to Sn+1 are the canonical homeomorphisms. The k-th homotopy group of a sphere spectrum is the k-th stable homotopy group of spheres.

The localization of the sphere spectrum at a prime number p is called the local sphere at p and is denoted by .

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