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Mathlib.Topology.Category.TopCat.Sphere

Euclidean spheres #

This file defines the n-sphere 𝕊 n, the n-disk 𝔻 n, its boundary ∂𝔻 n and its interior 𝔹 n as objects in TopCat.

noncomputable def TopCat.disk (n : ) :

The n-disk is the set of points in ℝⁿ whose norm is at most 1, endowed with the subspace topology.

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      noncomputable def TopCat.diskBoundary (n : ) :

      The boundary of the n-disk.

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          noncomputable def TopCat.sphere (n : ) :

          The n-sphere is the set of points in ℝⁿ⁺¹ whose norm equals 1, endowed with the subspace topology.

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              noncomputable def TopCat.ball (n : ) :

              The n-ball is the set of points in ℝⁿ whose norm is strictly less than 1, endowed with the subspace topology.

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                  𝔻 n denotes the n-disk.

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                      ∂𝔻 n denotes the boundary of the n-disk.

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                          𝕊 n denotes the n-sphere.

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                              𝔹 n denotes the n-ball, the interior of the n-disk.

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                                  The inclusion ∂𝔻 n ⟶ 𝔻 n of the boundary of the n-disk.

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                                      The inclusion 𝔹 n ⟶ 𝔻 n of the interior of the n-disk.

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