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  2. 3-sphere - Wikipedia

    en.wikipedia.org/wiki/3-sphere

    Direct projection of 3-sphere into 3D space and covered with surface grid, showing structure as stack of 3D spheres (2-spheres) In mathematics, a hypersphere or 3-sphere is a 4-dimensional analogue of a sphere, and is the 3-dimensional n-sphere. In 4-dimensional Euclidean space, it is the set of points equidistant from a fixed central point.

  3. Sphere packing - Wikipedia

    en.wikipedia.org/wiki/Sphere_packing

    The sphere packing problem is the three-dimensional version of a class of ball-packing problems in arbitrary dimensions. In two dimensions, the equivalent problem is packing circles on a plane. In one dimension it is packing line segments into a linear universe. [10]

  4. Point groups in three dimensions - Wikipedia

    en.wikipedia.org/wiki/Point_groups_in_three...

    When comparing the symmetry type of two objects, the origin is chosen for each separately, i.e., they need not have the same center. Moreover, two objects are considered to be of the same symmetry type if their symmetry groups are conjugate subgroups of O(3) (two subgroups H 1, H 2 of a group G are conjugate, if there exists g ∈ G such that H 1 = g −1 H 2 g).

  5. Sphere - Wikipedia

    en.wikipedia.org/wiki/Sphere

    S ‍ 1: a 1-sphere is a circle of radius r; S ‍ 2: a 2-sphere is an ordinary sphere; S ‍ 3: a 3-sphere is a sphere in 4-dimensional Euclidean space. Spheres for n > 2 are sometimes called hyperspheres. The n-sphere of unit radius centered at the origin is denoted S ‍ n and is often referred to as "the" n-sphere. The ordinary sphere is a ...

  6. n-sphere - Wikipedia

    en.wikipedia.org/wiki/N-sphere

    In mathematics, an n-sphere or hypersphere is an ⁠ ⁠-dimensional generalization of the ⁠ ⁠-dimensional circle and ⁠ ⁠-dimensional sphere to any non-negative integer ⁠ ⁠. The circle is considered 1-dimensional, and the sphere 2-dimensional, because the surfaces themselves are 1- and 2-dimensional respectively, not because they ...

  7. Solid geometry - Wikipedia

    en.wikipedia.org/wiki/Solid_geometry

    A solid figure is the region of 3D space bounded by a two-dimensional closed surface; for example, a solid ball consists of a sphere and its interior. Solid geometry deals with the measurements of volumes of various solids, including pyramids , prisms (and other polyhedrons ), cubes , cylinders , cones (and truncated cones ).

  8. Kepler conjecture - Wikipedia

    en.wikipedia.org/wiki/Kepler_conjecture

    The Kepler conjecture, named after the 17th-century mathematician and astronomer Johannes Kepler, is a mathematical theorem about sphere packing in three-dimensional Euclidean space. It states that no arrangement of equally sized spheres filling space has a greater average density than that of the cubic close packing ( face-centered cubic ) and ...

  9. 3-manifold - Wikipedia

    en.wikipedia.org/wiki/3-manifold

    A 3-torus in this sense is an example of a 3-dimensional compact manifold. It is also an example of a compact abelian Lie group. This follows from the fact that the unit circle is a compact abelian Lie group (when identified with the unit complex numbers with multiplication). Group multiplication on the torus is then defined by coordinate-wise ...