Information About

3-sphere




In an entirely analogous manner one can define higher-dimensional spheres called Hypersphere s or ''n''-spheres. Such objects are ''n''-dimensional Manifold s.

Some people refer to a 3-sphere as a glome from the Latin word ''glomus'' meaning ''ball''. Roughly speaking, a glome is to a sphere as a sphere is to a circle.


DEFINITION


In Coordinates , a 3-sphere with center (''x''0, ''y''0, ''z''0, ''w''0) and radius ''r'' is the set of all points (''x'',''y'',''z'',w) in R4 such that
:( x - x_0 )^2 + ( y - y_0 )^2 + ( z - z_0 )^2 + ( w - w_0 )^2 = r^2. \,
The 3-sphere centered at the origin with radius 1 is called the unit 3-sphere and is usually denoted ''S''3. It can be described as a subset of either '''R'''4, '''C'''2, or '''H''' (the Quaternion s):

:S^3 = \left\{(x_1,x_2,x_3,x_4)\in\mathbb{R}^4\mid x_1^2 + x_2^2 + x_3^2 + x_4^2 = 1 ight\}

  :<math>S^3 \left\{q\in\mathbb{H}\mid q = 1 ight\}</math>
  { Class "wikitable"


  Where '''u''' (''u''<sub>1</sub>, ''u''<sub>2</sub>, ''u''<sub>3</sub>) is a vector in '''R'''<sup>3</sup> and ''u''<sup>2</sup> = ''u''<sub>1</sub><sup>2</sup> + ''u''<sub>2</sub><sup>2</sup> + ''u''<sub>3</sub><sup>2</sup> In the second equality above we have identified ''p'' with a unit quaternion and '''u''' = ''u''<sub>1</sub> ''i'' + ''u''<sub>2</sub> ''j'' + ''u''<sub>3</sub> ''k'' with a pure quaternion (Note that the division here is well-defined even though quaternionic multiplication is generally noncommutative) The inverse of this map takes ''p'' = (''x''<sub>0</sub>, ''x''<sub>1</sub>, ''x''<sub>2</sub>, ''x''<sub>3</sub>) in ''S''<sup>3</sup> to


  :<math>\mathbf{v} rac{1}{\u\^2}\mathbf{u}</math>