Information About

Hypersphere




:\ R^2=\sum_{k=1}^n x_i^2.\,

The above hypersphere in \ n-dimensional Euclidean space is an example of an \ (n-1)- Manifold .
For example, an ordinary sphere in three dimensions is a 2-sphere, denoted by \mathbb{S}^2; the 1-sphere being a Circle , and the 0-sphere is the end points of an Interval .
Of course, translating the coordinates (i.e. moving the center around) doesn't change the analytic or geometric properties of the sphere.


HYPERSPHERICAL VOLUME

The hyperdimensional volume of the space which a (n-1)-sphere encloses (the n-ball) is:

:\ V_n={\pi^{n/2}R^n\over\Gamma(n/2+1)}

where Γ is the Gamma Function . (For even \ n , \ {\Gamma(n/2+1)= (n/2)!}.)

The "surface area" of this sphere is

:\ S_n= rac{dV_n}{dR}= rac{n V_n}{R}={2\pi^{n/2}R^{n-1}\over\Gamma(n/2)}

The interior of a hypersphere, that is the set of all points whose distance from the centre is less than \ R, is called a hyperball, or if the hypersphere itself is included, a closed hyperball.


HYPERSPHERICAL VOLUME - SOME EXAMPLES


For small values of \ n, the volumes, \ V_n , of the unit n-ball (\ R = 1 ) are:

If the dimension, \ n , is not limited to integral values, the hypersphere volume is a Continuous Function of \ n with a Global Maximum for the unit sphere in "dimension" ''n'' = 5.2569464... where the "volume" is 5.277768... Note that the hypercube circumscribed around the unit n-sphere has an edge length of 2 and hence a volume of 2''n''; the ratio of the volume of the hypersphere to its circumscribed hypercube decreases monotonically as the dimension increases.


HYPERSPHERICAL COORDINATES


We may define a coordinate system in an n-dimensional Euclidean space which is analogous
to the Spherical Coordinate System defined for 3-dimensional Euclidean space, in which
the coordinates consist of a radial coordinate \ r, and \ n-1 angular coordinates \ \phi _1 , \phi _2 , ... , \phi _{n-1}. If \ x_i are the
Cartesian coordinates, then we may define

:x_1=r\cos(\phi_1)\,
:x_2=r\sin(\phi_1)\cos(\phi_2)\,
:x_3=r\sin(\phi_1)\sin(\phi_2)\cos(\phi_3)\,
:\cdots\,
:x_{n-1}=r\sin(\phi_1)\cdots\sin(\phi_{n-2})\cos(\phi_{n-1})\,
:x_n~~\,=r\sin(\phi_1)\cdots\sin(\phi_{n-2})\sin(\phi_{n-1})\,

The hyperspherical volume element will be found from the Jacobian of the transformation:

:d^nr =


SEE ALSO