A
-cell is a higher-dimensional version of a rectangle or
rectangular solid. It is the
Cartesian product
In mathematics, specifically set theory, the Cartesian product of two sets ''A'' and ''B'', denoted ''A''×''B'', is the set of all ordered pairs where ''a'' is in ''A'' and ''b'' is in ''B''. In terms of set-builder notation, that is
: A\ti ...
of
closed intervals on the
real line
In elementary mathematics, a number line is a picture of a graduated straight line (geometry), line that serves as visual representation of the real numbers. Every point of a number line is assumed to correspond to a real number, and every real ...
. This means that a
-dimensional rectangular solid has each of its edges equal to one of the closed intervals used in the definition. The
intervals need not be identical. For example, a 2-cell is a rectangle in
such that the sides of the rectangles are parallel to the coordinate axes. Every
-cell is
compact
Compact as used in politics may refer broadly to a pact or treaty; in more specific cases it may refer to:
* Interstate compact
* Blood compact, an ancient ritual of the Philippines
* Compact government, a type of colonial rule utilized in British ...
.
Formal definition
For every integer
from
to
, let
and
be
real numbers
In mathematics, a real number is a number that can be used to measure a ''continuous'' one-dimensional quantity such as a distance, duration or temperature. Here, ''continuous'' means that values can have arbitrarily small variations. Every real ...
such that for all
. The set of all points
in
whose coordinates satisfy the inequalities
is a
-cell.
Intuition
A
-cell of dimension
is especially simple. For example, a 1-cell is simply the interval