In mathematics, specifically in
order theory
Order theory is a branch of mathematics that investigates the intuitive notion of order using binary relations. It provides a formal framework for describing statements such as "this is less than that" or "this precedes that". This article int ...
, a
binary relation on a
vector space
In mathematics and physics, a vector space (also called a linear space) is a set whose elements, often called '' vectors'', may be added together and multiplied ("scaled") by numbers called ''scalars''. Scalars are often real numbers, but can ...
over the
real
Real may refer to:
Currencies
* Brazilian real (R$)
* Central American Republic real
* Mexican real
* Portuguese real
* Spanish real
* Spanish colonial real
Music Albums
* ''Real'' (L'Arc-en-Ciel album) (2000)
* ''Real'' (Bright album) (2010) ...
or
complex number
In mathematics, a complex number is an element of a number system that extends the real numbers with a specific element denoted , called the imaginary unit and satisfying the equation i^= -1; every complex number can be expressed in the fo ...
s is called Archimedean if for all
whenever there exists some
such that
for all positive integers
then necessarily
An Archimedean (pre)ordered vector space is a (pre)
ordered vector space
In mathematics, an ordered vector space or partially ordered vector space is a vector space equipped with a partial order that is compatible with the vector space operations.
Definition
Given a vector space ''X'' over the real numbers R and a pr ...
whose order is Archimedean.
A pre
ordered vector space
In mathematics, an ordered vector space or partially ordered vector space is a vector space equipped with a partial order that is compatible with the vector space operations.
Definition
Given a vector space ''X'' over the real numbers R and a pr ...
is called almost Archimedean if for all
whenever there exists a
such that
for all positive integers
then
Characterizations
A pre
ordered vector space
In mathematics, an ordered vector space or partially ordered vector space is a vector space equipped with a partial order that is compatible with the vector space operations.
Definition
Given a vector space ''X'' over the real numbers R and a pr ...
with an
order unit is Archimedean preordered if and only if
for all non-negative integers
implies
Properties
Let
be an
ordered vector space
In mathematics, an ordered vector space or partially ordered vector space is a vector space equipped with a partial order that is compatible with the vector space operations.
Definition
Given a vector space ''X'' over the real numbers R and a pr ...
over the reals that is finite-dimensional. Then the order of
is Archimedean if and only if the positive cone of
is closed for the unique topology under which
is a Hausdorff TVS.
Order unit norm
Suppose
is an ordered vector space over the reals with an
order unit whose order is Archimedean and let
Then the
Minkowski functional of
(defined by
) is a norm called the order unit norm.
It satisfies
and the closed unit ball determined by
is equal to