If is a root system, with an Euclidean vector space, then a subset is called a set of positive roots if there is a vector such that if , and if . http://planetmath.org/node/3645Roots which are not positive are called negative. Since is negative if and only if is positive, exactly half the must be positive.
|Date of creation||2013-03-22 13:11:46|
|Last modified on||2013-03-22 13:11:46|
|Last modified by||mathwizard (128)|