A simple root of a Lie algebra is a positive root that is not the sum of two positive roots.
Lie Algebra Simple Root
See also
Lie Algebra, Lie Algebra RootThis entry contributed by Shawn Westmoreland
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References
Jacobson, N. Lie Algebras. New York: Dover, p. 120, 1979.Referenced on Wolfram|Alpha
Lie Algebra Simple RootCite this as:
Weisstein, Eric W., with contributions by Shawn Westmoreland. "Lie Algebra Simple Root." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/LieAlgebraSimpleRoot.html