Parabolic Lie algebra

In algebra, a parabolic Lie algebra $\mathfrak p$ is a subalgebra of a semisimple Lie algebra ${\mathfrak {g}}$ satisfying one of the following two conditions:

• $\mathfrak p$ contains a maximal solvable subalgebra (a Borel subalgebra) of ${\mathfrak {g}}$;
• the Killing perp of $\mathfrak p$ in ${\mathfrak {g}}$ is the nilradical of $\mathfrak p$.

These conditions are equivalent over an algebraically closed field of characteristic zero, such as the complex numbers. If the field $\mathbb F$ is not algebraically closed, then the first condition is replaced by the assumption that

• ${\displaystyle {\mathfrak {p}}\otimes _{\mathbb {F} }{\overline {\mathbb {F} }}}$ contains a Borel subalgebra of ${\displaystyle {\mathfrak {g}}\otimes _{\mathbb {F} }{\overline {\mathbb {F} }}}$

where ${\displaystyle {\overline {\mathbb {F} }}}$ is the algebraic closure of $\mathbb F$.

See also

• Generalized flag variety

Bibliography

• Baston, Robert J.; Eastwood, Michael G. (1989), The Penrose Transform: its Interaction with Representation Theory, Oxford University Press.
• Fulton, William; Harris, Joe (1991). Representation theory. A first course. Graduate Texts in Mathematics, Readings in Mathematics. 129. New York: Springer-Verlag. ISBN 978-0-387-97495-8. MR 1153249, ISBN 978-0-387-97527-6.
• Grothendieck, Alexander (1957), "Sur la classification des fibrés holomorphes sur la sphère de Riemann", Amer. J. Math., 79 (1): 121–138, doi:10.2307/2372388, JSTOR 2372388.
• Humphreys, J. (1972), Linear Algebraic Groups, New York: Springer, ISBN 0-387-90108-6