LieAlgebras[GradeSemiSimpleLieAlgebra] - find the grading of a semi-simple Lie algebra defined by a set of simple roots or restricted simple roots
Calling Sequences
GradeSemiSimpleLieAlgebra( 1)
GradeSemiSimpleLieAlgebra( 2, method = "non-compact")
Parameters
Sigma - a list or set of column vectors, defining a subset of the simple roots or a subset of the restricted simple roots
T1 - a table, with indices that include "RootSpaceDecomposition", "CartanSubalgebra", "SimpleRoots", "PositiveRoots"
T2 - a table, with indices that include "RestrictedRoot SpaceDecomposition", "CartanSubalgebraDecomposition", "RestrictedSimpleRoots", "RestrictedPositiveRoots"
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Description
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 and   ![`𝔤`[0] = `𝔥` (⨁)[alpha[] : ht[Sigma](alpha[]) =0] R[alpha[]]](/support/helpjp/helpview.aspx?si=6614/file05805/math96.png)
define a (symmetric) grading g = ![(⨁)^()[t = -k ]^(k) `𝔤`[t].](/support/helpjp/helpview.aspx?si=6614/file05805/math100.png)
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The command Query/"Gradation" will test if a given decomposition of a Lie algebra is graded.
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Examples
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Example 1.
We calculate the various gradations for We use the command SimpleLieAlgebraData to initialize the Lie algebra.
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![LD := SimpleLieAlgebraData("sl(4)", sl4, labelformat = "gl", labels = [E, omega])](/support/helpjp/helpview.aspx?si=6614/file05805/math144.png)
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| (2.1) |
sl4 >
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We use the command SimpleLieAlgebraProperties to create a table containing the structure properties of .
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sl4 >
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![SR := T["SimpleRoots"]](/support/helpjp/helpview.aspx?si=6614/file05805/math180.png)
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![SR := [Vector(3, {(1) = 1, (2) = -1, (3) = 0}), Vector(3, {(1) = 0, (2) = 1, (3) = -1}), Vector(3, {(1) = 1, (2) = 1, (3) = 2})]](/support/helpjp/helpview.aspx?si=6614/file05805/math183.png)
| (2.2) |
Here are the possible subsets of the set of simple roots.
sl4 >
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![Sigma := [[], SR[1 .. 1], SR[2 .. 2], SR[3 .. 3], SR[1 .. 2], SR[2 .. 3], [SR[1], SR[3]], SR]](/support/helpjp/helpview.aspx?si=6614/file05805/math197.png)
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| (2.3) |
Here are the gradings defined by each subset of the simple roots.
sl4 >
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![Sigma[1], GradeSemiSimpleLieAlgebra(Sigma[1], P)](/support/helpjp/helpview.aspx?si=6614/file05805/math214.png)
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| (2.4) |
sl4 >
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![Sigma[2], GradeSemiSimpleLieAlgebra(Sigma[2], P)](/support/helpjp/helpview.aspx?si=6614/file05805/math221.png)
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![[Vector(3, {(1) = 1, (2) = -1, (3) = 0})], table([0 = [E11, E22, E33, E23, E34, E24, E32, E43, E42], 1 = [E12, E13, E14], -1 = [E21, E31, E41]])](/support/helpjp/helpview.aspx?si=6614/file05805/math224.png)
| (2.5) |
sl4 >
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![Sigma[3], GradeSemiSimpleLieAlgebra(Sigma[3], P)](/support/helpjp/helpview.aspx?si=6614/file05805/math228.png)
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![[Vector(3, {(1) = 0, (2) = 1, (3) = -1})], table([0 = [E11, E22, E33, E12, E34, E21, E43], 1 = [E23, E13, E24, E14], -1 = [E32, E31, E42, E41]])](/support/helpjp/helpview.aspx?si=6614/file05805/math231.png)
| (2.6) |
sl4 >
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![Sigma[4], GradeSemiSimpleLieAlgebra(Sigma[4], P)](/support/helpjp/helpview.aspx?si=6614/file05805/math235.png)
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![[Vector(3, {(1) = 1, (2) = 1, (3) = 2})], table([0 = [E11, E22, E33, E12, E23, E13, E21, E32, E31], 1 = [E34, E24, E14], -1 = [E43, E42, E41]])](/support/helpjp/helpview.aspx?si=6614/file05805/math238.png)
| (2.7) |
sl4 >
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![Sigma[5], GradeSemiSimpleLieAlgebra(Sigma[5], P)](/support/helpjp/helpview.aspx?si=6614/file05805/math242.png)
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![[Vector(3, {(1) = 1, (2) = -1, (3) = 0}), Vector(3, {(1) = 0, (2) = 1, (3) = -1})], table([0 = [E11, E22, E33, E34, E43], 1 = [E12, E23, E24], 2 = [E13, E14], -2 = [E31, E41], -1 = [E21, E32, E42]])](/support/helpjp/helpview.aspx?si=6614/file05805/math245.png)
| (2.8) |
sl4 >
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![Sigma[6], GradeSemiSimpleLieAlgebra(Sigma[6], P)](/support/helpjp/helpview.aspx?si=6614/file05805/math249.png)
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![[Vector(3, {(1) = 0, (2) = 1, (3) = -1}), Vector(3, {(1) = 1, (2) = 1, (3) = 2})], table([0 = [E11, E22, E33, E12, E21], 1 = [E23, E34, E13], 2 = [E24, E14], -2 = [E42, E41], -1 = [E32, E43, E31]])](/support/helpjp/helpview.aspx?si=6614/file05805/math252.png)
| (2.9) |
sl4 >
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![Sigma[7], GradeSemiSimpleLieAlgebra(Sigma[7], P)](/support/helpjp/helpview.aspx?si=6614/file05805/math256.png)
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![[Vector(3, {(1) = 1, (2) = -1, (3) = 0}), Vector(3, {(1) = 1, (2) = 1, (3) = 2})], table([0 = [E11, E22, E33, E23, E32], 1 = [E12, E34, E13, E24], 2 = [E14], -2 = [E41], -1 = [E21, E43, E31, E42]])](/support/helpjp/helpview.aspx?si=6614/file05805/math259.png)
| (2.10) |
sl4 >
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![Sigma[8], GradeSemiSimpleLieAlgebra(Sigma[8], P)](/support/helpjp/helpview.aspx?si=6614/file05805/math263.png)
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![[Vector(3, {(1) = 1, (2) = -1, (3) = 0}), Vector(3, {(1) = 0, (2) = 1, (3) = -1}), Vector(3, {(1) = 1, (2) = 1, (3) = 2})], table([0 = [E11, E22, E33], 1 = [E12, E23, E34], 2 = [E13, E24], 3 = [E14], -3 = [E41], -2 = [E31, E42], -1 = [E21, E32, E43]])](/support/helpjp/helpview.aspx?si=6614/file05805/math266.png)
| (2.11) |
sl4 >
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![Sigma[2], GradeSemiSimpleLieAlgebra(Sigma[2], P)](/support/helpjp/helpview.aspx?si=6614/file05805/math270.png)
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![[Vector(3, {(1) = 1, (2) = -1, (3) = 0})], table([0 = [E11, E22, E33, E23, E34, E24, E32, E43, E42], 1 = [E12, E13, E14], -1 = [E21, E31, E41]])](/support/helpjp/helpview.aspx?si=6614/file05805/math273.png)
| (2.12) |
The Query command can be used to check that each of these define a grading of .
sl4 >
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![G7 := GradeSemiSimpleLieAlgebra(Sigma[7], P)](/support/helpjp/helpview.aspx?si=6614/file05805/math295.png)
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| (2.13) |
sl4 >
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| (2.14) |
Example 2.
We calculate the various gradings for We use the command SimpleLieAlgebraData to initialize the Lie algebra.
sl4 >
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![LD2 := SimpleLieAlgebraData("so(5,3)", so53, labelformat = "gl", labels = [R, theta])](/support/helpjp/helpview.aspx?si=6614/file05805/math329.png)
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sl4 >
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We use the command SimpleLieAlgebraProperties to calculate the restricted root space decomposition, restricted simple roots, etc.
so53 >
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so53 >
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![RSR := T["RestrictedSimpleRoots"]](/support/helpjp/helpview.aspx?si=6614/file05805/math359.png)
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![RSR := [Vector(3, {(1) = 1, (2) = -1, (3) = 0}), Vector(3, {(1) = 0, (2) = 1, (3) = -1}), Vector(3, {(1) = 0, (2) = 0, (3) = 1})]](/support/helpjp/helpview.aspx?si=6614/file05805/math362.png)
| (2.16) |
The subsets of the restricted simple roots are:
so53 >
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![Sigma := [RSR, RSR[1 .. 2], RSR[2 .. 3], [RSR[1], RSR[3]], RSR[1 .. 1], RSR[2 .. 2], RSR[3 .. 3], []]](/support/helpjp/helpview.aspx?si=6614/file05805/math377.png)
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Here are the possible gradings for 
so53 >
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![Sigma[1], GradeSemiSimpleLieAlgebra(Sigma[1], T, method = "non-compact")](/support/helpjp/helpview.aspx?si=6614/file05805/math393.png)
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![[Vector(3, {(1) = 1, (2) = -1, (3) = 0}), Vector(3, {(1) = 0, (2) = 1, (3) = -1}), Vector(3, {(1) = 0, (2) = 0, (3) = 1})], table([0 = [R22, R11, R78, R33], 1 = [R12, R23, R37, R38], 2 = [R13, R27, R28], 3 = [R17, R18, R26], 5 = [R15], 4 = [R16], -5 = [R42], -4 = [R43], -3 = [R47, R48, R53], -2 = [R31, R57, R58], -1 = [R21, R32, R67, R68]])](/support/helpjp/helpview.aspx?si=6614/file05805/math396.png)
| (2.17) |
so53 >
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![Sigma[2], GradeSemiSimpleLieAlgebra(Sigma[2], T, method = "non-compact")](/support/helpjp/helpview.aspx?si=6614/file05805/math400.png)
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![[Vector(3, {(1) = 1, (2) = -1, (3) = 0}), Vector(3, {(1) = 0, (2) = 1, (3) = -1})], table([0 = [R78, R33, R22, R11, R37, R38, R67, R68], 1 = [R26, R27, R28, R12, R23], 2 = [R16, R13, R17, R18], 3 = [R15], -3 = [R42], -2 = [R43, R31, R47, R48], -1 = [R53, R57, R58, R21, R32]])](/support/helpjp/helpview.aspx?si=6614/file05805/math403.png)
| (2.18) |
so53 >
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![Sigma[3], GradeSemiSimpleLieAlgebra(Sigma[3], T, method = "non-compact")](/support/helpjp/helpview.aspx?si=6614/file05805/math407.png)
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![[Vector(3, {(1) = 0, (2) = 1, (3) = -1}), Vector(3, {(1) = 0, (2) = 0, (3) = 1})], table([0 = [R78, R33, R22, R11, R12, R21], 1 = [R13, R23, R37, R38], 2 = [R17, R18, R27, R28], 3 = [R16, R26], 4 = [R15], -4 = [R42], -3 = [R43, R53], -2 = [R47, R48, R57, R58], -1 = [R31, R32, R67, R68]])](/support/helpjp/helpview.aspx?si=6614/file05805/math410.png)
| (2.19) |
so53 >
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![Sigma[4], GradeSemiSimpleLieAlgebra(Sigma[4], T, method = "non-compact")](/support/helpjp/helpview.aspx?si=6614/file05805/math414.png)
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![[Vector(3, {(1) = 1, (2) = -1, (3) = 0}), Vector(3, {(1) = 0, (2) = 0, (3) = 1})], table([0 = [R78, R33, R22, R11, R23, R32], 1 = [R13, R27, R28, R12, R37, R38], 2 = [R17, R18, R26], 3 = [R16, R15], -3 = [R43, R42], -2 = [R47, R48, R53], -1 = [R31, R57, R58, R21, R67, R68]])](/support/helpjp/helpview.aspx?si=6614/file05805/math417.png)
| (2.20) |
so53 >
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![Sigma[5], GradeSemiSimpleLieAlgebra(Sigma[5], T, method = "non-compact")](/support/helpjp/helpview.aspx?si=6614/file05805/math421.png)
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![[Vector(3, {(1) = 1, (2) = -1, (3) = 0})], table([0 = [R78, R33, R22, R11, R26, R27, R28, R23, R37, R38, R53, R57, R58, R32, R67, R68], 1 = [R16, R13, R17, R18, R12, R15], -1 = [R43, R31, R47, R48, R21, R42]])](/support/helpjp/helpview.aspx?si=6614/file05805/math424.png)
| (2.21) |
so53 >
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![Sigma[6], GradeSemiSimpleLieAlgebra(Sigma[6], T, method = "non-compact")](/support/helpjp/helpview.aspx?si=6614/file05805/math428.png)
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![[Vector(3, {(1) = 0, (2) = 1, (3) = -1})], table([0 = [R78, R33, R22, R11, R12, R37, R38, R21, R67, R68], 1 = [R16, R13, R17, R18, R26, R27, R28, R23], 2 = [R15], -2 = [R42], -1 = [R43, R31, R47, R48, R53, R57, R58, R32]])](/support/helpjp/helpview.aspx?si=6614/file05805/math431.png)
| (2.22) |
so53 >
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![Sigma[7], GradeSemiSimpleLieAlgebra(Sigma[7], T, method = "non-compact")](/support/helpjp/helpview.aspx?si=6614/file05805/math435.png)
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![[Vector(3, {(1) = 0, (2) = 0, (3) = 1})], table([0 = [R78, R33, R22, R11, R13, R12, R23, R31, R21, R32], 1 = [R17, R18, R27, R28, R37, R38], 2 = [R16, R26, R15], -2 = [R43, R53, R42], -1 = [R47, R48, R57, R58, R67, R68]])](/support/helpjp/helpview.aspx?si=6614/file05805/math438.png)
| (2.23) |
so53 >
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![Sigma[8], GradeSemiSimpleLieAlgebra(Sigma[8], T, method = "non-compact")](/support/helpjp/helpview.aspx?si=6614/file05805/math442.png)
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| (2.24) |
The Query command can be used to check that each of these define a grading of .
so53 >
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![G1 := GradeSemiSimpleLieAlgebra(Sigma[1], T, method = "non-compact")](/support/helpjp/helpview.aspx?si=6614/file05805/math465.png)
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| (2.25) |
so53 >
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| (2.26) |
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See Also
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DifferentialGeometry,
CartanSubalgebra, KillingForm, LieAlgebras, PositiveRoots, Query, SimpleRoots, RootSpaceDecomposition, RestrictedRootSpaceDecomposition,
SimpleLieAlgebraData, SimpleLieAlgebraProperties
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