Tensor[EpsilonSpinor] - create an epsilon spinor
Calling Sequences
EpsilonSpinor(indexType, spinorType, fr)
Parameters
indexType - a string, either "cov" or "con"
spinorType - a string, either "spinor" or "barspinor"
fr - (optional) the name of a defined frame
Description
Examples
See Also
The epsilon spinor is a rank 2 spinor which is fully skew-symmetric and whose component values are 1 or -1.
The command EpsilonSpinor(indexType, spinorType) returns the epsilon symbol of the type specified by indexType and spinorType in the current frame unless the frame is explicitly specified.
This command is part of the DifferentialGeometry:-Tensor package, and so can be used in the form EpsilonSpinor(...) only after executing the commands with(DifferentialGeometry); with(Tensor) in that order. It can always be used in the long form DifferentialGeometry:-Tensor:-EpsilonSpinor.
with⁡DifferentialGeometry:with⁡Tensor:
Example 1.
First create a vector bundle M with base coordinates x,y,z,t and fiber coordinates z1,z2,w1,w2.
DGsetup⁡x,y,z,t,z1,z2,w1,w2,M
frame name: M
Here are the 4 epsilon spinors one can define:
P1 ≔ EpsilonSpinor⁡cov,spinor
P1:=_DG⁡tensor,M,cov_vrt,cov_vrt,,5,6,1,6,5,−1,_DG⁡tensor,M,cov_vrt,cov_vrt,,5,6,1,6,5,−1
P2 ≔ EpsilonSpinor⁡con,spinor
P2:=_DG⁡tensor,M,con_vrt,con_vrt,,5,6,1,6,5,−1,_DG⁡tensor,M,con_vrt,con_vrt,,5,6,1,6,5,−1
P3 ≔ EpsilonSpinor⁡cov,barspinor
P3:=_DG⁡tensor,M,cov_vrt,cov_vrt,,7,8,1,8,7,−1,_DG⁡tensor,M,cov_vrt,cov_vrt,,7,8,1,8,7,−1
P4 ≔ EpsilonSpinor⁡con,spinor
P4:=_DG⁡tensor,M,con_vrt,con_vrt,,5,6,1,6,5,−1,_DG⁡tensor,M,con_vrt,con_vrt,,5,6,1,6,5,−1
Define some other manifold N.
DGsetup⁡x,y,z,t,N
frame name: N
The current frame is N. Because there are no fiber variables, one cannot calculate an epsilon spinor in this frame. To now re-calculate the epsilon spinor P1, either use the ChangeFrame command or pass EpsilonSpinor the frame name M as a third argument.
EpsilonSpinor⁡cov,spinor,M
_DG⁡tensor,M,cov_vrt,cov_vrt,,5,6,1,6,5,−1,_DG⁡tensor,M,cov_vrt,cov_vrt,,5,6,1,6,5,−1
Example 2.
The covariant and contravariant forms of the epsilon spinors are inverses of each other.
Contract the first index of P1 with the first index of P2. The result is the Kronecker delta spinor.
P5 ≔ ContractIndices⁡P2,P1,1,1
P5:=_DG⁡tensor,M,con_vrt,cov_vrt,,5,5,1,6,6,1,_DG⁡tensor,M,con_vrt,cov_vrt,,5,5,1,6,6,1
P5 &minus KroneckerDeltaSpinor⁡spinor
_DG⁡tensor,M,con_vrt,cov_vrt,,5,5,0,_DG⁡tensor,M,con_vrt,cov_vrt,,5,5,0
DifferentialGeometry, Tensor, BivectorSolderForm, CanonicalTensors, ChangeFrame, ContractIndices, KroneckerDelta, Physics[KroneckerDelta], KroneckerDeltaSpinor, PermutationSymbol, Physics[LeviCivita], SolderForm
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