------------------------------------------------------------------------ 2007 3 Jan - First version of Spinors.nb. Chosen version number 0.3.0. - xTensor modified to contract and canonicalize antisymmetric metrics. Added option ExtendedFrom in DefCovD. - DefSpinStructure. 23 Jan - Eliminated warning messages RuleDelayed::rhs produced by DefSpinStructure. 16 Aug - Updated Spinors.nb for version 0.9.2 of xAct. 5 Oct - Eliminated the syntax of DefSpinStructure in which the user supplies the explicit names of the epsilon tensor and the soldering form. The reason for this is due to clashes between the indices given by the user and those used internally by DefSpinStructure. - Added the option Master->Spin_structure_name in the definition of the curvature spinors. ------------------------------------------------------------------------ 2008 2 Jan - Changes in the tensor names assigned automatically by DefSpinStructure. Some other minor changes. 4 Jan - Added Remove in the code of UndefSpinStructure in order to remove the symbol representing the spin structure. - Corrected a bug in Decomposition which arose when using the option FRiemann. 9 Jan - Added PutSolderingForm and VBundleOfSolderingForm. 16 Jan - Introduced the spinor equivalent of the metric tensor. This spinor is automatically replaced by a product of epsilon spinors. 9 May - PutSolderingForm broken in two parts. Default index arguments. 10 May - Lots of small changes for compatibility with latest xTensor/xCoba. - Added derivatives with two indices using a generalized form of MakeLinearDerivative in xTensor. 12 May - Added a type for spin derivatives - ContractSolderingForm and SeparateSolderingForm can now handle 2-index derivatives. 15 Jul - The action of Dagger upon the Box differential operator is declared by means of a downvalue, instead of an upvalue. 16 Jul - Introduced the commands BoxToCovD and BoxToCurvature. 17 Jul - Corrected a bug in the functions spindRules and tindRules. 18 Jul - DefSpinorOfTensor can now handle tensors which are complex (if a tensor is complex and we define its spinor equivalent, then we need to consider the spinor equivalent of the complex conjugate tensor). This requires a modification in the code of ContractSolderingForm in order to keep our convention about index sorting. 6 Aug - Introduced the global variables $PhiSign, $ChiSign, $PsiSign and $LambdaSign used to set the conventions in the definition of the curvature spinors. - $SolderingForms turned into a public variable. - Changed the declaration of the automatic rules which give the product of the tetra-metric with Sigma. In this way the number of such rules is reduced. 7 Aug - Changed the formatting of the operator Boxcd in order to add information about the covariant derivative cd. 10 Aug - Added the spinor equivalent of the volume element and its automatic rule of decomposition into irreducible parts. 11 Aug * First public release, with version number 0.9.0. 24 Sep - Fixed wrong sign in the traces of Sigmasoldering. 2 Oct - Solved missing sign in contractions with sigma (SpinSign). 7 Oct - Fixed signs in products of sigma's giving Sigma. 16 Oct - Added IrreducibleDecomposition. 2 Nov - Added missing symmetries on the spinor Chi when it stems from the Levi-Civita connection. Included also the case in which the torsion is present. - Added torsion spinor Omega. Changes in BoxToCurvature to include the torsion and to make the expressions consistent with the spinor form of the Ricci identities. - DefSpinCovD accepts now the option Torsion->True. - Added Posibility of definining spin structures on spacetimes with torsion. 20 Nov - Fixed special case 0 in Put/Separate/ContractSolderingForm. - SpinCovDs are now "Hermitian". 23 Nov - ContractSolderingForm acts through compatible derivatives. 1 Dec - Spinors.nb and SpinorsDoc.nb reexecuted and cleaned. * Released with version number 0.9.1. ------------------------------------------------------------------------ 2009 9 Sep - Documentation extended. - File PublicNPGHP.nb with applications of Spinors to NP and GHP separated from the main documentation file. * Released with version number 0.9.2. 9 Dec - Fixed wrong sign conventions in the code of BoxToCurvature and the code which computes the decomposition of the curvature spinor Chi (DecompositionRules[covd,Chi]). Thanks to Thomas Bäckdahl for spotting these mismatches. One needs to check the formulae in BoxToCurvature when the torsion does not vanish (currently there is a private function named $BoxTorsionSign which will show up when the torsion does not vanish). ------------------------------------------------------------------------ 2010 10 Jan * Rereleased with same version number 0.9.2. 22 Sep - Fixed wrong dummy index position in the contraction of the curvature spinors Phi and Dagger@Phi when the torsion is non-zero (when the torsion vanishes, this index position is irrelevant due to the additional symmetries of Phi). - Variable $BoxTorsionSign coincides with $TorsionSign, which replaces it now. - Fixed wrong results by the command BoxToCurvature when the torsion does not vanish. - Added command SortSpinCovDs which is the counterpart of SortCovDs for 2-index spin covariant derivatives. 30 Sep * Released with version number 1.0.0. ------------------------------------------------------------------------ 2011 11 Mar - Added definition for FirstDerQ on spin covds, as suggested by Thomas. 22 Mar - For some reason, there was an error message issued when DefSpinCovD was an extension of the Levi-Civita covd of a frozen metric. This message no longer exists. 23 Mar - When DefSpinCovD carries the option Curvature->False, then one cannot define the curvature spinors. We included some checks in the rutine ConstructRTSpinors to fix that. 17 Apr - SpinCovDQ made public. * Released with version number 1.0.1. 23 Oct - Changed sign of the spinor form of the epsilon tensor, as suggested by Thomas, to coincide with the conventions in Penrose & Rindler. Currently it uses $epsilonTetraSign. * Released with version number 1.0.2. ------------------------------------------------------------------------ 2012 28 Apr - Fixed problem in SeparateSolderingForm with dagger tensors, found by Thomas. - Added variable $xTensorVersionExpected to enforce the correct version. - Changed $PsiSign convention to match Penrose & Rindler. 5 May * Released with version number 1.0.3. ------------------------------------------------------------------------ 2013 26 Jan - TensorSymmetry renamed SymmetryOfTensor to avoid conflict with Mathematica9. 27 Jan * Released with version number 1.0.4. 16 Mar - Use VBundleIndexQ and VBundleIndexPMQ to construct the `Q and `pmQ functions. ------------------------------------------------------------------------- 2014 9 Jan - Corrected minor error in SpinCovDsOfSolderingForm pointed out by Thomas Bäckdahl. The spin covariant derivative used in DefSpinStructure was repeated in the list generated by SpinCovDsOfSolderingForm. 4 Feb - Corrected problem with non-existent options message issued by DefSpinStructure in relation to DefSpinCovD Thanks to Thomas Bäckdahl for spotting this and providing the solution. 15 Feb * Released with version number 1.0.5. 25 Apr - Added Thomas's PrintDaggerAs option in DefSpinor 10 June - Fixed problem in PrintDaggerAs. Thanks to Thomas for reporting it. 18 June - Added built-in options AddBar, AddTilde and AddDagger for PrintDaggerAs. Thanks to Thomas for supplying the code of these built-in options. 28 Sep * Released with version number 1.0.6. ------------------------------------------------------------------------- 2015 23 Aug * Released again with version number 1.0.6. ------------------------------------------------------------------------- 2016 ------------------------------------------------------------------------- 2017 ------------------------------------------------------------------------- 2018