xTras version 1.2.0

Big changes:

• Added built-in documentation.
• Added the xTrasHelp command, which opens the xTras documentation.
• Added fancy usage messages.
• All public symbols are back in the same context ("xActxTras").

Other changes:

• Added DefNiceConstantSymbol.
• Added TableauDimension.
• Added the AllContractions:nocontr message, which is generated when AllContractions returns nothing (for various reasons).
• AllContractions also takes Lists as second arguments.
• AllContractions can also handle expression with odd number of indices.
• AllContractions gives less duplicate results.
• AllContractions returns an empty list instead of throwing an exception for cases where there are no contractions.
• Changed Implode/ExplodeIndices to To/FromIndexFree.
• Changed UncontractedPairs to UncontracedIndices.
• Fixed bug in SolveTensors.
• It is now possible to change dimensions between ConstructDDIs calls.
• Removed DoTensorCollect.
• Removed ExpandPerturbationDer.
• Removed FS.
• Removed MakeEquationRule.
• Removed MetricPermutations.
• Removed OrderCoefficient.
• Removed PerturbationOfMetric.
• Removed PerturbationParameter.
• Removed PerturbationParameterOfMetric.
• Removed TensorCollect.
• Removed TensorCollector.
• Removed UnorderedPairsPermutations.
• Reset $CovDFormat and CurvatureRelations at load time.
• RiemannYoungProject and RiemannYoungRule take the option ManifestSymmetry.
• RiemannYoungRule and RiemannYoungProject no longer take a levelspec argument, but always project the Riemann and its first derivative onto their Young tableaux.
• TableauSymmetric is MMA 6 compatible.
• TermsOf now removes constants.
• The default value of Description is None.
• TimeString[60] returns "1 minute" instead of "60 seconds".
• YoungProject is faster.
• YoungTableauQ is a bit more precise.

xTras version 1.1.3

Changes:

• Added MakeTraceless.
• Added ConstructDDIs.
• Added YoungSymmetric.
• Added ToLevelSpec.
• Added ExplodeIndices and ImplodeIndices.
• Added MakeContractionAnsatz.
• Removed ContractedPairs.
• Don't define the auxiliary tensor in AllContractions if it already exists.
• AllContractions returns fewer duplicate contractions.
• SolveTensors solves by default for monomials.
• CollectTensors works better with Scalar objects.
• Made CollectTensors a bit more verbose.
• Fixed a bug in CollectTensors (where canonicalization of tensors would prevent collecting).
• The default perturbation parameter of the metric is no longer called "[Epsilon]metric", but "PerturbationParametermetric".

xTras version 1.1.2

What's new:

• Added option ManifestSymmetry to YoungSymmetrize that controls the convention of symmetrizing (i.e. first symmetric, then antisymmetric, or the other way around).
• Fixed a small bug in CollectTensors.
• Allow Young tableaux to be subsets of free indicesof expressions / tensors.
• Changed SolveTensors to allow for patterns in list of tensors to solve for.
• Fixed trying to set Bianchi identities for flat metrics.
• Fixed build file.
• Fixed: SolveConstants doesn't try to solve for numeric symbols (such as Pi).
• Replaced some Modules with Withs.
• InvarWrapper nicely aborts if the Invar database is not found.

xTras version 1.1.1

What's new:

• xTras now requires MMA 6.
• Broken xTras into multiple packages.
• Added Kretschmann scalar to SymmetricSpaceRules.
• Added ToRicci.
• Added RiemannYoungProject.
• Added option Parallelization to MapTimed. If True, MapTimed uses ParallelMap.
• Added MapTensors / MapTimedTensors.
• Added CollectConstants.
• Renamed TensorCollector to TensorWrapper.
• Renamed TensorCollect to CollectTensors.
• Renamed PreferBox/DivOf to SortCovDsToBox/Div.
• Renamed RiemannDivRule / RicciDivRule to CurvatureRelationsBianchi.
• Renamed the function KillingVectorOf to MetricOfKillingVector; the option KillingVectorOf is still named the same.
• Removed PreferBox/DivOfRule.
• Removed option MonitorSteps from MapTimed.
• Changed DerivativeOrder slightly (added thread over Plus and support for Kretschmann scalar).
• Changed IndexConfigurations to return a sorted list.
• Changed EulerDensity to return object with Scalar heads.
• Changed Invar functions to block printing of reading of Invar database.
• Changed default printing of metric perturbations to PrintAs[Perturbation] <> PrintAs[metric].
• Fixed a bug in MapTensors. It now passes options to its internal function.
• Fixed a bug in SolveTensors. (Forgot to add a levelspec to Position. Don't know why it previously worked on MMA < 9.)
• SolveTensors only sorts the tensors it solves for when the user doesn't specify them (with SolveTensors[expr==0] ).
• SolveTensors sorts the tensors to solve for by first removing TensorWrappers.
• RemoveConstants now also removes constants from expressions without tensors (resulting in 1).
• CollectTensors no longer threads over lists (as it is no longer necessary).
• AllContractions sorts answer and deletes duplicates and zero.
• Introduced UnitConstant to TensorWrapper.
• VarL performs variations w.r.t. metric determinant separately.
• MapTimed no longer has the DoTensorCollect option.
• FullSimplification doesn't call TensorCollect in the end, but ToCanonical.
• DefMetric no longer has the DefVariation option, but instead a DefMetricPerturbation option.
• DefMetricPerturbation automatically defines a metric variation (DefMetricVariation is now private).

xTras version 1.0.6

What's new:

• Added SolveTensors, which can solve (a system of) linear tensor equations, and deprecates MakeEquationRule.
• Added IndexConfigurations.
• Added PreferDifOf and PreferBoxOf functions.
• Added MapTimedIfPlus.
• Added options (Un)contractedPairs to AllContractions.
• Added options RemoveTensorCollector and Verbose to TensorCollect.
• TensorCollect prints a message if things might not have been fully collected.
• TensorCollector threads over Equal.
• TensorCollector prints like Scalar: with colored parentheses around the wrapped expression.
• New and faster algorithm for AllContractions, that contracts indices stepwise.
• Delete duplicate equations from ToConstantSymbolEquations.
• Another (sigh) and faster rewrite of TensorCollect.
• Speed improvements in SolveConstants.
• MapTimed prints info a bit nicer.
• Don't restrict ToConstantSymbolEquations to work only on things that don't contain lists (this prevented it to work on basis expressions).

xTras version 1.0.3

What's new:

• Added SortedCovDsQ
• Added AllContractions.
• Added MetricPermutations.
• MapTimed now works for generic levelspecs.
• Gave RiemannYoungRule a levelspec.
• Different implementation of Killing vectors. No longer need to issue the 'Killing' command.
• Killing vector are now defined w.r.t. to metrics, not CovDs.
• Allow for label indices in Killing vectors.
• Added version check for xTensor.
• xTras initialization messages are more like xAct.
• Automatically define metric variations by default when defining a metric.
• Removed the FD symbols and functionality.
• Renamed FS to FullSimplification.
• MyRiemannSimplify now only acts on Riccis and Riemanns, fixing a bug that appeared when it acted on other curvature tensors.
• MyRiemannSimplify checks more carefully for wrong values of $InvSimplifyLevel
• Fixed bug in MakeEquationRule that caused the LHS to still be partly present in the RHS.
• ExpandPerturbation now knows how to deal with extra curvature tensors.
• Removed ExpandPerturbationDer from VarDt function, hopefully fixing a bug that was probably caused by using SeparateMetric[] twice.
• Fixed a bug in YoungTableauQ that prevented symmetric Young tableaux from evaluating to True.

xTras version 1.0.0

Initial release.

xTras version 1.0.5

What's new:

• Made TensorCollect listable.
• ToConstantSymbolEquations handles more cases (lists, a==b==c).
• SolveConstants now takes a ! argument, which specify which variables we shouldn't solve for.
• Changed AllContractions, both the algorithm and the interface.

xTras version 1.0.4

What's new:

• Added two xCoba extensions, ComputeBasisValues and ImplodedTensorValues.
• Added Perturbation(Parameter)OfMetric.
• Added SolveConstants, which is much more similar to Solve than TensorCollectSolve was.
• Removed TensorCollectSolve.
• Renamed MyRiemannSimplify to RiemannSimplification.
• Changed MakeEquationRule such that it only works for equations (LHS == RHS).
• $RicciSign is now taken into account in various functions.
• Fixed a minor bug ( #&/ instead of #&/@ ) in PreferDivOfRule.
• Remove zeros from AllContractions.
• Don't show Def messages for temporary constants.
• Updated some usage messages.

xTras version 1.0.2

What's new:

• Implemented Killing vectors. Killing vectors can be define w.r.t. a covariant derivative while define the vector itself, e.g. DefTensor[V[-a],M,KillingVectorOf->CD].
• Fixed a bug in ConstantExprQ.