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Releases: xAct-contrib/xTras

xTras version 1.4.2

30 Oct 12:44
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  • Added RicciToRiemann.
  • Added KretschmannToRiemann.
  • ToRiemann also converts rank-2 curature tensors if the curvature relations are not enabled.
  • ToRicci also converts contractions of Riemann tensors to Ricci tensors even if the curvature relations are not enabled.

xTras version 1.4.1

20 Oct 09:23
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  • IndexConfigurations gives correct results for expressions with more than one tangent bundle.
  • EulerDensity is faster, and takes the option Verbose.
  • xTras now needs xTensor 1.1.1.

xTras version 1.4.0

23 Sep 08:32
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  • AllContractions automatically parallelizes on Mathematica 8 or newer.
  • AllContractions has an improved algorithm.
  • AllContractions directly calls the external xPerm executable, which makes it about 5x faster.
  • ConstantSymbolsOf now takes multiple arguments.
  • RiemannSimplification's error-message is more human-readable.

xTras version 1.3.3

31 Mar 17:40
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  • xTras now requires xTensor 1.1.0.
  • Products of symmetrized derivatives that commutate are now fully canonicalized.
  • Improved speed of perturbations of symmetrized derivatives.
  • Fixed two PrintAs related issues.
  • FromIndexFree is now compatible with $AutoSymmetrizeCovDs = True.
  • CollectTensors is more verbose while simplifying coefficients.

xTras version 1.3.2

03 Mar 19:13
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  • Symmetrized derivatives use the chain rule on scalar functions.
  • Improved speed of SymmetrizeCovDs in some situations.
  • SymmetrizeCovDs strips all dummy indices before caching.
  • VarD on symmetrized derivatives w.r.t. to another derivative works.
  • Symmetrized covariant derivatives pass Validate.
  • CollectTensors is faster on expressions that are (partially) collected.
  • TensorWrapper is much faster on large products (was exponential in the number of terms, is now linear).
  • Fixed warning message in SolveTensors.

xTras version 1.3.1

22 Feb 10:10
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  • Added the function ConstantSymbolsOf.
  • Added possibility (controlled by the variable $AutoSymmetrizeCovDs)
    to automatically symmetrize covariant derivatives.
  • Added caching to SymmetrizeCovDs, controlled by the "UseCache" option.
  • Improved algorithm for symmetrizing covariant derivatives in the case
    when there is no torsion and the derivative is metric-compatible.
  • Perturbation no longer expands symmetrized covariant derivatives.

xTras version 1.3.0

10 Feb 14:21
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Big changes:

  • Added functions for symmetrizing covariant derivatives (SymmetrizeCovDs and ExpandSymCovDs).
  • Added the symmetrized Riemann tensor.

Other changes:

  • Added the function ToRiemann.
  • RiemannYoungProject only projects if the Riemann tensor has its full symmetries; otherwise it does nothing.
  • RiemannYoungProject also projects Weyl and symmetrized Riemann tensors.
  • TableauSymmetric now inherits the value of its option ManifestSymmetry from YoungSymmetrize.

xTras version 1.2.3

22 Nov 10:32
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This is a small point release, adding just one function:

  • Added GradChristoffelToRiemann, which converts partial derivatives of Christoffel symbols to Riemann tensors.

xTras version 1.2.2

29 Sep 09:43
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Again a small bugfix release:

  • RemoveConstants, RemoveTensors, and TermsOf now also work on non-expanded sums.

xTras version 1.2.1

16 Aug 11:52
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This is a small bugfix release. The changes are:

  • Defining a metric with PD as its Levi-Civita derivative is no longer broken.
  • Extra curvature tensors Schouten, SchoutenCC, and EinsteinCC tensors are defined only when there
    is curvature. Furthermore, they become non-symmetric when there is torsion, and are properly
    extended, projected, and orthogonalized when needed.
  • Added torsion to the RHS of the contracted Bianchi identities returned by CurvatureRelationsBianchi.