2.3. Get (new) indices

Sometimes we need to use many indices. There are two ways to do it. We can register more symbols using AddIndices or we can ask xTensor` to generate new indices for a vbundle using NewIndexIn (it uses a combination of the last registered symbol and integer numbers). User-defined indices and computer-defined indices are kept in two different lists.

AddIndices                Add user-defined indices to a vbundle
RemoveIndices            Remove user-defined indices from a vbundle
NewIndexIn                Generate a computer-defined index
GetIndicesOfVBundle        Give n indices

Functions that return or change the available indices.

Currently there are only user-defined indices. We add some more:

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We can also remove indices, but this is a very dangerous operation because some previous expressions could get corrupted if they contain removed indices. There is no built-in command to check whether this is happening or not.

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xTensor` generates new indices using NewIndexIn

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The user-function to get any number of indices is GetIndicesOfVBundle. Note that the last argument is a list of symbols that we do not want to get:

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The indices of complex conjugated vbundles are paired, and therefore if we generate an index in one of them, automatically the complex conjugated index is generated in the other one:

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Note the information associated to an abstract index:

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Global`A

Created by Mathematica  (May 16, 2008)