Generating tensor indices depending on a parameter

[Sergei Savin]

Hi, 

Probably the question is very stupid but I could not find an answer. 

I need to work with the tensor with indices k_1 ... k_n, s_1 .... s_n. This is quite important since the expression for this tensor will be written via k_i and s_i where i=1...n, n is also a variable. 

I know that I can generate indices via GetIndicesOfVBundle but 

1. it gives me indices k_1,...,k_n, s_{n+1} ... s_{2n}

2. I cannot loop over i and use k_i or s_i.

I can overcome this difficulty introducing additional lists of indices and so on. 

But is it any way to do it straightforward?

Thanks in advance.

[Alfonso Jacinto García Parrado Gómez Lobo]

Hi,

as far as I know abstract indices in xTensor can only be atomic Mathematica symbols, so there's in principle no straightforward way of declaring the sort of abstract indices you need. I attach a notebook where I illustrate how to introduce these indices in a non-straightforward fashion but I haven't fully tested the code in all situations and I cannot guarantee that it is going to work in general.

Regards,

Alfonso.

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Sent: Saturday, September 24, 2016 3:00 PM
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Subject: [xAct: 1874] Generating tensor indices depending on a parameter

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