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Tensor Index Notation

The tensind package provides a natural way to produce tensors symbols

with multiple up and down indices such as *R*^{i}_{jk}^{l} and the like in LaTeX.

In LaTeX, one loads the package in the preamble:

`\usepackage{tensind}`

`\tensordelimiter{?}`

Then in the document one just enters `$?R^i_{jk}^l?$`

where in this case the `?`

designates

the beginning and end of the tensor expression.

In LyX, using the same input inside mathed won't work: LyX reorders the

indices such that lower indices always come first, which messes things up.

Here is a workaround: All indices after the first one need to be preceded by an empty

pair of brackets (entering "\{" in mathed). The resulting LateX code

`$?R^i{}_{jk}{}^l?$`

is understood by tensind

and it even looks nice in mathed.

To streamline this, you can optionally define a math macro

(I use `\tudu`

for tensor, up-down-up) e.g. as follows: place the text

`\newcommand{\tudu}[4]{?{#1}^{#2}{}_{#3}{}^{#4}?}`

into a math box to get a math macro. Then into the still empty *formatting* box of the macro, paste

`#1^{#2}{}_{#3}{}^{#4}`

to make the display in LyX nice. The same can of course be done for other

index combinations. You now have a tensind up-down-up tensor with graphical input inside mathed. That's it.

LaTeX packages