How to change the highness of index in tensor package?

Question

I'm having a problem with the index position in the \tensor command. When I write, for example, \tensor{A}{_\ mu}, I get a tensor with the subscript "mu" in a very low position. Is there any way I can change this? I want to raise its position a little.

Here is an example:

 \documentclass{article}
 \usepackage{tensor}
 \begin{document}

    \begin{align}
          \left( \tensor{A}{_\nu} \right) \left( \tensor{A}{_\mu} \right)
    \end{align}

 \end{document}

The problem is that the last pair of parentheses gets bigger because of the positioning of the subscript \mu:

Answer 1

Edited: Your question actually consists of two different aspects.

---

Why you should stick with the lowered subscripts with tensors

When there are no superscripts, e.g., $A_\mu$, the subscripts will be in a position you may find “not too low”. However, if there are superscripts present, e.g., $A_\mu^\nu$, then the subscripts will be lowered to give room to the superscripts.

Please note that the \indices and \tensor commands from the tensor package intentionally put the subscripts in a lowered position. So when you type something like

$\tensor{A}{_\mu} \, \tensor{M}{^a_b^c_d}$

The subscripts \mu, b and d will be sitting on the same baseline, as they should be for these two tensor objects.

If all you want is the “not lowered” version, then just type

$A_\mu$

But this, to me, destroys the meaning that A is a tensor, and IMHO leads to bad alignment.

\documentclass{article}
\usepackage{tensor}
\linespread{1.5}\selectfont% for better visual
\begin{document}
The good: $\tensor{A}{_\mu} \, \tensor{M}{^a_b^c_d}$
The bad: $A_\mu , \tensor{M}{^a_b^c_d}$
\end{document}

---

Why you shouldn’t abuse the \left and \right pair

Please don’t think that always using \left and \right is good. In fact, it is quite the opposite.

This answer by @rgrig quoted from the TeXBook, in which Donald Knuth, the inventor of TeX, explains why manual sizing delimiters are provided.

This other answer showcases examples where \left...\right is too small and when it is too big.

\documentclass{article}
\usepackage{tensor}
\linespread{1.5}\selectfont% for better visual
\begin{document}
The good: $\bigl[ (\tensor{A}{_\nu}) - (\tensor{A}{_\mu}) \bigl]$
The bad: $\left[ \left(\tensor{A}{\nu}\right) - \left(\tensor{A}{\mu}\right) \right]$
\end{document}