Cfrgtkky

When I write eta_{PV} in an equation I get a very unpleasent result:

I would like to have the subscript lower than the greek letter.
I know that can be achieved by
fontdimen16textfont2=5pt fontdimen17textfont2=5pt
which will give me a really nice result:

Problem is, this will change the subscript level in my whole equation and the rest of the document.

How can I change the subscript level lower just for eta or just locally?

You can use etastrut_{PV} so that the subscript is the depth of a strut (or more generally you can make a 0-width rule of whatever depth you need to push the subscript down)

I would advise against etastrut_{PV}.

Here is an example. I use eta^{}_{PV} in the first two cases, that end up in consecutive lines and also etastrut_{PV} in the second two cases.

As you can see, the consecutive lines where the strut construction is used are spread further apart because of the strut with the subscript.

The lines containing eta^{}_{PV}, to the contrary, are at the standard baseline skip distance from each other.

documentclass{article}



begin{document}



text text text text text text text text text

text text text text text text text text text

$eta^{}_{PV}$

text text text text text text text text text

text text text text text text text text text

text text text text text text text text text

$eta^{}_{PV}$

text text text text text text text text text

text text text text text text text text text

text text text text text text text text text

$etastrut_{PV}$

text text text text text text text text text

text text text text text text text text text

$etastrut_{PV}$

text text text text text text text text text

text text text text text text text text text

text text text text text text text text text

text text text text text text text text text



end{document}

Here is a close up of the three possibilities: first is eta_{PV}, second is eta^{}_{PV}, third is etastrut_{PV}. You can judge what's best, taking into account the problem explained above. The close up also reveals a bad kerning in the strut case.

If you load amsmath (which is recommended for documents with math), you could do

eta{smash[t]{strut}}_{PV}

but the problem with spread apart lines might appear anyway, because the subscript is very low.