3

Easy question here but haven't been able to find the answer online. I am trying to create the following symbol in math mode: an i, with a bar over it, and then an asterisk as a superscript to the entire object.

My initial attempt was the simple $\bar{i}^*$, however, the asterisk seems to fall under the bar. I need the asterisk to look as if it's the superscripts for all of \bar{i}. My other (unsuccessful) attempts have included using the empty group {} to create a gap between the \bar{i} and the superscript, using \mbox{} to delimit the \bar{i} as admitting a superscript, and simply playing around with placement. In all these cases, however, I still end up with an asterisk that looks to be below or at the same height as the bar, not above. Any suggestions?

  • I'm not sure to understand what your doubt is; if you compare $A^*$ and $\bar{i}^*$, you'll see that the asterisks are at the same height (which is the right one, by the way). If it was the whole “starred i” to have a bar, it would be $\overline{i^*}$. – egreg Aug 19 '16 at 9:31
2

In my opinion, what is being asked here is just a way to circumvent the rule, stated in The TeXbook, p. 291, l. 16–17, that prevents ${\bar{i}}^{*}$ from having the desired effect; for this, it suffices to say, e.g., ${\bar{i}{}}^{*}$, whereby no extra height is introduced.

Here is a complete, compilable source code:

\documentclass[a4paper]{article}
\usepackage[T1]{fontenc} % comment or uncomment as preferred

\begin{document}
Compare: $\bar{i}^{*}$, ${\bar{i}}^{*}$, ${\bar{i}{}}^{*}$, $\bar{i}\strut^{*}$.
\end{document}

And here is the output it produces:

Output of the above code

Note that, in the fourth case, the asterisk is rised slightly more than in the third one.

2

This works.

\documentclass[12pt]{article}



\begin{document}
    \begin{equation}
     \bar i^* \quad {\bar i}^* \quad {\bar i\vphantom{\Big|}}^* \quad 
     {\bar i {\Large\mathstrut}}^*
        \end{equation}
\end{document}

enter image description here

1

it's traditional in math publishing to use an undotted i if a diacritic is to be placed over it. \imath is the command for this letter. (there's a matching \jmath.)

\documentclass{article}
\begin{document}

$ \bar{\imath}^* \quad \bar{\imath}\strut^* $

$ \bar{\jmath}^* \quad \bar{\jmath}\strut^* $

\end{document}

output of example code

if you feel the asterisk is too low (although it is at the proper place; compare it with $T^*$ for example), you can insert something taller to raise it. a \strut is used here; the \mathstrut doesn't change the position.

0

You need a larger object to superscript. As an example use \strut:

enter image description here

\documentclass{article}

\begin{document}

$\bar{i}^*\ \bar{i}\strut^*$

\end{document}

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