How to typeset properly products of glyphs with diacritics in mathmode?

Question

I have the product of two quantities with diacritics (\tilde, \hat and \bar - to be more precise), which give this ugly result. Based on your PDF viewer and zoom selection the sight might be more or less of an eyesore.

The other problem is the height at which the diacritics appear above the lowercase v, which is horrble when the d is next to it.

How can I fix these things? Is there any kind of panacea for all these problems?

Here's the code for a few samples:

\documentclass[10pt,a4paper,oneside,reqno]{amsbook}

\usepackage{pxfonts}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[english]{babel}

\begin{document}

\begin{equation}
    \begin{split}
        \tilde{d}\kern1pt\tilde{i}_c\\
        \tilde{d}\tilde{v}_{ap}
    \end{split}
\end{equation}

\begin{equation}
    \begin{split}
        \hat{d}\hat{i}_c\\
        \hat{d}\hat{v}_{ap}
    \end{split}
\end{equation}

\begin{equation}
    \begin{split}
        \bar{d}\bar{i}_c\\
        \bar{d}\bar{v}_{ap}
    \end{split}
\end{equation}

\end{document}

... and the result:

PS: Using an increased kerning between the factors of the products makes things bearable (i.e. avoids the tildes sticking together), but I think that's a really clumsy hack and I'd like to have a more elegant solution.

PS2: As per request, a sample of what I'd like to achieve (using Photoshop after LaTeX :P). Granted, the hat floats high above the v, but I prefer it that way. :)

Answer 1

Here's a solution to the d/v-problem that automatically inserts the correct kerns for the accent. The idea is taken from another answer of mine, which in turn is based on what I learned from TH. The command \ra ("raise accent") takes two arguments, the accent and the letter. The accent is then put at the same height as it would be over the letter d. This works equally well for normal text and for sub-/superscripts:

The solution also works if you replace pxfonts with mathpazo – I strongly support this suggestion of egreg (see comment to the question). However, let me point out that this only works for latin letters, so \ra \hat \gamma won't work. Note that \ra \hat d has the same effect as \hat d since the accent doesn't have to be raised.

Personally, I wouldn't raise the accents; I think it's substituting one eyesore for another.

\documentclass{article}

\usepackage{pxfonts}

\makeatletter
\newcommand*\ra[2]{%
        \begingroup
        \mathchoice{\ra@helper{#1}{#2}{\displaystyle}{\textfont}}
                   {\ra@helper{#1}{#2}{\textstyle}{\textfont}}
                   {\ra@helper{#1}{#2}{\scriptstyle}{\scriptfont}}
                   {\ra@helper{#1}{#2}{\scriptscriptstyle}{\scriptscriptfont}}%
        \endgroup
        #2%
}
\newcommand*\ra@helper[4]{%
        \def\currentfont{\the#41}%
        \def\currentskewchar{\char\the\skewchar\currentfont}%
        \setbox\tw@\hbox{\currentfont#2\currentskewchar}%
        \dimen@ii\wd\tw@
        \setbox\tw@\hbox{\currentfont#2{}\currentskewchar}%
        \advance\dimen@ii-\wd\tw@
        \rlap{$\m@th#3\kern\dimen@ii#1{\vphantom{d}\phantom{#2}}$}%
}
\makeatother

\begin{document}
\Huge
$\ra\hat d\ra\hat v_{ap}$
$A_{\ra\hat d\ra\hat v_{ap}}$
\end{document}

Answer 2

For the d/v hat perhaps

         \hat{d}\hat{v\vphantom{d}\,}\!_{ap}

does what you want:

It could perhaps be incorporated with a general macro that makes each accent macro look-ahead and insert horizontal kerns or vertical struts on a case-by-case basis.