Tilde character spacing too large while using fractions [closed]

Question

I am facing a strange issue while using \tilde option in LaTex : I keep having a very large space between the tild character and the letter related to like this (in the second line) :

The fact is that, I have copy-pasted the concerned lines in a new document and this error doesn't show up anymore so I don't know if you would be able to get it :

\documentclass{article}

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{xcolor}

\begin{document}

\begin{align*}
\underline{n} \cdot \underline{\sigma} \cdot \underline{n} 
&= \frac{{\color{red}\rho g L}}{1 + \left(\frac{\partial \overline{h}}{\partial \overline{r}}\right)^2} \left(\left(2 \frac{\partial \overline{w}}{\partial \overline{z}} - \bar{p}   \right)  - 2\frac{\partial \overline{h}}{\partial \overline{r}} \left(\frac{\partial \overline{w}}{\partial \overline{r}} + \frac{\partial \overline{u}}{\partial \overline{z}} \right) - \left(\frac{\partial \overline{h}}{\partial \overline{r}} \right)^2 \left(\bar{p} - 2 \frac{\partial \overline{u}}{\partial \overline{r}}   \right) \right) = -P_T \\
&= \frac{{\color{red}\rho g L}}{1 + {\color{red} \epsilon^2} \Bigl(\frac{\partial \tilde{h}}{\partial \tilde{r}}\Bigr)^2} \left(\left(2 {\color{red}\epsilon^3} \frac{\partial \tilde{w}}{\partial \tilde{z}} - {\color{red}\epsilon} \tilde{p}   \right)  - 2 {\color{red}\epsilon} \frac{\partial \tilde{h}}{\partial \tilde{r}} \left({\color{red}\epsilon^4}\frac{\partial \tilde{w}}{\partial \tilde{r}} + {\color{red}\epsilon^2}\frac{\partial \tilde{u}}{\partial \tilde{z}} \right) - {\color{red}\epsilon^2} \left(\frac{\partial \tilde{h}}{\partial \tilde{r}} \right)^2 \left({\color{red}\epsilon}\tilde{p} - 2 {\color{red}\epsilon^3} \frac{\partial \tilde{u}}{\partial \tilde{r}}   \right) \right) = \frac{-D {\color{red}\epsilon}}{{\color{red}L^3}} (\Delta_{\tilde{r}}^{2} \tilde{h})
\end{align*}

\end{document}

Could anyone help me to understand what could be this issue related to ?

Thank you in advance,

Answer 1

I have no problem with vertical spacing of the tildes. On another hand, the formula overflows into the default margin, so I added a third line and use the geometry package. I took the opportunity to simplify the code for partial derivatives with the diffcoeff package and replaced most \overlines (for narrow letters) with a simple \bar.

Here is the code and its result:

    \documentclass{article}

    \usepackage{mathtools}
    \usepackage{diffcoeff}
    \usepackage{amssymb}
    \usepackage{xcolor}
    \usepackage[showframe]{geometry}

    \begin{document}

    \begin{align*}
    \underline{n} \cdot \underline{\sigma} \cdot \underline{n}
    &= \frac{{\color{red}\rho g L}}{1 + \left(\diffp{\bar{h}}{\bar{r}}\right)^2} \left(\left(2 \diffp{\overline{w}}{\bar{z}} - \bar{p} \right) - 2\diffp{\bar{h}}{\bar{r}} \left(\diffp{\overline{w}}{\overline{r}} + \frac{\partial \overline{u}}{\partial \overline{z}} \right) - \left(\frac{\partial \overline{h}}{\bar{r}} \right)^{\!\!2} \left(\bar{p} - 2 \diffp{\bar{u}}{\bar{r}} \right) \right) = -P_T \\
    &= \frac{{\color{red}\rho g L}}{1 + {\color{red} \epsilon^2} \Bigl(\diffp{\tilde{h}}{\tilde{r}}\Bigr)^2} \left(\left(2 {\color{red}\epsilon^3} \diffp{\tilde{w}}{\tilde{z}} - {\color{red}\epsilon} \tilde{p} \right) - 2 {\color{red}\epsilon} \diffp{\tilde{h}}{\tilde{r}} \left({\color{red}\epsilon^4}\diffp{\tilde{w}}{\tilde{r}} + {\color{red}\epsilon^2}\frac{\partial \tilde{u}}{\partial \tilde{z}} \right) - {\color{red}\epsilon^2} \left(\diffp{\tilde{h}}{\tilde{r}} \right)^{\!\!2} \left({\color{red}\epsilon}\tilde{p} - 2 {\color{red}\epsilon^3} \diffp{\tilde{u}}{\tilde{r}} \right) \right)\\
     &= \frac{-D {\color{red}\epsilon}}{{\color{red}L^3}}\Bigl (\Delta_{\tilde{r}}^{2} \tilde{h}\Bigr)
    \end{align*}

    \end{document} 

Answer 2

I am also unable to reproduce the behavior of the "tilde" accent character shown in the screen shot you posted.

I'd like so suggest that you replace all \left and \right sizing directives with \biggl and \biggr, respectively -- both to save on horizontal whitespace and to avoid sizing inconsistencies. And, I'd suggest adding line breaks in two locations to avoid overfull lines. Replacing all instances of \overline with \bar may also be a good idea.

\documentclass{article}

\usepackage{amsmath} % for "align*" environment
\usepackage{xcolor}  % for "\textcolor" macro
\providecommand\red[1]{\textcolor{red}{#1}} % handy shortcut macro

\begin{document}

\begin{align*}
\underline{n} \cdot \underline{\sigma} \cdot \underline{n}
&= \frac{\red{\rho g L}}{1 + 
  \bigl(\frac{\partial\bar{h}}{\partial\bar{r}}\bigr)^{\!2^{\mathstrut}}}
\biggl[
\biggl(2 \frac{\partial\bar{w}}{\partial\bar{z}} - \bar{p} \biggr)
- 2\frac{\partial\bar{h}}{\partial\bar{r}} \biggl(\frac{\partial\bar{w}}{\partial\bar{r}} + \frac{\partial\bar{u}}{\partial\bar{z}} \biggr)
- \biggl(\frac{\partial\bar{h}}{\partial\bar{r}} \biggr)^{\!\!2}
  \biggl(\bar{p} - 2 \frac{\partial\bar{u}}{\partial\bar{r}} \biggr)
\biggr] \\[1\jot]
&= -P_T \\
&= \frac{\red{\rho g L}}{1 + \red{\epsilon^2}
  \bigl(\frac{\partial\tilde{h}}{\partial\tilde{r}}\bigr)^{\!2^{\mathstrut}}}
\biggl[
\biggl(2 \red{\epsilon^3} \frac{\partial\tilde{w}}{\partial\tilde{z}} - \red{\epsilon} \tilde{p} \biggr)
- 2 \red{\epsilon} \frac{\partial\tilde{h}}{\partial\tilde{r}} \biggl(\red{\epsilon^4}\frac{\partial\tilde{w}}{\partial\tilde{r}} 
+ \red{\epsilon^2}\frac{\partial\tilde{u}}{\partial\tilde{z}} \biggr) \\
&\qquad - \red{\epsilon^2}
\biggl(\frac{\partial\tilde{h}}{\partial\tilde{r}} \biggr)^{\!\!2}
\biggl(\red{\epsilon}\tilde{p} - 2 \red{\epsilon^3} \frac{\partial\tilde{u}}{\partial\tilde{r}} \biggr)
\biggr] \\[1\jot]
 &= \frac{-D \red{\epsilon}}{\red{L^3}} (\Delta_{\tilde{r}}^{\!2} \tilde{h})
\end{align*}

\end{document} 

Answer 3

I found the cause of this problem : it's in the use of the "accents" package :

\usepackage{accents}

I don't know the real reason behind this issue but it seems like this package interferes a bit with the other packages that I use (\usepackage{physics}) : by deleting it I get normal tilde characters in my equations.

Thank you for everyone who tried to help despite the fact that my problem was "invisible" for all !