Have you encountered a spacing problem with the command \tilde? To show what I mean, let's take a look at $\tilde{f}_{k}$ and $f_k$. Do you notice that the subscript $k$ is awkwardly spaced from $\tilde{f}$ in $\tilde{f}_k$? The same problem occurs if I use \widetilde: $\widetilde{f}_k$. Even with \dot, \hat, and \bar commands, the same problem occurs: $\dot{f}_k$, $\hat{f}_k$, and $\bar{f}_k$.

I know there is a way to re-adjust the spacing by using \!, so $\tilde{f}_{\!k}$ and $\tilde{f}_{\!\!k}$ would become $\tilde{f}_{\!k}$ and $\tilde{f}_{\!\!k}$, respectively. They look a lot better than $\tilde{f}_k$, although the spacing isn't the same as in $f_k$ (which annoys me a little bit).

For some other characters, the spacing is ok. For example, $\tilde{a}_k$ produces $\tilde{a}_k$, which has the same spacing as $a_k$. It seems the problem occurs with tall characters like $d$ and $t$: $\tilde{d}_k$ and $\tilde{t}_k$ (comparing with $d_k$ and $t_k$). The problem is lessened with deep characters like $g$ and $y$: $\tilde{g}_k$ and $\tilde{y}_k$ (comparing with $g_k$ and $y_k$).

Is this a bug? If it is, by whom? By MathJax, by StackExchange, or by my browser? I don't recall seeing this problem in LaTeX.

Edit. I got a response from a MathJax developer. If you are interested, see here.

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    $\begingroup$ by the way, spacing can be specified quite precisely $f_k\hat f_{\hspace{0pt}k}\hat f_{\hspace{-0.5pt}k}\hat f_{\hspace{-1pt}k}\hat f_{\hspace{-1.5pt}k}$ $f_k\hat f_{\hspace{0pt}k}\hat f_{\hspace{-0.5pt}k}\hat f_{\hspace{-1pt}k}\hat f_{\hspace{-1.5pt}k}$ (this does not excuse the problem) $\endgroup$ Commented Jul 20, 2020 at 4:13

1 Answer 1


I can confirm that it is a MathJax (as opposed to SE) issue, as I can reproduce it outside of this site. It doesn't happen in LaTeX.

As a workaround, you can use $\tilde {f_k}$: $\tilde {f_k}$

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    $\begingroup$ Thank you. I thought there was something wrong with my browser for a bit. And nice solution. I didn't think of that. $\endgroup$ Commented Jul 17, 2020 at 21:43
  • $\begingroup$ Glad I could help. I don't know much about MathJax, so I don't know what could be happening down below the surface. If I'm not wrong, the MathJax developers pop up here from time to time, so maybe we'll get an authoritative answer. $\endgroup$ Commented Jul 18, 2020 at 1:02
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    $\begingroup$ Alternatively one can fill in bug report at github.com/mathjax/MathJax/issues, that is something they should read. However any fix would probably go to Mathjax v3, but this site still uses v2, so... $\endgroup$
    – Sil
    Commented Jul 18, 2020 at 13:15
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    $\begingroup$ @Sil Thanks. I reported. $\endgroup$ Commented Jul 18, 2020 at 16:45
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    $\begingroup$ @Sil The MathJax team seems to continue publishing bug-releases for MathJax v2 and the latest one is v2.7.8, so there's some hope to have v2.7.9 in the future that fixes this bug.. $\endgroup$ Commented Jul 19, 2020 at 1:11
  • $\begingroup$ @Sil But the site isn’t going to use v2 forever, correct? $\endgroup$ Commented Jul 19, 2020 at 13:35
  • $\begingroup$ @Saad Okay, that sounds promising. RadialArmSaw hopefully not, but there are some technical reasons they have not switched, see math.meta.stackexchange.com/questions/30901/… $\endgroup$
    – Sil
    Commented Jul 19, 2020 at 16:17

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