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Consider the following text sample:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

The fermion fields consist of two different chiral components, which
are by convention called left- and right-handed. Chiral theories like
the theory of electroweak interaction treat the chiral field
components differently. The most prominent example of this asymmetry
is the right-handed neutrino (or left-handed antineutrino) which, if
assumed massless
\footnote{The observation of neutrino oscillations requires non-zero
  neutrino masses. However, the numerical value of these masses is
  still unknown.  So far, only upper bounds have been measured,
  proving the neutrino masses to be several orders of magnitude
  smaller than masses of other fermions.}, does not
couple to any known type of interaction and is hence unobservable.

The complete gauge group of the standard model is
$SU\left(3\right)_{C}\otimes SU\left(2\right)_{T} \footnote{The
  \ensuremath{SU\left(2\right)} group is commonly displayed with the index
  \ensuremath{L} in the literature. However, to keep consistency with
  the choice of \ensuremath{T} for the weak isospin, the latter is
  used for identification throughout this thesis.}  \otimes
U\left(1\right)_{Y}$.  From this, particle interactions can be derived.

\end{document}

The footnote in math mode works as expected - maybe apart form the fact that it's a little too far from the right, but I could cope with that with some \hspace{-1ex} or alike.

What is more of the issue here is that I find that the footnote superscript might be confusing to the reader, since it looks like the expression is being squared instead. While for anybody familiar with the topic, there is no real confusion possible, the whole point of the footnote is clarifying the notation. Hence, I feel a strong desire to achieve a maximum of readability and well-definedness at this particular spot.

Any suggestions on how to treat this problem? I wouldn't mind switching to other footnote symbols (like letters), since I don't have that many footnotes - but since almost any thinkable symbol has already been used for mathematical purposes at some point, I don't feel this buys me anything...

share|improve this question
1  
It is truly necessary to insert the footnote mark inside the inline math expression? I think any danger of confusing the footnotemark with an exponent is avoided by inserting the footnote mark after the period ("full stop") that follows the inline math expression. By the way, your use of the \left( ... \right) groups introduces a lot of extra, and rather distracting, whitspace. Better to write $SU(3)_{C} \otimes SU(2)_{T} \otimes U(1)_{Y}$. –  Mico Sep 19 '13 at 14:16
1  
Guessing from the text, you have not created a marco for typing SU; you should declare \DeclareMathOperator{\SU}{SU} in you preamble. Then you can write \SU and get the correct typesetting. (Regarding your question: Footnotes in math expressions are highly discouraged.) –  Svend Tveskæg Sep 19 '13 at 14:31
1  
I would avoid the problem by inserting the footnote before entering math mode, after the words "standard model". –  Steven B. Segletes Sep 20 '13 at 5:05

2 Answers 2

up vote 6 down vote accepted

I would say that footnote in equations is not really a good practice, and you should find another way to do that...

However, perhaps you could change the mark to get a less ambiguous symbol (dagger etc.)

\renewcommand\thefootnote{\fnsymbol{footnote}}

Edit:

As pointed out in a comment, using symbols can also be confusing (since \dagger can typically be a Hermitian conjugate in quantum mechanics...); another possibility would be to use circled numbers (as proposed in an answer of this question) with the pifont package

% circled number: ①②③④⑤⑥⑦⑧⑨
\usepackage{pifont}
\renewcommand\thefootnote{\ding{\numexpr171+\value{footnote}}}
share|improve this answer
    
Assuming the dagger isn't used for some kind of notation, of course. –  You Sep 19 '13 at 14:49

Is it a typo or intention?

Please don't put footnotes inside math at all. This is the same kind of nonsense as having a footnote twice, "because the text of the footnote is the same".

People forget that the reader can't find out for sure if it's a typo or not.

If you have doubts whether something is usefull in a printed text, just try to remember if you have seen it before. Written texts are one way communication and hence depend on common understanding.

OK, if you were writing experimental vanguard lyrics...

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2  
there are some instances in which multiple references to the same footnote are warranted; one situation i can think of is for notes to entries in a table. of course, this is rather a special case. (i agree with no footnotes in math!) –  barbara beeton Sep 19 '13 at 14:47
    
@barbarabeeton Yes, you are right, in tables it is a common practice to refer repeatedly to the same annotation. As well in figures, probably anything that may have a legend. –  Keks Dose Sep 19 '13 at 15:19

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