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...
\left( ... \right)
groups introduces a lot of extra, and rather distracting, whitspace. Better to write$SU(3)_{C} \otimes SU(2)_{T} \otimes U(1)_{Y}$
.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.)