Remove the call of the breqn
package.
After the operation I get
Note that subfigure
has been obsolete for several years. The official replacement is subfig
. Alternatively, use subcaption
. Note that the class already loads caption
, so subcaption
should probably be chosen.
I add a version without \left
and right
, which don't seem necessary (they rarely are in cases like this) and where the superscripts (n) are similar to the one for Gamma. More importantly, the two consecutive equations are together in a gather
environment: two equation
environments should never appear immediately after one another.
\begin{subequations}
\begin{gather}
[ \tilde{V}^{-^{(n)}} ] = [ \Gamma^{(n)} ] [ \tilde{V}^{+^{(n)}} ],
\\
[ \tilde{V}^{-\,(n)} ] = [ \Gamma^{(n)} ] [ \tilde{V}^{+\,(n)} ],
\end{gather}
\end{subequations}
In order to accommodate the split formula where you use \left
and \right
across lines, just remove all of them; for better clarity, some of the fences can be made \big
, but not more than that. Note that multline
is the environment of choice for this.
\begin{multline}
[V_m^{(n)}(z)]=[ P^{(n)} ]
\bigl( \bigl[ \exp \bigl( -j k ^{(n)} ( z-z_n) \bigr) \bigr] [ \tilde{V}^{+^{(n)}}] + \\
\bigl[ \exp \bigl( +j k ^{(n)} ( z-z_{n+1} ) \bigr) \bigr] [ \tilde{V}^{-^{(n)}} ]\bigr)
\end{multline}
If you're using LuaLaTeX or XeLaTeX, you can use the unicode-math
package. It defines all uppercase Greek letters:
\documentclass{article}
\usepackage{unicode-math}
\begin{document}
$\Alpha+\Beta=\Gamma$.
\end{document}
The result is:
This way has an advantage in that one can change the style of the letters by altering the unicode-math
options. For example \usepackage[math-style=ISO]{unicode-math}
without any other changes yields:
Also, this way alpha can be copied&pasted from the resulting PDF.
Best Answer
Some Greek capital letters look the same as Latin capitals and therefore don't have unique commands. Nu is one of them. The list of these Greek capitals is available from several sources, including
http://www.mathworks.com/matlabcentral/answers/14751-greek-alphabet-and-latex-commands-not-a-question and https://tex.stackexchange.com/a/49602/61108
From the linked TeX.SX answer the list is
Just use
N
for capital nu.