In latex, what is the best way to write multi-lined formula in subscript? Use `\atop`!
For example,
\begin{align*}
P(M_n=1) =\sigma(&w_s(\sum\limits_{j_r \in T_{nr}}\vec{U_{j_r}} \cdot \vec{C_{j_r}} - \sum\limits_{j_b \in T_{nb}}\vec{U_{j_b}} \cdot \vec{C_{j_b}} ) + \\ &w_b(\sum\limits_{j_{r_1}, j_{r_2} \in T_{nr} \atop j_{r_1} \neq j_{r_2} }\left\Vert\vec{C_{j_{r_1}}} - \vec{C_{j_{r_2}}}\right\Vert^2 - \sum\limits_{j_{b_1}, j_{b_2} \in T_{nb} \atop j_{b_1} \neq j_{b_2} }\left\Vert\vec{C_{j_{b_1}}} - \vec{C_{j_{b_2}}} \right\Vert^2) + b)
\end{align*}
will result in:
