No spacing after \Sigma?

Question

There seems to be barely any spacing (if at all) after \Sigma, making it hard to read. Is this normal? Is there any way around it?

 $ \Sigma_{v \in V} \alpha $

Output:

Desired output:

Answer 1

You should use \sum, not \Sigma, to create a summation symbol. The \sum symbol is slightly larger than \Sigma when used in text style, and a whole lot larger when used in display style. In addition, the math type of \sum is math-op ("math operator"), whereas the math type of \Sigma is math-ord ("ordinary atom"); this strongly affects the amount of whitespace TeX inserts before and after the symbol.

\documentclass{article}
\begin{document}
$\Sigma_{i\in V}     \beta_i \quad 
 \sum_{i\in V}       \beta_i \quad
 \sum\limits_{i\in V}\beta_i \quad
{\displaystyle\sum\nolimits_{i\in V} \beta_i} \quad
 \displaystyle\sum_{i\in V} \beta_i$
\end{document}