# What is the statistical weight factor (in Pathria)?

1. Oct 14, 2012

### silverwhale

Hello Everybody,

I am working with Pathria to learn statistical mechanics, and in page 141 a quantity already defined in 129 makes a reappearance; it is the statistical weight factor. My question is, what is it? What does it mean?

To be more precise, what does the following equation in page 141 mean?
$$Q_N (V,T) = \sum'_{ \left \{ n_\varepsilon \right \}} g \left \{ n_\varepsilon \right \} e^{- \beta \sum_{\varepsilon } n_\varepsilon \varepsilon };$$
where Q_N is the canonical partition function, g is the statistical weight factor and the summation is performed over all possible sets.

Any help would be greatly appreciated.

2. Nov 13, 2015

### Ankit Dhaka

in that case its basically the degeneracy of the level.