# Variance and 2 point function in perturbation theory

1. Feb 9, 2015

### karlzr

When we try to find the statistical correlation of some perturbation between two positions, we always calculate the quantum 2-point function. Are these two concepts really the same?
Also, people say vaccum fluctuation is gaussian. For normalized fields, we always use Bunch-Davies initial condition $\frac{1}{\sqrt{2k}}e^{-i k \tau}$. So in which sense do we say it is gaussian?
Thanks! Any reference would be appreciated!

2. Feb 10, 2015

### karlzr

It shouldn't have been moved to quantum physics. It is absolutely cosmology! Cosmological perturbations at very early times of the universe. I should have made it clear in the previous post.

3. Feb 10, 2015

### bapowell

Yes, I too agree that this should be moved back to cosmology.

4. Feb 10, 2015

### DrDu

I think you should try the "Report" button to get attention of somebody from the staff.

5. Feb 23, 2015

### karlzr

Still need help. Thanks!