Variance and 2 point function in perturbation theory

In summary, the conversation discusses the relationship between statistical correlation and quantum 2-point function in the context of perturbations between two positions. The concept of vacuum fluctuation and the use of Bunch-Davies initial condition for normalized fields are also mentioned. The participants also express their opinions on the appropriate category for this topic and suggest using the "Report" button for help.
  • #1
karlzr
131
2
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 vacuum 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!
 
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  • #2
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
Yes, I too agree that this should be moved back to cosmology.
 
  • #4
I think you should try the "Report" button to get attention of somebody from the staff.
 
  • #5
Still need help. Thanks!
 

What is variance in perturbation theory?

Variance in perturbation theory refers to the measure of how much a quantity or variable deviates from its expected value in a perturbative expansion. It is commonly used to quantify the uncertainty in a perturbative calculation.

How is variance calculated in perturbation theory?

In perturbation theory, variance is typically calculated by taking the square of the standard deviation of a quantity or variable. This can be done analytically or numerically, depending on the complexity of the perturbative expansion.

What is the 2 point function in perturbation theory?

The 2 point function in perturbation theory is a mathematical concept used to describe the correlation between two points in a system or process. It is commonly used in statistical mechanics and quantum field theory to study the behavior of physical systems.

How is the 2 point function related to variance in perturbation theory?

The 2 point function is related to variance in perturbation theory through its calculation. In many cases, the variance of a quantity or variable can be expressed in terms of the 2 point function, making it a useful tool for understanding and analyzing perturbative calculations.

What are some applications of variance and 2 point function in perturbation theory?

Variance and 2 point function are widely used in many fields of science, including physics, chemistry, and biology. They are particularly useful in areas such as quantum mechanics, statistical mechanics, and cosmology, where perturbative calculations are commonly used to study complex systems and processes.

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