Wicks Contraction without contractions at the same spacetime point

In summary, when computing $\mathcal{T} \langle 0 | \prod_i^Ne^{\imath \beta_i \phi(x_i)} | 0\rangle$ and ignoring contractions at the same spacetime point, inserting a complete set of states between each exponential will result in only the term 1 contributing to the expression.
  • #1
QFT1995
30
1
Homework Statement
Compute the following

$$\mathcal{T} \langle {0}| \prod_i^Ne^{\imath \beta_i \phi(x_i)} |0 \rangle$$ without contractions at the same point
Relevant Equations
Wick's theorem
If I'm computing

$$\mathcal{T} \langle 0 | \prod_i^Ne^{\imath \beta_i \phi(x_i)} | 0\rangle $$
where the contractions at the same spacetime point are ignored, can I simply insert a complete set of states (product now outside of expression) between each exponential to give

$$\mathcal{T} \prod_i^N \langle 0 |e^{\imath \beta_i \phi(x_i)} | 0\rangle$$
and then the only terms not contributing to contractions at the same spacetime point is the term 1 in the exponential which gives

$$\mathcal{T} \prod_i^N\langle 0 |1 | 0\rangle = 1$$
since
$$ \langle 0 | 0\rangle=1$$
or is this wrong?
 
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  • #2
Yes, this is correct. The only terms that would contribute to contraction at the same spacetime points are the ones where $\beta_i$ and $\beta_j$ differ by an integer, and since the $\beta_i$'s are chosen independent from each other, these terms do not exist. Therefore, the only contribution to the expression is 1.
 

Related to Wicks Contraction without contractions at the same spacetime point

What is Wicks Contraction without contractions at the same spacetime point?

Wicks Contraction without contractions at the same spacetime point is a mathematical concept used in quantum field theory to calculate the probability of interactions between particles. It involves summing over all possible paths that a particle can take between two points in spacetime without any self-interactions or contractions at the same spacetime point.

What is the significance of Wicks Contraction without contractions at the same spacetime point?

This concept is important in quantum field theory because it allows for the calculation of certain physical quantities, such as scattering amplitudes, which are essential in understanding the behavior of particles at a fundamental level. It also helps to eliminate infinities that can arise in calculations involving self-interactions.

How is Wicks Contraction without contractions at the same spacetime point calculated?

The calculation involves summing over all possible paths that a particle can take between two points in spacetime, taking into account the interactions between particles. The paths must not have any self-interactions or contractions at the same spacetime point. This is done using mathematical techniques such as Feynman diagrams.

What are the limitations of Wicks Contraction without contractions at the same spacetime point?

This concept is limited to calculations involving particles that are not interacting with themselves. It also does not take into account the effects of gravity, so it is not applicable in situations where gravity is the dominant force. Additionally, the calculations can become very complex and challenging for systems with a large number of particles.

How does Wicks Contraction without contractions at the same spacetime point relate to other concepts in physics?

This concept is closely related to other concepts in quantum field theory, such as Feynman diagrams and perturbation theory, which are used to calculate the interactions between particles. It also has connections to other areas of physics, such as quantum mechanics and general relativity, as it involves understanding the behavior of particles at a fundamental level and in the context of spacetime.

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