Definition of time-ordered product for Dirac spinors

In summary, the conversation discusses the time ordered product for a pair of Dirac spinors. The main question is whether the correct definition is A, where the spinor indices are kept consistent, or B, where they are switched. The speaker initially thought A was more natural, but they were getting strange results in their derivations. After realizing their mistakes, they found that the A definition was indeed correct.
  • #1
sith
14
0
I guess the answer to this question actually should be pretty obvious, but I still have problems getting it right though. I wonder about the definition of the time ordered product for a pair of Dirac spinors. In all the books I've read it simply says:

[tex]T\left\{\psi(x)\bar{\psi}(x')\right\} = \theta(t - t')\psi(x)\bar{\psi}(x') - \theta(t' - t)\bar{\psi}(x')\psi(x)[/tex]

The spinor indices are always left out. So should it be A:

[tex]T\left\{\psi_\alpha(x)\bar{\psi}_\beta(x')\right\} = \theta(t - t')\psi_\alpha(x)\bar{\psi}_\beta(x') - \theta(t' - t)\bar{\psi}_\beta(x')\psi_\alpha(x)[/tex]

or B:

[tex]T\left\{\psi_\alpha(x)\bar{\psi}_\beta(x')\right\} = \theta(t - t')\psi_\alpha(x)\bar{\psi}_\beta(x') - \theta(t' - t)\bar{\psi}_\alpha(x')\psi_\beta(x)[/tex]?

I personally think the A definition feels more natural, but when I use it in my derivations I get strange results. On the other hand, the B definition gives more reasonable results. It could simply be that I've done some mistakes in the derivations, but before I dig into those I want to know if I've got the definition right in the first place.
 
Physics news on Phys.org
  • #2
Sorry, I found what I did wrong in the derivations, and now I get it out right with the A definition. :)
 

1. What is the definition of time-ordered product for Dirac spinors?

The time-ordered product for Dirac spinors is a mathematical operation used in quantum field theory to calculate the probability amplitude for a particle to travel from one point to another. It involves arranging a series of Dirac spinors in a specific order to account for the time evolution of the system.

2. How is the time-ordered product related to Feynman diagrams?

The time-ordered product is closely related to Feynman diagrams, which are graphical representations of particle interactions in quantum field theory. The time-ordered product is used to calculate the propagator, or the probability amplitude for a particle to travel from one point to another, which is represented by a line in a Feynman diagram.

3. Why is the time-ordered product important in quantum field theory?

The time-ordered product is important in quantum field theory because it allows us to calculate the scattering amplitudes for particles, which are crucial for understanding the interactions between subatomic particles. It also plays a key role in the development of perturbation theory, which is a powerful tool for making predictions in quantum field theory.

4. How is the time-ordered product different from other mathematical operations?

The time-ordered product differs from other mathematical operations in that it takes into account the time evolution of a system. This means that the order in which the operators are arranged is important, as it affects the outcome of the calculation. It is also a non-commutative operation, meaning that the order of the operators cannot be changed without changing the result.

5. Can the time-ordered product be applied to other types of spinors?

While the time-ordered product is most commonly used with Dirac spinors, it can also be applied to other types of spinors, such as Weyl spinors or Majorana spinors. However, the specific form of the time-ordered product may differ depending on the type of spinor being used. It is a versatile mathematical tool that can be applied to various fields of physics and mathematics.

Similar threads

  • Quantum Physics
Replies
5
Views
431
Replies
1
Views
634
Replies
10
Views
1K
Replies
3
Views
618
  • Quantum Physics
Replies
6
Views
1K
  • Quantum Physics
Replies
9
Views
942
  • Quantum Physics
Replies
5
Views
2K
  • Quantum Physics
Replies
1
Views
1K
  • Quantum Physics
Replies
3
Views
930
Replies
4
Views
999
Back
Top