Problem with anticommutation of spinors

  • Thread starter Thread starter ansgar
  • Start date Start date
  • Tags Tags
    Spinors
ansgar
Messages
514
Reaction score
1
In e.g. Burgess and Moore - standard model a primer

it is stated that for two spinors (majorana)

\bar{\psi_1}\psi_2 = (\bar{\psi_1}\psi_2)^T = - \psi_2^T \bar{\psi_1}^T

since the spinors are anticommuting objects, thus ordering reversion gives -1

but they also state that

(\psi_1^\dagger\psi_2 )^* = (\psi_1^\dagger \psi_2)^\dagger = \psi_2^\dagger \psi_1

i.e. "without a minus sign" (explicity written in text)

I am SOOO confused, how how how can this be consistent??

best regards

37 views so far, come on I know that you can help me :)
 
Last edited:
Physics news on Phys.org
The minus sign comes from the fact that the Majorana spinors are anticommuting objects. That is, for any two Majorana spinors, a and b, we have that a * b = -b * a. This means that when we take the transpose of a product of two Majorana spinors, we get the same result as taking the reverse order of the product, but with a minus sign. So, the minus sign in the first equation comes from the fact that \bar{\psi_1}\psi_2 is the transpose of (\bar{\psi_1}\psi_2)^T. In the second equation, however, there is no minus sign because we are not taking the transpose of the product. We are simply taking the complex conjugate of it, which does not change the order of the product.
 
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
If we release an electron around a positively charged sphere, the initial state of electron is a linear combination of Hydrogen-like states. According to quantum mechanics, evolution of time would not change this initial state because the potential is time independent. However, classically we expect the electron to collide with the sphere. So, it seems that the quantum and classics predict different behaviours!
Back
Top