- #1
Sven2009
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- TL;DR Summary
- why do people use free photon instead of correted one in QED process?
In many QFT textbooks, we usually see the calculations of vertex function, vacuum polarization and electron self-energy.
For example, one calculates the vacuum polarization to correct photon propagator $\langle{\Omega}|T\{A_{\mu}A_{\nu}\}|\Omega\rangle$, where $|\Omega\rangle$ is the ground state of an interaction Hamiltonian.
My questions are:
1. why do people use free photon propagator (and free electron propagator) in QED process instead of corrected one? You calculate those stuff, but you don't use them?
2. How can we guarantee that all infinites in any QED process can be absorbed by counterterms($\delta_m, Z_2...$ ect.)?
Thanks!
For example, one calculates the vacuum polarization to correct photon propagator $\langle{\Omega}|T\{A_{\mu}A_{\nu}\}|\Omega\rangle$, where $|\Omega\rangle$ is the ground state of an interaction Hamiltonian.
My questions are:
1. why do people use free photon propagator (and free electron propagator) in QED process instead of corrected one? You calculate those stuff, but you don't use them?
2. How can we guarantee that all infinites in any QED process can be absorbed by counterterms($\delta_m, Z_2...$ ect.)?
Thanks!