I find there are two methods to calculate the amplitude in QFT. Is it equivalent?
123497
Quantum Field Theory without LSZ, how is it possible?
49060
What is the difference in the uses of $\omega t$ and $kx$ in wave equation?
29952
Time-ordering vs normal-ordering and the two-point function/propagator
152586
Does a photon have an amplitude?
92074
Why can the Euler beta function be interpreted as a scattering amplitude?
107987
How do I calculate $u(w)=\int_0^\infty \frac{1-\cos(wt)}{t}\,e^{-t}\,dt$?
33669
In what sense is a scalar field observable in QFT?
94283
Different ways finding the derivative of $\sin$ and $\cos$.
35454
Is it correct to write $\Bbb E[X]$ or $\Bbb E_{\theta}[X]$?
125215
Deriving Schrodinger equation from Klein-Gordon QFT with the definition $\psi(\textbf{x},t)\equiv \langle 0|\phi_0(\textbf{x},t)|\psi\rangle$
36131
$\sigma$-algebra vs. $\sigma$-field: is there any difference?
130752
Can we treat $\psi^{c}$ as a field independent from $\psi$?
59176
Amplitude of an electromagnetic wave containing a single photon
71599
How to prove useful property of logarithm of generating functional in QFT?
82135
Lagrangian to Hamiltonian in Quantum Field Theory
151199
Is there a formulation of Noether’s theorem for the path integral formalism?
157751
Relationship between Partial Harmonic Sum and Logarithm.