Where does this formula for normal ordering in QFT come from?
29952
Time-ordering vs normal-ordering and the two-point function/propagator
141561
What does it mean for a QFT to not be well-defined?
120474
Does the lagrangian contain all the information about the representations of the fields in QFT?
134718
Why is there extra minus sign in Feynman's rules for every closed fermionic loop?
38103
A No-Nonsense Introduction to Quantum Field Theory
137569
Generalising a Dirac Delta function formula in General Relativity
44224
Understanding the order() function
18564
Why is the symmetry variation $\delta_s q$ different from the ordinary variation $\delta q$?
42778
Why is the contribution of a path in Feynmans path integral formalism $\sim e^{(i/\hbar)S[x(t)]}$?
20503
Meaning of inner product $\langle \vec{r} | \psi(t)\rangle $
23037
Computing the order of $\mathrm{SL}_2(\mathbb F_p)$ as the kernel of $\mathrm{GL}_2(\mathbb F_p)$
142888
Why, intuitively, is the order reversed when taking the transpose of the product?
94230
I want to understand a trick in the derivation of the Schwinger-Dyson equations
68951
Normalization of the overlap $\langle x'|p'\rangle$
83936
Why is the Dirac mass term Hermitian if Grassmann-valued fields anticommute?
127274
Textbook on QFT in curved space-time via path integrals
100985
Effect of linear terms on a QFT