All Questions
Tagged with quantum-field-theory hilbert-space
681
questions
9
votes
1
answer
3k
views
Definitions of the Normal Ordering Operator in CFTs and QFTs
Recall the normal ordering of bosonic operators in QFT is defined by a re-arrangement of operators to put creation operators to the left of annihilation operators in the product. This is designed to ...
- 4,176
4
votes
1
answer
437
views
The state of Indefinite metric in Quantum Electrodynamics
I am facing difficulties to grasp why indefinite metric is introduced from nowhere in QED. After searching internet, I found that this is a problem in QED, because one needs it to preserve theory's ...
- 2,071
7
votes
2
answers
2k
views
Kugo and Ojima's Canonical Formulation of Yang-Mills using BRST
I am trying to study the canonical formulation of Yang-Mills theories so that I have direct access to the $n$-particle of the theory (i.e. the Hilbert Space). To that end, I am following Kugo and ...
- 6,381
16
votes
1
answer
4k
views
When we define the S-matrix, what are "in" and "out" states?
I have seen the scattering matrix defined using initial ("in") and final ("out") eigenstates of the free hamiltonian, with
$$\left| \vec{p}_1 \cdots \vec{p}_n \; \text{out} \right\rangle
=
S^{-1}
\...
- 163
10
votes
1
answer
1k
views
In quantum field theory with a mass gap, why do states in the asymptotic future/past turn out to have a Fock space structure?
In quantum field theory with a mass gap, why do states in the asymptotic future/past turn out to have a Fock space structure? For a free quantum field theory, that's trivial, but why is that the case ...
13
votes
1
answer
5k
views
Time-ordering vs normal-ordering and the two-point function/propagator
I don't understand how to calculate this generalized two-point function or propagator, used in some advanced topics in quantum field theory, a normal ordered product (denoted between $::$) is ...
- 9,581