Feynman diagram: Two-way arrow in the fermion propagator line?
Aug 6, 2023 · This propagator must come from Majorana fermion which satisfies the real condition i.e. there is only one kind of creation or annihilation operator in plane mode expansion: …
How to count and 'see' the symmetry factor of Feynman diagrams?
Fully marked diagrams: In a Feynman diagram, the external edges are distinguishable - for clarity, let us mark them by the numbers $1,\ldots,n$ - but the half-edges on each vertex are …
Compton Scattering Lowest Order Feyman Diagram
Dec 7, 2018 · The series has diminishing constants in front of each order, as in all series expansions. These are the first order diagrams corresponding to two integrals over the …
Feynman diagram for attractive forces - Physics Stack Exchange
Nov 7, 2015 · Feynman diagrams are simply a tool to help you remember formulas: if you want to calculate the probability that two electrons will scatter off each other in so-and-so angle, you …
What do the arrows on this Feynman diagram represent?
Jul 25, 2018 · Note that the e's do not have a plus or minus. That is the correct way to write a Feynman diagram. You infer which ones are electrons and which are positrons from the …
quantum field theory - Electron-Positron annihilation Feynman …
In that sense the Feynman diagram is not a mere visual aid, but accurately reflects the physics. Under normal conditions that implies that the positron is going backwards in time, BUT we …
Feynman Diagrams for $\\phi^{4}$ theory, up to order $g^2$
Stack Exchange Network. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their …
Feynman Diagram in $\phi^3$ theory - Physics Stack Exchange
It means draw all Feynman diagrams with two external legs and two interaction vertices as each vertex contributes a power of $\lambda$. $\endgroup$ – suresh Commented May 18, 2014 at …
Feynman diagram for annihilation - Physics Stack Exchange
Apr 25, 2014 · whereas the second diagram has a fermionic internal line, requiring a propagator, $$\require{cancel} \frac{i\left(\cancel{q}+m_f\right)}{q^2-m_f^2 +i\epsilon}$$ In addition, the …
Feynman loop diagrams physical meaning - Physics Stack Exchange
Dec 15, 2020 · Note that the evaluation of one-loop Feynman diagrams usually leads to divergent expressions, which can be due to zero-mass particles in the cycle of the diagram (infrared …