All Questions
12
questions
-2
votes
0
answers
64
views
QED with massless fermions
Consider QED such that physical mass of fermions vanishes. Is it true that their bare mass also vanishes?
- 2,226
0
votes
0
answers
49
views
The renormalized fermionic operators do not anti-commute?
Let's say we have fermionic operators $a$ and $b$ (which anti-commute). In the context of a renormalization scheme (I am thinking specifically of Wilson's NRG, but it could be DMRG) I have a matrix $P$...
- 1,262
1
vote
0
answers
67
views
Deriving Euler-Lagrange Equations in Light-Front Quantization from the Heisenberg Equation
I'm delving into light-front quantization, with a focus on understanding the roles of good and bad fermions. Using Collins' formulation in Foundations of Perturbative QCD, we define the projectors as:
...
- 11
4
votes
0
answers
138
views
Renormalisation of the fermionic triangle loop
I am trying to renormalise the following loop diagram in the Standard Model:
$\qquad\qquad\qquad\qquad\qquad\qquad$
Using the Feynman rules, we can write the amplitude as follows:
$$ \Gamma_f \sim - ...
- 387
1
vote
0
answers
114
views
Mass shift in QED: perturbative mass terms
This question is similar to Peskin & Schroeder Chap. 7.1 ultraviolet divergence, but my doubt is still unsolved so let me ask the question.
The Peskin & Schroeder explains on p. 221 why the ...
- 353
2
votes
2
answers
426
views
External momenta in renormalizing pseudoscalar Yukawa theory
This is a follow-up question to my earlier post here:
Now suppose we have the pseudoscalar Yukawa Lagrangian:
$$
L = \frac{1}{2}\partial_\mu\phi\partial^\mu\phi-\frac{1}{2}m^2\phi^2+\bar\psi(i\not\...
- 1,783
5
votes
1
answer
198
views
Counterterms in Renormalization of a Non-Renormalizable theory (Fermi theory with four fermions)
I am studying Renormalization but I don't understand why theories which have a coupling constant with negative dimension of mass requires more and more counterterms going up with the perturbative ...
- 770
1
vote
2
answers
310
views
Functional Renormalization Group and Dirac Fermions — Yukawa Theory
I've been practicing with FRG techniques and I wanted to obtain the usual beta functions for Yukawa theory using the Wetterich equation. However, this has been more troublesome than I expected.
If I'm ...
- 22.1k
8
votes
1
answer
834
views
Renormalization Condition for Fermions
$\require{cancel}$In Peskin & Schroeder chapter 10 page 332 we have the renormalization condition
$$\left. \Sigma (\cancel{p})\right|_{\cancel{p}=m} ~=~ 0. \tag{10.40} $$
How is it possible to ...
- 735
4
votes
0
answers
1k
views
Fermion self-energy
I try to calculate the mass matrix for a massless fermion mediated by a loop of massless (right handed) neutrino and a scalar like the next diagram
The amplitude is given by:
$$ i M = \bar{u}_{s_i}(...
- 453
3
votes
1
answer
1k
views
Fermion Self-Interaction
I'm trying to think of a theory with a Fermion self-interaction, similar to the $\phi^4$ theory.
The first difficulty is of course that such a theory would have a non-renormalizable mass dimension: ...
- 2,024
17
votes
1
answer
749
views
Intuition behind mass corrections to massless fermions
I'm trying to understand the intuition behind the mass correction to massless fermions. To be concrete lets consider a theory with a massless Weyl fermion ($\psi $), as well as two massive particles, ...
- 8,995