All Questions
Tagged with quantum-field-theory fermions
399
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Minus sign for incoming antifermions
In his Diagrammatica, The Path to Feynman Diagrams (Cambridge University Press, 1994; §4.5 "Quantum Electrodynamics", p. 88), M. Veltman reports the following Feynman rule for incoming ...
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Anticommutator Relation of Quantized Fermionic Field and Fermi–Dirac statistics: How are these related?
I'm reading the Wikipedia article about Fermionic field and have some troubles to understand the meaning following phrase:
We impose an anticommutator relation (as opposed to a commutation relation ...
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Classical fermions, where are they?
Context:
Studying the path integral formulation of QFT I stumbled upon a fairly simple statement: when doing loop expansions of a partition function:
$$Z[\eta ; \bar{\eta}] = \int [d\psi][d\bar{\psi}]...
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Renormalisation of the fermionic triangle loop
I am trying to renormalise the following loop diagram in the Standard Model:
$\qquad\qquad\qquad\qquad\qquad\qquad$
Using the Feynman rules, we can write the amplitude as follows:
$$ \Gamma_f \sim - ...
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Entanglement entropy in states with particle content
I am studying entanglement and its measurements in the context of a lattice model of the Dirac theory. The idea is that one has two bands, symmetric with respect to $E=0$, and the groundstate is ...
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Rewriting two-body operator in second-quantized form
I would like to understand the following identity for fermion field operators:
$$\psi^\dagger(x) \psi^\dagger(y) \psi(y) \psi(x) = \psi^\dagger(x) \psi(x) \psi^\dagger(y) \psi(y) - \delta(x - y) \psi^\...
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Mass shift in QED: perturbative mass terms
This question is similar to Peskin & Schroeder Chap. 7.1 ultraviolet divergence, but my doubt is still unsolved so let me ask the question.
The Peskin & Schroeder explains on p. 221 why the ...
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When does the spinor need to be in a Grassmann variable?
Follow the closed question When does the spinor need to be in a grassmann variable?
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Does the spinor in the spinor representation of the space-time symmetry
Lorentz space-time symmetry, like $so(1,...
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Diverging integral in massive fermionic field correlator
I'd like to understand the concept of the 2-particle quantum correlator for massive fermions with mass $m>0$ in 1 spatial dimension: $$C(x,y)=\langle 0|\psi(x)\psi^{\dagger}(y)|0\rangle=\int_{-\...
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Charge+Parity operator lead left-handed to right-handed
So i need to show that the, if $\psi$ is left-handed,
$$C\gamma^0\psi^*$$
Is right-handed.
So, we know that, for any $\psi$, $P_L \psi$ is left handed.
Also, for any $\omega$, is right-handed, $P_R \...
- 980
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What are self-interacting fermions?
There're a bunch of models of fermions with quartic self-interactions. There's an introduction from this wikipedia page.
For example, one can construct the Soler model of self-interacting Dirac ...
- 2,923
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405
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Fermi statistics in the Feynman rules for the Gross-Neveu model
I am trying to understand the Feynman rule for the 4-fermi interaction in the Gross-Neveu model. Based on this Peskin & Schroeder solution 12.2 and this and this Stack Exchange clarification, I ...
- 65
2
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2
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229
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Order of spinors in an equation for a Feynman diagram or contraction
I'm going over scattering theory in Peskin and Schroeder book, in his chapter on fermion scattering he wrote a specific contraction and the equation describing it
One thing he didn't mention is the ...
- 97
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Grassmann numbers for fermions in QFT
I'm studying the Grassmann variables from Polchinski's string theory textbook appendix A. On page 342,
In order to follow the bosonic discussion as closely as possible, it is useful to define states ...
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Homework, demonstrate a translation in QFT using the momentum operator [duplicate]
The question is to demonstrate the following relation in case of fermionic field:
$$ e^{i\vec{x_0}.\vec{P}} \psi(\vec{x}) e^{-i\vec{x_0}.\vec{P}} = \psi(\vec{x} - \vec{x_0})$$
where $\psi(\vec{x})$ is ...
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