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Quantum Field Theory (QFT) is the theoretical framework describing the quantisation of classical fields which allows a Lorentz-invariant formulation of quantum mechanics. QFT is used both in high energy physics as well as condensed matter physics and closely related to statistical field theory. Use this tag for many-body quantum-mechanical problems and the theory of [tag:particle-physics]. Don’t combine with [tag:quantum-mechanics].

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I was asking myself if there is a closed formula for the following product of gamma matrices: $$\gamma_\mu\gamma_\nu \gamma_5.$$ I would like to express this matrix in terms of the basis $${\mathb …
asked Feb 1 '14 by Melquíades
4
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First remark: The correct expression is $$\langle0|\Phi(0)|p\rangle =(2\pi)^{-3/2}\left(2\sqrt{\vec{p}^{2}+m^{2}}\right)^{-1/2}N=(2\pi)^{-3/2}\left(2p^0\right)^{-1/2}N,$$ where $\vec{p}$ represents …
answered May 8 '14 by Melquíades
8
votes
1answer
I'm trying to explicitly compute the following box diagram in the Feynman-t'Hooft gauge: If I neglect the impulsion of the $s$ quark, then the final amplitude is given by $$\mathcal{A} \propto [\ba …
asked Sep 26 '14 by Melquíades
2
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0answers
I know that it is possible to derive the RGE equations from the effective potential by requiring that the first derivative with respect to the renormalization scale $\mu$ vanishes: $$ \dfrac{\mathrm{ …
asked Nov 16 '14 by Melquíades
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Since the 4-momentum must be conserved, there is no angular dependence in a 2-body decay in the CM frame. But If you are asking yourself what is the phase-space of such process, you should take a look …
answered Apr 13 '14 by Melquíades
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1answer
I am studying these lectures on effective field theories and I am having some problems to understand how the Non-Relativistic QCD (NRQCD) Lagrangian is constructed. This theory is often used to descr …
asked May 31 '14 by Melquíades
8
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4answers
My question is straightforward: Do fermionic operators associated to different species commute or anticommute? Even if these operators have different quantum numbers? How can one prove this fact in a …
asked Feb 12 '16 by Melquíades
2
votes
1answer
Let's consider an extended version of the Standard Model (SM) with a new Yukawa operator of the form $$ \sum_\ell g_\ell\bar{\ell}\ell \phi ,$$ where $\ell$ is any lepton of the SM and $\phi$ is a new …
asked Sep 6 '14 by Melquíades
4
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How can we measure meson decay constants? I am not an experimental physicst, but I think that the best way to obtain the decay constant is to study processes like $\pi^+\to \mu^+ \nu$ and extract t …
answered Jun 2 '14 by Melquíades
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0answers
Let's consider a model of New Physics in which all operator have dimension smaller than four, but which breaks explicitly $SU(2)_L$ gauge symmetry. Is this model necessarily renormalizable? Bas …
asked May 11 '15 by Melquíades
2
votes
For this process, the interaction Hamiltonian is given by: $$\mathcal{H}_{\rm int}=-\frac{g}{\sqrt 2}\left(V_{cb}\bar{b}_L\gamma^\mu c_L W^-_\mu+\bar{\nu}_L\gamma^\mu\ell_L W^+_\mu\right).$$ After i …
answered Jun 14 '14 by Melquíades
3
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1answer
What is the importance of dimension six operators in the study of physics beyond the Standard Model? Are these operators more relevant than dimension five operators like $HHFF$ or operators with deriv …
asked Apr 20 '14 by Melquíades