All Questions
Tagged with quantum-field-theory particle-physics
1,059
questions
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What is a particle in the context of QFT with interactions?
This is a crossposting of the same question from mathoverflow: https://mathoverflow.net/q/454768/
It seems that this question was not received well there, claiming that this question is not ...
- 121
2
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64
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Can charged boson be emergent?
Dirac's initial interpretation of antimatter is the existence of Dirac Sea. However, it doesn't work for bosons since we can't invoke Fermi's exclusion principle. Goldstone boson can be emergent but ...
- 619
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61
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How should we imbed massive spin-3 in a Lorentz covariant tensor? (degree of freedom-wise)
I'm not asking for Weinberg's systematic approach. Rather, I'm more concerned with how to get the correct degrees of freedom(dof) slickly for the moment.
I believe it should be imbedded in the rank 3 ...
- 619
5
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294
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Every possible QFT from positive geometry?
Physicist Nima Arkani-Hamed has taken an interesting approach to understand fundamental physics based on geometry (specifically, positive geometry constructions). This started with his work with ...
- 2,462
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Why is there a $u$ in the middle of the feynman diagram for a quark and an antiquark annihilating?
There is a feynman diagram in chapter 2 of Griffiths Introduction to elementary particles, where a pair annihilation is taking place. I am confused as before it was written that internal lines are ...
- 11
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When to consider and when not to consider the loop contributions from light quarks?
Consider the following Lagrangian:
$$
\tag 1 \mathcal{L} = \frac{\partial_{\mu}a(x)}{f}\sum_{q}\bar{q}\gamma^{\mu}\gamma_{5}q
$$
This is a Lagrangian of the axion-like particles (ALPs) $a$ interacting ...
- 8,901
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152
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About particle number non-conservation in Quantum Field Theory
There are already similar topics with interesting answers such as When particle number can change in quantum physics? but I still don't understand much.
I often read about the non-conservation of ...
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140
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Integral of the square of the spectral density in a quantum field theory
The quantity of interest is
$$
\int_0^\infty dE \, \rho(E)^2
$$
where $\rho(E)$ is the spectral density in a Quantum Field Theory. I am wondering whether
it has any physical meaning, and
it can be ...
- 1
3
votes
1
answer
431
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Calculation of the decay rate of the $W$ boson
I am trying to calculate the decay rate of the $W^-$ boson to a charged lepton and the corresponding antineutrino.
I denote the four momentum of the $W$ boson with $q = (M_W, \vec{0})$. The momenta of ...
- 33
1
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56
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Understanding Classical Contributions to the Quantum Field Theory Path Integral
I'm a data scientist with no physics background who sometimes reads about physics in my spare time, so please take it easy on me, I know these are really obvious questions to physicists but feel free ...
- 51
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146
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Imaginary Contribution to Diagrams with one $\gamma^5$ Vertex
It is possible to write down a Feynman diagram as below for production of a Higgs boson.
I am slightly confused because the fermion-fermion-$Z$ vertex has a factor of $c_V - c_A \gamma^5$, but the $...
- 1,410
1
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0
answers
49
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Relation between matrix element of a process with its crossed processes
Consider a process in particle physics denoted by, $$(1) \quad a+b\to c+d$$ which is related to the reverse process $$(2)\quad c+d\to a+b.$$ By virtue of the hermiticity of the interaction Hamiltonian,...
- 11.8k
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83
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Axial Vector and Vector Coupling Constants for General Quarks
I am studying particle physics and a bit confused about something. The expression for the interaction vertex where a $Z$ boson couples to a pair of fermions is
$i \frac{g}{cos \theta_w} \gamma_{\mu} (...
- 1,410
1
vote
1
answer
39
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Non-leptonic weak decay with $|\Delta T=3/2|$ suppression (from "Inward bound" Pais' book)
In Abraham Pais' "Inward Bound" book at page 564 it is mentioned that if we describe the weak interactions with the usual current-current interaction (including Cabibbo angle) we still do ...
- 1,082
4
votes
1
answer
140
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Are non-virtual particles of QFT real?
Perhaps the question may seem a bit provocative, but it refers to several mathematical and, presently physical facts, pointed out a long time ago:
The Unruh effect suggests that an accelerated ...
- 1,640