Questions tagged [quantum-field-theory]
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 particle physics. Don’t combine with the [quantum-mechanics] tag.
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Correspondence between Fock state and Slater determinant
Let's consider the application of a bra to a Slater determinant (I shall neglect all constant factors or signs because they are irrelevant to my question):
\begin{align}
\langle\varphi_{k_\beta}^{(N)}|...
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What are the differences of Scalar and Pseudoscalar Yukawa Theory?
I know that some polarized interactions are forbidden.
But for unpolarized (summed over incoming and outgoing spins), are the amplitudes and decay rates of a Yukawa scalar and pseudoscalar coupled to ...
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Lorentz transformation of Creation and Annihilation operators for a real scalar field theory - MIT OCW QFT I Problem set 3 [closed]
I have been working through the MIT OCW's QFT lecture notes and problem sets, but I have come to realize that I have a fundamental misunderstanding of what is meant by how objects transform under ...
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QED with massless fermions
Consider QED such that physical mass of fermions vanishes. Is it true that their bare mass also vanishes?
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Where does the energy in a fundamental interaction come from?
When you have two electrons, they in the most likely possibility will exchange a photon, and it will cause them to repel each other. When they repel, their momentum increases, right? This momentum ...
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Why does the imaginary time Euler-Lagrange equation imply the potential goes to zero at infinite imaginary time?
On reading up about the bounce solution for false vacuum decay in S. Coleman's The Fate of the False Vacuum I it was stated that the equation
$$0 = \frac{1}{2} \frac{\partial q}{\partial \tau} . \frac{...
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Wave packet as a field configuration acting like a particle's wave function?
In Chapter 4 of his recent book Quanta and Fields, Sean Carroll uses a scalar free field to show how particles seem to emerge from field quantization.
On P.94, he talks about combining field modes ...
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$\phi^4$ quantum fields theory with vanishing physical mass
Let us consider the $\phi^4$ theory, where $\phi$ is a real scalar field, such that the physical mass vanishes.
Is it true that the bare mass also vanishes?
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A list of failed attempts towards a proof of confinement [closed]
Can one give a list of failed or open attempts (not necessarily Supersymmetric) towards a proof of confinement in 4d regarding YM or QCD?
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$i\epsilon$ prescription for finite systems [closed]
What is physical interpretation of path integral for finite time and finite epsilon (i.e without taking limits time->+-inf, epsilon->0)? Does it mean you are doing some finite temperature qft ...
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Different coupling to different kinds of sources?
Context: 1+1 dimensional scalar field coupled to a background electromagnetic field generated by two charges, q and -q situated at the points 0, a, respectively.
This article studies the effect of the ...
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Non-crossing approximation (NCA) in 'Large-$N$ expansion' (Altland & Simons CMFT)
I have a question about non-crossing approximation (NCA) stated in Condensed Matter Field Theory by Altland & Simons1. It is on page 200-203 for the 3rd edition (on page 223-227 for the 2nd ...
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QFT with massless particles
EDIT: Often in textbooks one discusses QFT with massless particles, e.g. massless fermions or scalar particles. What mass vanishes: bare or physical? or both?
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Derivation of the Equivalent Photon Approximation in Peskin and Schroeder
I am trying to reproduce the equivalent photon approximation as discussed in chapter 17.5 in Peskin and Schroeder but cannot justify equation (17.93).
The process we are considering is the scattering ...
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How might you quantise this non-polynomial action?
I am interested in the following non-polynomial action:
$$L = \sqrt{(\partial_\mu \phi \partial^\mu \phi^2 + m^2 \phi^2 -\lambda^2\phi^4)^2 + \varepsilon^2 } dx^2 $$
where $\varepsilon$ is very small....
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