All Questions
Tagged with wavefunction quantum-field-theory
109
questions
2
votes
1
answer
45
views
Phase Coherence in the BCS wavefunction and the Cooper Pair Wavefunction
I have a couple question regarding the following BCS wavefunction ($|0\rangle$ is the vacuum state):
$$|\psi\rangle = \Pi_k \big(|u_k|+|v_k|e^{i\varphi}c^\dagger_{k\uparrow} c_{-k\downarrow}\big)|0\...
- 413
1
vote
3
answers
114
views
Has quantum measurement and particle appearance ever been modelled as a resonance effect created by the measuring device on the quantum wave?
Has anyone ever modelled quantum measurement as a resonance effect, that is created by introducing a measuring device into the quantum system?
An analogy may explain what I mean: if you take the free ...
- 141
0
votes
0
answers
73
views
Question about Witten 0+1 quantum gravity
I am trying to follow Witten’s article as much as I can.
What every physicist should know about string theory. Physics Today 68 (11), 38–43 (2015); my knowledge is very basic GR and QFT. I am really ...
- 795
0
votes
1
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113
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Question on Spinor choice in QED
In QED (see Peskin and Schoeder's book on QFT or Srednicki's book), to determine the fermion wave-function, we usually start with a spinor of a massive particle that is not moving, say
$$u_+(\vec{p}=\...
- 3,992
0
votes
1
answer
59
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Concrete understanding of QFT Hilbert space for spinor
I'm trying to understand the concepts of a spinor field in QFT. I naively understand there are two values at each spatial position $\vec{r}$: a probability amplitude and a spinor value. Is there a ...
- 148
8
votes
1
answer
401
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The wave-function in QFT
As I understand, the wave-function in QFT becomes a wave-functional dependent on fields. I have heard this told by Sean Carroll in his Biggest Ideas in the Universe lectures. Srednicki gives the $n$-...
- 525
-3
votes
1
answer
68
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Is there anything that is fundamentally real? [closed]
I've been playing around with the concept of entropy and how it can be manipulated when I came onto the complex workings of quantum waves. To my understanding, everything we know as a particle is a ...
2
votes
1
answer
69
views
Can we construct a wave function for black body radiation?
Imagine an area of space far from a black body with temperature $T$ that has emitted perfect black body radiation. So that an area of space has random photons.
Can we construct a "useful" ...
user84158
4
votes
1
answer
311
views
Why can't photons be localized as wavepackets like massive particles can? What specifically goes wrong in the math if we try to model them this way?
I've read several threads on what exactly a photon is and how it can't be modeled with a wavefunction the same way electrons can. In particular, this answer to my question about whether photons are ...
- 2,327
1
vote
1
answer
201
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Dirac Lagrangian and the meaning of $|\bar{\psi} \psi|^2$
Consider the following Dirac Lagrangian
\begin{align}
L = \bar{\psi} (i \gamma^{\mu}{\partial_{\mu}} - m) \psi
\end{align}
Suppose I extend $\psi = \psi_L + \psi_R$, with the projectors $P_L, P_R$ so ...
- 3,622
7
votes
4
answers
965
views
Wavefunction of a particle decay
Lets say we have a decay of $\rho^{0}$, in the following way. $$\rho^{0} \to \pi^{+} + \pi^{-}.$$
Is the following statement true?
$$|\rho^{0}\rangle = |\pi^{+}\rangle|\pi^{-}\rangle.$$
I don't think ...
- 299
0
votes
1
answer
210
views
In what way does QFT combine particles' wavefunctions to form fields?
If I understand correctly, in terms of the math of QFT, saying that particles are excitations in fields is mathematically equivalent to saying that a field is a representation of all possible ...
- 2,327
1
vote
2
answers
264
views
What are Test Functions in QFT (physics context)?
In terms of mode function solutions of the KG equation, the field operator can be written as
$$ \hat{\phi}(x) = \int_{R^3} d^3\textbf{p}\space \left(u_\textbf{p} \hat{a}_\textbf{p}+ u^*_\textbf{p}\hat{...
- 136
6
votes
4
answers
1k
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What is the mathematical relationship between the wave functions of QM and the fields in QFT?
To be more specific, say I have the wavefunction for the position of some arbitrary particle, but then I also have the QFT operator (is that the correct term?) modeling the position of that same ...
- 2,327
2
votes
1
answer
437
views
Does an electron's wave function collapse when it emits a photon?
I've been wondering how electromagnetic interactions between electrons are calculated if the position isn't determined until the wavefunction describing position collapses.
Does the wavefunction need ...
- 123