The interactions tag has no wiki summary.
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How fair is it to say that all chemistry arises from failures of the ideal gas law?
I was reading here about how the ideal gas law assumes point masses and non-interaction. Is it fair to say that all chemistry arises from failures of that?
Of course, such a sweeping generalization ...
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3answers
69 views
What is the cause the light is affected by gravity? [duplicate]
I know that photons have no mass and that a photons exist only moving at the speed of light. So what is the cause that a massive astronomical object can bend a ray of light?
I have two thoughts, but I ...
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1answer
66 views
Interacting particles
We are familiar with the grand partition function for the grand canonical ensemble. This makes me wonder: what kinds of modifications would be required if the particles interacted?
Thanks.
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1answer
70 views
Gell-Mann Low Theorem and Vacuum Energy
I know that the sum of vacuum bubbles can be related to the Vacuum energy, but I'm trying to understand how this follows from the Gell-Mann Low theorem/equation. My question will use equations from ...
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1answer
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How to measure a solid-solid surface energy?
Many techniques exist to measure the surface energy between a liquid and a liquid or a liquid and a gas (see e.g. the wiki page).
Methods to measure the surface energy between a solid and a fluid are ...
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1answer
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Strong interaction and the Lagrangian for electromagnetic interaction
The Lagrangian for electromagnetic field has the following expression:
$$
L = -\frac{1}{c^{2}}A_{\alpha}j^{\alpha} - \frac{1}{8 \pi c}(\partial_{\alpha} A_{\beta})(\partial^{\alpha}A^{\beta})
$$
(I ...
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Rotating Frame with degenerate levels
I'm working with a angular momentum transition J=0 -> J=1 with no applied magnetic field; so, the upper level has degeneracy 3. This atom is coupled with an electric field propagatin in the ...
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69 views
Range of forces from mass of force carrier?
Why is $\frac{\hbar}{mc}$ a good estimate of the range of the four forces, where $m$ is the mass of the carrier particle of the force? Inputting the pion mass gives $1.4\ \mathrm{fm}$ for the hadronic ...
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1answer
91 views
A strange particle, $X$, decays in the following way: $X → π^– + p$. State what interaction is involved in this decay
A strange particle, $X$, decays in the following way: $X → π^– + p$. State what interaction is involved in this decay.
I know the answer to be weak interaction, but why is it weak interaction? What ...
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1answer
177 views
How are forces related to decays?
How are decays related to forces, what is meant by particle X decays through the, say, strong force?
The way I understand forces is by how they change the acceleration of particles with the right ...
4
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1answer
255 views
Interpretation of derivative interaction term in QFT
I am trying to understand what a term like $$ \mathcal{L}_{int} = (\partial^{\mu}A )^2 B^2 $$ with $A$ and $B$ being scalar fields for instance means. I understand how to draw an interaction term in ...
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2answers
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Interpretation of an “interaction” term
In QFT a polynomial (of degree >2) in the fields is said to be an interaction term, Ex.: $\lambda\phi^4$.
Question
Is it possible to give an interpretation to terms like $\frac{1}{\phi^n}$? (for ...
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1answer
176 views
How does the dressed Klein-Gordon propagator look in position space?
The free Klein-Gordon propagator in momentum space $\sim (p^2-m^2+i\epsilon)^{-1}$ has just a single pole at $p^2=m^2$. The passage to Fourier space is difficult but possible. The result is very ...
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3answers
243 views
Long/short-range interaction
A potential of the form $r^{-n}$ is often considered long-range, while one that decays exponentially is considered short-range.
Is this characterization simply relative/conventional, or is there a ...
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2answers
309 views
Why $\lambda\phi^4$ theory, where $\lambda>0$, is not bounded from below?
Why the following interaction, in QFT, $$\displaystyle{\cal L}_{\rm int} ~=~\frac{\lambda}{4!}\phi^4$$ where $\lambda$ is positive, represents a theory that is unstable (or unbounded from below as it ...
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2answers
155 views
Interaction speed between electric charges and magnetic materials
Einstein said that the speed of a matter in universe cannot exceed the speed of light.
Is it correct for electric force transmission speed from one electric charge to other one?
What is ...
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1answer
142 views
Interacting system and relaxation times
I got a question I'm not sure how to state precisely or is it even valid. Any help is most welcomed.
I stripped the question of all details because I wanted to emphasize my problem, but should ...
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7answers
354 views
Macroscopic laws which haven't been derived from microscopic laws
Can you think of examples where a macroscopic law coexists with a fully known microscopic law, but the former hasn't been derived from the latter (yet)? Or maybe a rule of thumb, which works but ...
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1answer
93 views
Intuitive picture for spin-fluctuations contribution to specific heat of He3
Usually when discussing Fermi liquid theory, it is stated that due to the quasiparticles effectively behaving like a free electron gas with effective mass, the specific heat is linear in $T$ at small ...
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3answers
323 views
How do magnets work?
I've read a classbook on the field theory (including EM): it perfectly describes quantitive patterns in EM-theory, but I have no luck understanding how and why it works.
I mean, magnetic substances ...
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2answers
115 views
Interacting classical strings?
May classical strings be interacting?
I would guess no, I can not see any way to break a classical closed string in two of them (the "pants" diagram); but maybe I'm missing something.
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1answer
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What's the meaning of the coupling change after a renormalization (in the 1-dim Ising Model)?
What does it mean that after the theory (1-dim Ising model here, but the question is general) is renormalized one time and $g_i\rightarrow g_i'$, that the couplings are weaker, even if the theory ...
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What sources can you recommend to understand the basics of the Coulomb interaction of particles [closed]
Maybe it's not the best place for this issue yet.
I am in graduate school. Field of knowledge of my supervisor - quantum physics - or rather, he examines the interaction of particles. Sources which ...
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1answer
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Expectation values of interacting fields
I was motivated to ask this question by the equality claimed in equation 10.3.3 of Weinberg's volume 1 of QFT books.
My interpretation of that,
If $O_s$ is a quantum field of spin $s$, $\psi_s$ is ...
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2answers
200 views
Lorentz transformation in light cone coordinates in string theory
What is the explicit form of the Lorentz transformation changing the light cone coordinates in the light cone gauge in string theory? The extended nature of the strings complicate matters, especially ...
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4answers
924 views
How can I explain why the weak nuclear interaction between individual nucleons is 'weak'?
By considering the energy-time uncertainty principle, estimate the range of the weak nuclear interaction at low energies. Compare this range to the size of a typical nucleon (for example, a proton) ...
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2answers
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How do Leptons arise from Lambda decay?
I have a question for an assignment:
Use your understanding of the quark model of hadrons and the boson model of the weak nuclear interaction to explain how leptons can arise from lambda decay, ...
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3answers
294 views
Fermionic interaction potentials
Are there any examples of fermionic particles or quasiparticles for which the interaction potential is a globally smooth function? i.e. no singularities or branch points.
As an example, in Flügge's ...
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3answers
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What is physical in the principle of local gauge invariance? [closed]
Modern theories of interactions in particle physics are gauge ones. I know how the gauge fields are introduced in equations ($D = \partial + A$). I just do not see any physical motivation in it. I am ...
