Questions tagged [interactions]

Particle interactions are changes in the nature, number, or state of several particles, usually at a specific space-time point, underlying dynamics. They are represented by special "field interaction terms" in quantum field theory and normally entail interchanges of energy, momentum, and sundry quantum numbers. They include scattering, and particle creation and annihilation.

Filter by
Sorted by
Tagged with
1
vote
0answers
58 views

Field Interaction [closed]

Can someone please explain (if possible) the fundamentals of the (for lack of a better word) physical interaction that governs the behavior between fields?
1
vote
1answer
55 views

Maximum velocity of interactions

In chapter 1, Section 1, para 7, of Landau & Lifshitz, Classical Theory of Fields, they argue that if a body moves faster than maximum velocity $V_m$ of interactions, that implies we can have an ...
0
votes
1answer
66 views

Unification of the strong and electromagnetic interaction

Is it somehow possible to theoretically unify the electric charge in electromagnetic interaction with the colour charge in the strong interaction and how these charges give rise to the respective ...
0
votes
2answers
84 views

A place of space-time where the only fundamental interaction will be the gravitational forces: does make sense?

We know that there are four (fundamental forces) fundamental interactions of nature, this Wikipedia. I'm curious about if we can speculate that there exists a place of the space-time in which, after ...
1
vote
2answers
56 views

Light interaction: interaction of light waves

First of all, I would like to apologise for my English and I hope my question will be clear (even if I guess it is a quite basic question). Let's assume a person is in a closed room lighted by a ...
1
vote
1answer
389 views

Electric force much stronger than gravitational force? [duplicate]

It is commonly said that the electric force is much stronger than the gravitational force. Indeed, Coulomb's constant $k_e$ is much larger than the gravitational constant $G$ but they are measured in ...
1
vote
0answers
17 views

Quantum Field interaction transferred via “exchanging fermions” [duplicate]

In Standard Model every fundamental interaction is described by means of exchanging gluons of particular kind. It is very natural as gluons has spin with values given by inteegers, and can share the ...
1
vote
1answer
77 views

Is partition function algorithm-dependent or configuration-dependent?

I am reading this resource to learn statistical mechanics: http://blancopeck.net/Statistics.pdf I am trying to learn about the partition function, which as I understand it, is equal to the number of ...
0
votes
0answers
60 views

Properties of Feynman diagrams in Fermi's effective interaction theory

What are the properties of the Feynman diagrams in Fermi's effective interaction theory and how can one draw a Feynman diagram in this theory in relation to the Feynman diagram in the standard model ...
2
votes
0answers
97 views

Feynman rules for anomalous vertex [closed]

We can read Feynman rules directly from the lagrangian in the simplest cases, but for the following lagrangian I am a few stuck $\mathcal{L}=4g\phi\epsilon^{\mu\nu\rho\sigma}\partial_{\mu}A_{\nu}\...
0
votes
1answer
118 views

Does electric and magnetic field interact?

Can electric field or magnetic field interact with an Electromagnetic radiation? And can 2 electromagnetic radiations interact with each other? Rather than the interference effect.
0
votes
1answer
45 views

Interaction between joint qubit quantum system [closed]

Consider the following interaction Hamiltonian $$H = \hbar \mu \sigma_{x} \otimes \sigma_x = \hbar \mu ( |01 \rangle \langle 1 0 | + |10\rangle\langle 01|)$$ acting on the joint states of qubits $\...
1
vote
0answers
31 views

How fundamental electromagnetic interaction occurs in electrostatic case (say, between two resting electrons )?

Interaction between two resting charges (electrostatic case - in electrostatic field) is anyways electromagnetic (because we have only 4 fundamental interactions). Electromagnetic interaction means ...
0
votes
1answer
72 views

Decay and scattering terms in a field theory Lagrangian

Consider two genetic terms in a generic Poincare invariant quantum field theory: A trilinear term of the form $\phi_1\phi_2\phi_3$, and a quartic term of the form $\phi_1\phi_2\phi_3\phi_4$ where ...
4
votes
3answers
145 views

As the universe expands, do we have any reason to suspect further separation of the fundamental forces/interactions?

At some point, all four forces were one force. (another question: what exactly does that mean?). At some point gravity and the strong force separated out leaving the electroweak force. Then the ...
2
votes
0answers
58 views

How Forces are Represented from Quantum Computation or Entanglement Perspective?

In the fields of Quantum Computation and Entanglement there is content on the structure of quantum systems and artificial quantum systems like qubits and quantum cellular automata. I have even seen ...
41
votes
10answers
11k views

Why are there only four fundamental interactions of nature? [closed]

Is there an answer to the question why there are only four fundamental interactions of nature?
0
votes
0answers
70 views

Lagrangian term for multiple particle interactions in curved spacetime

I have the following question. Suppose one wants to describe the dynamics of $N$ interacting classical particles in a metric background given by the line element: $$ds^{2}=g_{\mu\nu}dx^{\mu}dx^{\nu}.$$...
16
votes
4answers
4k views

Other than magnetism, can any of the four fundamental forces be *repulsive*?

My son asks the above (if not in quite these words), and I am embarrassed to realize that I do not know. Can gravity, for example, or the strong or weak forces ever be repulsive? How/when?
1
vote
3answers
131 views

Inertia as a fundamental interaction

Why is Inertia not included as one of the fundamental interactions, yet gravity is included as one of the four known interactions, and there is an equivalence established between gravity and inertia.
4
votes
1answer
311 views

Feynman diagram of spin Hamiltonian

I am confused about the Feynman diagrams of spin Hamiltonian, for example, the Heisenberg model, the quartic terms like this $[1]$: \begin{align} V &= -\frac{z}{4}\frac{J}{N}\sum_{1,2,3,4}\delta_{...
1
vote
0answers
39 views

Eigenvalue equation for interacting Green's functions

Studying the articles "Topological Hamiltonian as an exact tool for topological invariants" (https://arxiv.org/abs/1207.7341) and "Simplified Topological Invariants for Interacting Insulators" (https:/...
3
votes
1answer
95 views

Understanding the behaviour of an interacting Bose gas

From the Bose-Einstein distribution it follows that a non-interacting Bose gas condenses into the Bose-Einstein condensate below a certain critical temperature. What happens when interactions are ...
-2
votes
4answers
159 views

Will anyone please explain this problem using 4 fundamental forces?

If there are only four fundamental forces (gravity,e.m.,strong,weak) in the universe and all other forces can be expressed as a function of them then consider this problem. Suppose I throw a particle '...
0
votes
0answers
217 views

Is there a fifth fundamental force? [duplicate]

When particle physicists said interaction, I interpreted it as force. So, when I heard that elementary particles interact with the Higgs field, which confers them with mass, I thought this must be a ...
2
votes
2answers
224 views

How can the gravitational force compress mass into a singularity if gravity is the weakest of the forces?

Gravity is the weakest force. I’m curious, what is the explanation for how gravity overcomes other forces and squeezes a mass down to a singularity? I get the idea of the outward pressure of fusion ...
7
votes
3answers
347 views

Why there is no 3-body (or more generally $N$-body) fundamental force?

Fundamental forces are believed to be two body interactions. However, I found myself if there is no opportunity for a 3-body or more generally $N$-body "fundamental" force. Is there a proof that any ...
0
votes
2answers
198 views

Can all light-matter interactions be reduced to the photoelectric effect, the Compton scattering, and pair production?

My book says that all interaction of light and matter can be reduced to the photoelectric effect, the Compton scattering and pair production. How true is this? What about reflection and absorption ...
7
votes
2answers
595 views

Propagator Correction in $\phi^4$ theory - why doesn't this secular growth break perturbation theory?

The free propagator for a massive $m\neq0$ real scalar field is the following: $$ G_{0}(x,y) \ = \ \int \frac{d^{4}p}{(2\pi)^4} \frac{e^{i p \cdot (x-y)}}{p^2 +m^2 - i \epsilon} $$ It is a well-...
2
votes
1answer
198 views

Is there a Quantum-Mechanics analog to QFT's quartic $\lambda \phi^{4}$ interaction?

In QFT; for the quartic-interacting real scalar field $\phi$ we have the Lagrangian density: $$ \mathcal{L} \ = \ \frac{1}{2} \left( \partial^{\mu} \phi \right)\left( \partial_{\mu} \phi \right) + \...
0
votes
0answers
26 views

How would an interaction with a single charge, and a charged weightless carrying particle behave?

We learnt about, among the other three fundamental interactions, the strong interaction. The particles that are affected by it are those with color-charge. It's carrying particles, gluons, have a ...
3
votes
3answers
3k views

why is the photopeak at a higher energy than the compton edge?

Why does the photoeffect deposit more energy than interactions via Compton scattering? Or the other way around: Why is the photopeak right (at a higher energy) than the Compton edge? https://en....
-3
votes
1answer
123 views

Four fundamental forces to explain metabolism

Apologies if this question does not make sense. I have tried looking for an answer but couldn't find one and have zero knowledge I was watching this video last night which I found fascinating. In it,...
-4
votes
2answers
415 views

Do neutrons interact with electro-magnetic fields? [closed]

Does neutrons interact with electromagnetic fields? If yes, what kind of interactions would they undergo?
12
votes
4answers
6k views

Where does the fine structure constant come from?

I have this question: Where does the fine structure constant come from? Is it derived? Is it assumed? I will be most thankful if you will also include other detailed info that you think is also good ...
5
votes
2answers
714 views

Why are derivatives in interaction terms treated differently from derivatives in the kinetic term?

I know that derivative couplings in a Lagrangian interaction, such as $$\mathcal{L}_{int} = \lambda \phi (\partial_{\mu}\phi)(\partial^{\mu}\phi)$$ bring down two momentum factors into the matrix ...
2
votes
1answer
230 views

Shouldn't dark energy be considered a fifth fundamental force?

As everyone knows from the Standard Model, there are 4 fundamental forces that describe the Universe. But isn't the dark energy, the force that makes the universe expand, different from them? Maybe ...
0
votes
3answers
418 views

How bosons do not violate conservation of energy?

As far as I understand bosons are energy packets which carry forces: e.g. Higgs bosons carry gravity. What I don't understand is, for example if we have an isolated object which constantly releases ...
0
votes
1answer
23 views

Are radiation interactions pressure, temperature dependent?

I read somewhere that gamma radiation interact with matter mostly via Compton scattering. I guess there are other type of interactions as well and probably a constant ratio between them. Does this ...
0
votes
1answer
103 views

Understanding particle scattering vs interaction

I have two questions to clarify what I am actually trying to ask through this question: What is the difference between "interaction" and "scattering" in particle physics? Does scattering of two ...
0
votes
1answer
254 views

Boson fermion interaction

Does there exists a process of boson-fermion interaction through which a virtual boson that carries force on fermionic matter turns into two (or more) fermions (with the correct conservations)? If not,...
1
vote
0answers
94 views

Visual simulation of elementary particles and interactions thererof?

Pardon me for a very stupid question, but knowing that SM predicts so much about sub-atomic particles, their interactions and whatnot, means that we have formalized these into some sorts of equations,...
3
votes
1answer
126 views

Why don't there seem to be any dimensionless fields in nature?

Scalar fields have dimension 1, spinor fields dimension 3/2, and vector bosons like the photon dimension 1. According to the principles of renormalizability (along with others), this restricts the ...
4
votes
1answer
101 views

Are interacting and free field operators equal in the Schroedinger picture?

Taking for example a scalar hermitian field (which in the free case would obey to the Klein-Gordon equation), is it true that in the Schroedinger picture the following expression hold true both in a ...
2
votes
1answer
79 views

Speed of electromagnetic interactions

We know that electromagnetic waves fly with the speed of light, but my question not about waves. Consider a very strong electromagnet that creates a substantial field 3 meters away. Then we send a ...
3
votes
1answer
55 views

Are there elementary forces acting in directions than 0 or 90 relative to their fields?

Some forces act in the same direction as their field orientation, like a gravitation. Other forces, for instance the force acting on a charged particle in a magnetic field, are perpendicular to that ...
1
vote
0answers
96 views

String interactions: intuitive vs worldsheet pictures

I am trying to understand precisely the interactions in open/closed string theories from several (interconnected) aspects: relation between the "intuitive" picture (by that I mean spatial sections of ...
0
votes
1answer
89 views

Why charged particle interaction cross section increases as the particle's energy decreases?

I'm tying to gain a little more understanding of the dose deposition profile of high energy (~100MV) protons in matter (depth dose curve - medical physics). I understand that the Bragg peak occurs ...
0
votes
1answer
145 views

Strength of gravitational waves vs. electromagnetic waves

If the recent gravitational wave's energy had reached us as visible light, how bright would it have been? Stackexchange complains about the form and brevity of the question so i add something... if it ...
4
votes
0answers
329 views

How can I see where this formula for a general vertex factor comes from?

I have been reading Srednicki from the beginning and doing all the exercises, and I hit a big roadblock at Q10.4, as I can't seem to figure out what Srednicki is doing in his solution. Luckily, I ...