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Questions tagged [virtual-particles]

Use for computational-device notional particles which are not observable in the lab, such as "off-the-mass-shell" particles, "spurions", renormalons, merons. Do *not* use for unobserved hypothetical particles such as the graviton, or Goldstone bosons which could have been observable, but got rearranged into other particles through QFT mechanisms.

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Vacuum flucutuations = local entanglement between quantum fields?

I'm puzzled by this statement by Dieter Zeh: "Various types of quantum fluctuations (in particular vacuum fluctuations, often visualized in terms of 'virtual particles') are used to describe ...
Husserliana's user avatar
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Understanding Virtual Particles and the Mediation of Forces

When trying to understand how the electromagnetic force works in a Quantum-Mechanic context (what mediates it), one concept you will quickly encounter is that of virtual photons (and more generally ...
Giorgos G's user avatar
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Do all quantum fields fluctuate in interstellar space?

For a while now I have heard that the explanation behind the non-zero energy of vacuum space is due to quantum fluctuations. Sometimes this phenomenon has been described with virtual particles, where ...
Quantum Wonder's user avatar
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How can the attraction of opposite electric charges be explained by the exchange of virtual photons? [duplicate]

Sometimes, the electric force between two electrically charged particles is explained by the analogy of two freely floating astronauts that start throwing a ball towards each other. In this analogy, ...
a_guest's user avatar
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12 votes
3 answers
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Do particle & anti-particle pairs belong to the same field?

When trying to understand the idea of virtual particles, the explanations for it seem to imply that, for example, electron-positron pairing happens within the fluctuating electron field, so does this ...
Quantum Wonder's user avatar
1 vote
2 answers
159 views

Does the positive energy particle emitted from Hawking radiation directly equate to the amount of mass contained within the black hole?

With virtual particle-antiparticle pairs in Hawking radiation, one member of the pair falls into the black hole, typically with negative energy, while the other escapes, typically with positive energy....
Pinto's user avatar
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2 votes
0 answers
53 views

Could supermassive black holes emit massive particles as part of the Hawking radiation (even if the probability is small)? [duplicate]

Supermassive black holes should have a very low Hawking temperature and therefore would emit very low energetic photons, only when the black hole has radiated most of its mass and becomes small it ...
vengaq's user avatar
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3 votes
2 answers
204 views

Why are all observed particles on-shell?

I've been trying to self-learn how to do basic QFT calculations and I'm a little bit confused as to what's considered "an interaction". If I want to model an electron releasing a photon I ...
Opisthokont's user avatar
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28 views

Exchange Particles for IMF

Quantum field theory describes forces as being mediated by a field (e.g. gluon field for strong force, electromagnetic field for electromagnetic force). These are often modeled as a mediating boson ...
18th Shard's user avatar
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2 answers
452 views

What, specifically is meant by "particles are popping in and out of existence all the time?"

When I see that wording utilized, I have some confusion about what that means. Are the particle/anti-particle pairs each themselves popping in and out of existence, meaning the exact same particle ...
blacktopshaman's user avatar
2 votes
1 answer
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If "borrowing energy for a short time" interpretation of HUP is wrong, then how are the ranges of fundamental forces explained?

I have heard many people mention that heisenberg uncertainity prinicple doesn't really allow 'violation of energy conservaiton for a short time'. i.e, virtual particles, are just a mathematical tool. ...
Luffy curious's user avatar
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Energy and momentum conservation on a vertex in a time-ordered diagram and in a Feynman diagram

I read in the book Modern particle physics(page 114-119) from Mark Thomson that for a time-ordered diagram, the energy at each vertex is not conserved, but the momentum is. Furthermore, the energy-...
Clara's user avatar
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2 answers
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Understanding attractive/repulsive boson-mediated forces based on interference of free-space fields

I just worked through the derivations of the Yukawa interaction for scalar and spin one particles (i.e. Peskin and Schroeder, end of chapter 4, which covers the tree-level Feynman diagram). It's very ...
user34722's user avatar
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Is electron capture the exchange of a virtual $W$-boson?

Betaplus: an upquark emits a $W^+$-boson which turns it into a downquark and then decays into a positron and electron neutrino. Electron capture: an upquark emits a $W^+$-boson which is absorbed by a ...
Faalkar's user avatar
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Can the Coulomb potential as the vacuum energy shift in QED also be calculated with a field quantized in the Coulomb gauge?

This answer explains how the Coulomb-potential can be calculated as the energy shift of the (photon) ground state for 2 charges fixed in place. This calculation has been done for a covariant "...
Quantumwhisp's user avatar
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1 answer
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On Gravity and the Path Integral

The path integral, in the simplest case, usually attributes a classical action to every conceivable trajectory a particle can take between to points in spacetime. This assumes a flat, Minkowski ...
Gabriel Turner's user avatar
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1 answer
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What is screening in Quantum Field Theory and how does it influence the strength of interactions in QCD?

Question is fairly straight to the point. In particular, how does it influence the strength of particle interactions?
Mike Mutethia's user avatar
2 votes
1 answer
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How forces are mediated if virtual particles are only a mathematical artifacts? [duplicate]

I was reading this post, that discusses whether if virtual particles do exist; stating that they are only a mathematical artifact that arises from perturbation theory. My question is, if virtual ...
Álvaro Rodrigo's user avatar
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When do the experiments of the archimedes project start?

I am talking about the archimedes project, in which the gravitational effect of vacuum fluctuations will be tested using Casimir plates. https://cerncourier.com/a/scoping-out-the-einstein-telescope/
Peter's user avatar
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2 votes
0 answers
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Why don't virtual electrons get generated near protons to form atoms?

If forming an atom is a more stable state for both the electron and the proton, why don't virtual electrons get generated near protons so that they combine with them to form atoms, and then release ...
Flamethrower's user avatar
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0 answers
31 views

Do virtual particles share the same property values with the normal particles? [duplicate]

For example does a virtual electron have the same characteristic intrinsic values like mass, charge, magnetic moment etc. as a normal stable electron? Or can these range wildly and not having specific ...
Markoul11's user avatar
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2 answers
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Vacuum polarization

Interaction vertex of QED are like: \begin{equation} e \bar{\psi} {A\mkern-9mu/} \psi \end{equation} But we can't write a vertex where a particle-antiparticle pair annihilates in just 1 photon, due to ...
Matteo's user avatar
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-3 votes
3 answers
310 views

Why do gravity and electricity sometimes obey inverse square laws over the same distance scale?

Is this a chance mathematical coincidence or is there a good physical explanation for it?
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3 votes
2 answers
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Considering subatomic particles constantly appear and disappear, can we say everything around us does too?

I'm very inexperienced in this area and could use some guidance, so I would really appreciate it if you could help satisfy my intellectual curiosity. I've come across the concept that subatomic ...
Aman's user avatar
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230 views

Another "real vs virtual particle" one: calculate the full diagram or $\sigma \times \mathrm{BR}$?

I have recently been forced to think about something I always thought that I understood but that, in reality, I could not be more confused about. Suppose I want to study the LHC prospects for ...
GaloisFan's user avatar
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1 vote
1 answer
120 views

Higgs Boson and Chirality

I have seen some statements that the Higgs boson is not responsible for particles gaining mass, but rather the Higgs field is. However, as I understand it, the Higgs boson is just an excitation in the ...
18th Shard's user avatar
-1 votes
1 answer
176 views

What is meant by the term “borrowing energy from the vacuum” in quantum physics?

What is meant by “borrowing energy from the vacuum” seems like a totally illogical statement and a violation of conservation of energy
Blue5000's user avatar
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1 answer
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Are Feynman Diagrams Concealing the True Nature of Particle Scattering? [closed]

I've recently delved back into some alternative interpretations of quantum field theory. While Richard Feynman often emphasized that calculations were sufficient and discouraged fixation on the "...
VVM's user avatar
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0 answers
18 views

Are static electric and magnetic fields flows of virtual photons? [duplicate]

Many electromagnetic interactions are modeled as exchanges of a real photons: e.g. an excited electron can relax and emit a photon. Somewhere else, a photon and an electron can interact, "...
chbaker0's user avatar
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2 votes
1 answer
80 views

Interpretation of second-order term in time-dependent perturbation series (Dyson series)

$\newcommand{\ket}[1]{\left \lvert #1 \right \rangle}$ Context Consider a system described by $$H(t) = H_0 + V_0 v(t) \mathcal{O}$$ where $V_0$ defines the strength of a time dependent perturbation, $...
DanielSank's user avatar
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8 votes
1 answer
802 views

Do gravitons refer to gravity or to gravitational waves?

I am confused about what gravitons exactly are. On the one hand it is said that gravitons are presumed to represent gravity (see Wikipedia "Graviton" : "In theories of quantum gravity, ...
Moonraker's user avatar
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2 votes
0 answers
92 views

Are virtual micro black holes being considered in feynman diagrams? [closed]

I wonder if above some energies (or diagram level?) the virtual particles would rather behave (or become) like a micro black hole. Does that make sense? Could this somehow introduce a cut off above ...
Pato Galmarini's user avatar
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0 answers
39 views

Can Bernoulli's Principle be applied to subatomic particles or virtual particles or "the quantum foam"?

If we create a pair of rotary wings like those on a helicopter, and spin them in a vacuum, would it be possible for a virtual particle and anti particle pair to spawn, be split by an approaching wing, ...
Ahkilleux's user avatar
-2 votes
2 answers
218 views

Are there cases in quantum field theory's formalism were virtual particles are allowed to exceed the $c$ speed limit?

Virtual particles even today contrary to the overwhelming evidence in my opinion that they have a real effect on normal particles (i.e. Casimir effect, $g-2$ muon Fermilab experiment) are considered ...
Markoul11's user avatar
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1 vote
0 answers
34 views

Cross-section of pair creation via vitual photons not positive definite

Consider the process of pair creation via two virtual photons, i.e. $\gamma^*(k_1)+\gamma^*(k_2) \rightarrow l^-(p_1)+l^+(p_2)$, where the dilepton (or any other fermions) can be massless or massive, ...
Raymond Chen's user avatar
-2 votes
2 answers
131 views

If virtual particles don’t exist, how do laws govern them?

What exactly is the object described in a theory with virtual particles? I feel like they should behave according to laws (they seem to be useful, after all), but if they don’t exist, I can’t see how ...
Alexander Xylona's user avatar
0 votes
1 answer
294 views

Does the current form of non-perturbative QFT make all the same predictions as perturbative QFT, or is it incomplete?

For context, I watched PBS Spacetime's video on virtual particles (link goes to relevant timestamp) where they say that virtual particles aren't mathematically necessary, because the lattice version ...
Mikayla Eckel Cifrese's user avatar
3 votes
1 answer
256 views

Wiki video shows that vacuum fluctuations exist, despite that vacuum fluctuations do not exist

I have been reading this article about the quantum vacuum state, and in the section that I linked to, there is a video showing an experiment that shows visibly that quantum fluctuations are actually ...
Tachyon's user avatar
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2 votes
0 answers
78 views

Interacting QFTs and Virtual Particles

Short introduction to my understanding: As far as i understand, virtual particles are usually defined to be the internal lines in Feynman Diagrams. But we know that those are just useful tools to ...
LolloBoldo's user avatar
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23 votes
5 answers
4k views

Was Stephen Hawking's explanation of Hawking Radiation in "A Brief History of Time" not entirely accurate?

I've been looking into black holes and Hawking radiation recently (just on the surface level) and was reading "A Brief History in Time" by Stephen Hawking to understand the basics of ...
Raul Bijy's user avatar
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1 vote
1 answer
352 views

Quantum fluctuations are not real, but yet they can create observable phenomena?

I have read these What are quantum fluctuations, really? Quantum fluctuation https://www.physicsforums.com/insights/vacuum-fluctuations-experimental-practice/ and found out that quantum fluctuations ...
Tachyon's user avatar
  • 1,896
1 vote
1 answer
57 views

Virtual particles generation

I'm an engineer and I've never studied particle physics, but I like it, and I like to see Feynman diagrams and try to understand as much as I can. Looking for a Feyman diagram involving the Higgs ...
susomena's user avatar
-2 votes
1 answer
154 views

What is the difference between a positive and negative magnetic field? [closed]

I have read that a magnetic field consists of photons or virtual photons. For a given magnet, if the field emanating from one pole was examined vs that of the other pole, is there some observable ...
releseabe's user avatar
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5 votes
2 answers
247 views

Electrostatics as the infrared limit of a "sea of photons"

Textbooks giving an intro to field theory (and sometimes advanced quantum mechanics) often casually remark (in chapter one or two) that ordinary Coulomb scattering, or that classical electrostatics, ...
Linas's user avatar
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5 votes
0 answers
181 views

How do you understand displaced vertices rigorously in quantum field theory?

When you produce a long-lived particle (like charged pions, muons), it enters your detector. When you produce a short-lived particle (like the higgs, tau), the production of the particle is only seen ...
AXensen's user avatar
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0 votes
1 answer
140 views

*$n$-particle states* in QFT as irreducible representation of symmetry group?

The Quanta Magazine article titled What is a Particle? has a nice summary of various possible interpretations of particles in theoretical physics, but it appears that there is no universally accepted ...
paul230_x's user avatar
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3 votes
2 answers
395 views

What does it mean that forces are carried by virtual particles, since virtual particles are just math?

According to PBS Spacetime and other reputable sources, virtual particles are really just a handy math trick that make it easier to solve certain problems in quantum field theory, but aren't strictly ...
Mikayla Eckel Cifrese's user avatar
4 votes
4 answers
159 views

If virtual photons are just mathematical constructs, what is the real physical principle that allows EM field to give momentum to a charged particle?

If virtual photons are just mathematical constructs, what is the "real" (if such an adjective makes sense) physical principle that allows electromagnetic field to deliver momentum to a ...
Joaquín Galindo's user avatar
1 vote
0 answers
30 views

How do particles attract? [duplicate]

Particles of the same charge repel one another by "throwing" a virtual photon back and forth. Because the momentum of the virtual photon gets absorbed by the particles, they push each other ...
RobotBoyTRB's user avatar
1 vote
0 answers
136 views

Work of LSZ reduction formula

I want to know the mechanism of the LSZ reduction formula. The left side will have $\langle f|S|i\rangle$ and the right side has Fourier transform of $(\Box+m^2)$ times multiplication of Heisenberg ...
Tanmoy Pati's user avatar

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