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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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How can one of the particles on a pair of virtual particles created by vacuum fluctuations have negative energy? How does it lower black hole mass?

Assuming Stephen Hawking’s 1975 “Particle Creation by Black Holes” : “One might picture this negative energy flux in the following way. Just outside the event horizon there will be virtual pairs of ...
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Why can't a particle interaction $A + B \rightarrow C$ conserve energy and momentum at the same time?

I learned that in the Feynman diagram for electron photon scattering, the intermediate particle represented by the middle solid line must be a virtual particle because it violates energy-momentum ...
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21 views

Why accelerating observer can see Unruh radiation?

I read that uncertainty principle allows a pair of virtual particles to spawn in a vacuum as long as time is $h/E$ and nature forbid negative energy to exist, a accelerating person will see the photon ...
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382 views

Can particles popped into existence from the vacuum have electromagnetic effects on other particles?

I know my question might have problems, but I am curious about it. In quantum field theory, particle-antiparticle pairs continuously pop in and out of existence from vacuum. These particles have a ...
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1answer
55 views

If lamb shift is really due to the effect caused by virtual particles how come it only affect 1 orbital?

I was watching a video explaining virtual particle can be drawn to the positively charged necleus which explain why there is a tiny step between the higher energy level and ground state, but I'm not ...
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What are the similarities/differences between the behaviors of Quantum particles and bouncing droplets? [duplicate]

Bouncing droplets on a fluid surface show many weird behaviors of the quantum world. Look at this for example: https://arxiv.org/abs/1307.6920 They can show tunneling, double-slit interference ...
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41 views

Are vacuum-fluctuations a consequence of causality?

I'n new to QFT, and recently lerned about the propagator of a free scalar field theory in Minkowski-space, which according to our lecture notes looks like $$G(p, q) = \frac{1}{q^\mu q_\mu + M^2} \...
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2answers
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If electromagnetic wave travels in a straight line how do you explain magnetic line of forces? [closed]

Imagine a piece of bar magnet and the presence of magnetic line of forces indicated by iron filings around the magnet, this magnetic line of force is compose of virtual photon right? and since ...
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77 views

Virtual particles

I use Wikipedia to learn physics. In a recent search I found an ample description of virtual particles in terms of a discontinuous (in the present) and asymptotic distribution of these particles from -...
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1answer
125 views

Hawking said virtual particles can almost become real particles, following closed trajectories. What does that mean?

Here's hawking quote from his latest book. Brief Answers to the Big Questions "When space-time gets warped almost enough to allow travel into the past, virtual particles can almost become real ...
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1answer
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Particles, fluctuations and the quantum vacuum: is this right?

After answering a question on quantum fluctuations Could quantum fluctuations spawn real matter?, I got into conversation with E. D. Kramer (to whom thanks) and in the end it may be that we had a ...
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Could quantum fluctuations spawn real matter?

Would it be plausible for fluctuations in the QED vacuum to spawn actual matter (such as quarks, electrons the constituents of a hydrgen atom) given enough time and space?
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Lamb Shift and virtual particles [closed]

Can someone explain about the Lamb Shift?
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1answer
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If the electric force is the exchange of virtual photons, how can free electrons be accelerated by it?

I know that free electrons can't absorb photons. It is, however, known that electric forces can accelerate electrons. But if electric interactions are merely an exchange of virtual photons, how can ...
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Why do nearby charges increase the probability of virtual particles?

I'm a layperson currently reading through Matt Strassler and on his website, he states, in relation to using positronium as an example of vacuum fluctuation effects: The stronger force between the ...
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4answers
496 views

Is the term “quantum fluctuation” an aide to understanding? [closed]

I would like to ask if anyone has found a tight enough way to define the term "quantum fluctuation" so that it can become a useful rather than a misleading piece of physics terminology. Terminology ...
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3answers
700 views

Heisenberg energy uncertainty [duplicate]

I am biologist and just new to the field of quantum mechanics and trying to understand the subject by reading. It is said that virtual particles are created due to the uncertainty of energy when ...
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In terms of energy, are virtual particles an intermeidiate state between real particles and a vacuum?

What exactly is the difference between real and virtual particles? Are virtual particles just fluctuations in their quantum field? If so, how is that different to real particles?
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Feynman diagrams

Feynman diagrams are drawn on Space-time graphs. So is it possible for any particle path in that diagram to have a slope smaller than 45° or greater than 135°, i.e. can they travel faster than light? ...
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Why isn't energy conserved in time-ordered diagrams?

I'm new to particle physics, and I'm reading chapter 5 of Prof. Mark A. Thompson's "Modern Particle Physics", which talks about Time-ordered perturbation theory vs QED. However, in page 119 he wrote: ...
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1answer
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Can Virtual particles be knocked on shell (become real)?

I have read these questions: Can virtual particles be 'boosted' into becoming real particles by fields other than gravity? where dmckee specifically mentions J/Ψ meson production as a clear ...
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2answers
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Interaction of charges [duplicate]

As it is known in Physics, two point-size charges (say two electrons) interact with each other through em forces. How this is happening? do they exchange photons? And if so, then do they exchange ...
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3answers
120 views

How much virtual photons does an rest electron emits instantly, per time?

I've asked this question How much electrons can absorb a single photon? , but guys contradicted each-other, in the question about how much virtual photons does rest electron emits. One of them said ...
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1answer
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Can/do Virtual Particles have mass/energy?

Apologies, as you can tell I am not an expert... My question arose during a thought experiment regarding that elusive Dark Matter/Energy and the rate at which the universe should be expanding. It ...
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2answers
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Virtual photon does not changes energy, but changes momentum. How it could be, if energy depends on momentum?

You say virtual photon caries only momentum and changes only momentum of the particle. Momentum $p$ of electron is $v*m$. Energy of moving electron is $E=\dfrac{mc^2}{\sqrt{1-v^2/c^2}}$, which means, ...
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Free (unbound, so not bound to a nucleus) accelerated electron cannot emit/absorb a real photon?

I have read these questions: Can a free electron absorb a virtual photon even though it cannot absorb an ordinary photon? Where Michael Seifert says: It is entirely possible for a real electron ...
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3answers
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How much electrons can absorb a single photon?

In the one hand, energy can be emitted\absorbed only by a discrete portions. In the other hand - according to Coulomb law the higher distance - the lower force, because count of force lines per area ...
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1answer
195 views

Where do “virtual” particles come from? [duplicate]

Quantum physics tells us that even a perfect vacuum be populated by "virtual" pairs of subatomic particles. I have read that these particles are allowed to violate the Conservation of Matter and ...
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1answer
234 views

How to interpret the Feymann diagram of two photons scattering off each other?

I've attached a Feynmann diagram of two photons scattering with the nuclear reaction: γ + γ --> γ + γ May I ask how would one interpret this diagram? My attempt in interpreting is that the photon ...
2
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1answer
216 views

Why can there be only 3-particle vertices in Feynman diagrams? [closed]

Why can there be only 3-particle vertices in Feynman diagrams? For example, when a particle and its anti-particle annihilate to form two photons, why is its Feynmann drawn the way it is in diagram 2 (...
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2answers
118 views

According to Coulomb law, why do fixed charges interact, if they don't emit the photons?

Why does it happens, if fixed charges don't oscillate the em field?
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1answer
61 views

Why there is a distance dependence in Coulomb's law if photons can travel to infinity?

Why there is a distance dependence in coulombs law if photons can travel to infinity? Why there is distance dependence at all?
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1answer
49 views

Hawking Radiation specific clarification [duplicate]

If virtual particles on the edge of a black hole pop into existence randomly, wouldnt the likelyhood of a antiparticle generating on the inside of the black hole equal to a particle doing the same? So ...
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4answers
211 views

Is the magnetic field/force just a relativistic electric field/force or is there a fundamental difference?

I have read these questions: Difference between electric and magnetic field (relating to EEG & MEG) Can someone please explain magnetic vs electric fields? Explain the origin of magnetic fields ...
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188 views

Are EM fields made of photons or are they fundamental?

I have read these questions: Virtual photon description of B and E fields How do virtual photon cloud produce discrete magnetic field lines in bar magnet? How virtual photons give rise to electric ...
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1answer
165 views

Virtual photon exchange instantaneously

I have read these questions: Virtual Photon transmission speed of a Static Electric Field? where John Rennie's comments say: Virtual photons can travel faster than light Is there a "...
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2answers
91 views

Why aren’t photons re-absorbed into the electromagnetic field?

I understand that the quanta of electromagnetic field is a photon. Anyway, the electron field quanta is the electron. And the process of electron-positron annihilation releases two photons when the ...
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4answers
145 views

How does the spontaneous creation and destruction of matter not violate conservation of energy?

It's possible that I've grossly oversimplified this and I don't understand it properly. I have seen other questions here along similar but not identical lines. In a near vacuum, quantum effects can ...
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1answer
63 views

QED applied to two charged particles [closed]

To get the hang of how bosons actually work, could someone please provide me (the real question being, is it even possible to provide me) with a complete description of how photons are behaving and ...
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1answer
104 views

Is the QFT vacuum T-invariant?

A quantum vacuum corresponds to closed loops of particle-antiparticle pairs, in the language of Feynman diagrams. There is no relation between $E$ and $p$ for these particles, i.e., they are not on ...
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101 views

What is the difference between virtual photons and real photons? [duplicate]

I'm reading a book by Schewe and he describes the electron center as being a swarm of virtual photons. But how are they any different from actual (?) photons?
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1answer
56 views

Does vacuum has another meaning from quantum vacuum?

According to QFT. The quantum vacuum is a particular state of quantum fields; it's not a "place" where quantum fields "exist in. No problem with that. But does the word "vacuum" without the quantum ...
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1answer
26 views

Would virtual particles “dissolve” objects given enough time?

Suppose for the sake of argument that you have an object in a vacuum. According to QFT, virtual particle pairs pop in and out of existence constantly. Given enough time, would it be reasonable to ...
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2answers
115 views

What kind of particles can be virtual? Only those in the table of the Standard Model?

The cellebrated works of the teams of S. Savasta and R. J. Schoelkopf, showed that virtual particle can have effects which can be indirectly testable. See for instance the famous article L. Garziano ...
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1answer
240 views

Is an interacting QFT Hilbert space a physical particles Fock space?

There are "Lectures on Quantum Field Theory" by P.A.M. Dirac, in which he claims that QFT state space is not a separable Hilbert space. Also, I have seen some research papers (in axiomatic QFT), which ...
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Variable number of virtual particles inside neutron (relative to observer's speed)

I have read somewhere (sorry I do not know where) that the number of virtual particles in a neutron is variable depending on the speed of the observer (relative to the neutron). I understand that the ...
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3answers
191 views

Are “virtual particles” is just an analogy?

I was reading an answer in this exchange trying to explain Hawking Radiation to non-physicists (like myself) An explanation of Hawking Radiation . It informed me that the whole "virtual particle ...
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1answer
409 views

How do charged particles interact with each other?

As we know, charged particles have polarity and like charges repel each other and unlike charges attract each other, and we have Coulomb's law to find that force. But how does it work? Does it work ...
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1answer
62 views

Do masses interact with each other or not?

I want to know whether there is any interaction between masses due to gravity. To illustrate my point suppose two masses are in space. They will get attracted to each other. But is this interaction ...
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1answer
205 views

How does virtual particle explanation of Hawking radiation contradict with consistent loop description?

the picture of virtual particle pairs is categorically not the right way to think about Hawking radiation. Quite obviously it must be wrong, because it is a loop level effect, and loops in QFT have to ...