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QuantumT

Quantum fluctuation origin?

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Been googling for an answer to this for weeks now, but to no avail, so I turn to you guys as the last resort.

When two virtual particles emerge in a vacuum (fluctuation), where does the energy come from?
I've heard claims that the energy comes from the future (but not from a reliable source). Is that true? (Or is it from the past?)
Does the energy involved in quantum fluctuation really travel in time? Or is the origin undetermined?

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Heisenberg's Uncertainty Principle, which states that for a brief enough period of time, the energy of a particle, system, or even a volume of space, can be a range of values, as long as the Heisenberg inequality is satisfied.

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28 minutes ago, MigL said:

Heisenberg's Uncertainty Principle, which states that for a brief enough period of time, the energy of a particle, system, or even a volume of space, can be a range of values, as long as the Heisenberg inequality is satisfied.

So, no origin and no time travel?

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51 minutes ago, QuantumT said:

Been googling for an answer to this for weeks now, but to no avail, so I turn to you guys as the last resort.

When two virtual particles emerge in a vacuum (fluctuation), where does the energy come from?
I've heard claims that the energy comes from the future (but not from a reliable source). Is that true? (Or is it from the past?)
Does the energy involved in quantum fluctuation really travel in time? Or is the origin undetermined?

Vacuum energy: https://en.wikipedia.org/wiki/Vacuum_energy

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13 minutes ago, QuantumT said:

Yes, I've read that page. As I understand it, "the nature of vacuum energy" remains an unsolved problem. So we just don't know where it comes from, is that right?

My knowledge is too superficial to elaborate but it contains energies, or field excitations, that are not quantized and therefore cannot normally interact with particles of the standard model and if they do, only briefly when they combine. As to their nature,  I might guess that they could be called sub-quantum excitations or particles.

Edited by StringJunky

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15 minutes ago, QuantumT said:

Yes, I've read that page. As I understand it, "the nature of vacuum energy" remains an unsolved problem. So we just don't know where it comes from, is that right?

I can't see where it says that? OK. Got it. I am rather sceptical about that sentence. I suspect it may have been sneaked in by a "free energy nut". :) (The article it links to for support makes some passing reference to "controversial attempts to extract energy" - I think they are being too kind.)

The "Origin" section explains why it arises, but isn't very clear. Simplifying a lot, quantum theory says that values of fields always oscillate. Because there is no such thing as negative energy, they can't oscillate around zero (or half the time they would be negative). So they oscillate about some value greater than zero. As a result, the average value is more than zero. (The Origin section might make a bit more sense after that ... maybe?)

8 minutes ago, QuantumT said:

I see I'm not the only one wondering about the origin:

https://www.researchgate.net/post/Where_does_vacuum_energy_come_from (it's a forum thread)

Some suggest the energy comes from photons. Could that be right?

Noooo.... Random speculations from random people!!!

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Every field fluctuates through the quantum harmonic oscillator. This involves to an extent the uncertainty principle. Zero point energy is based on this. 

Any field can generate particles as all particles are field excitations. If the particle exceeds a quanta then the particle is real instead of virtual.

If the particle is below a quanta then it's oft denoted virtual. The number density of particles in a field will correspond to the energy density of the field on a probability function.

To get a complete answer then QFT and path integrals will lead you there however there is a significant learning curve.

 

Edited by Mordred

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Thanks guys, I now better understand quantum field oscillation. Question is, does the energy jump/leap from field to field (disappear/reappear)?

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No energy is a property it doesn't exist on its own.

Energy is defined as the ability to perform work. So when someone states field energy simply think of it as the fields ability to perform work.

Keep in mind a field is an abstract object that describes a collection of mathematical values/objects such as scalar quantities/ vectors/spinors or tensors at each coordinate.

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3 hours ago, Mordred said:

No energy is a property it doesn't exist on its own.

Energy is defined as the ability to perform work. So when someone states field energy simply think of it as the fields ability to perform work.

Keep in mind a field is an abstract object that describes a collection of mathematical values/objects such as scalar quantities/ vectors/spinors or tensors at each coordinate.

Thanks for clarifying that.

One final question: Is space divided into stationary quantum fields, or are they moving around?

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2 hours ago, QuantumT said:

Thanks for clarifying that.

One final question: Is space divided into stationary quantum fields, or are they moving around?

All fields share the same space or more accurately under GR, spacetime.  Some fields affect other fields, while some only affect certain other fields.

 Good example is the limited fields the Neutrino family of particles. As they are weakly interactive they do not affect the strong or EM fields. 

 As your asking about QM specifically and want help understanding particle production under either QM or QFT.  You will want to study "action" as in the principle of least action but more involved.  The action of a field describes the (Observable) ie measurable quantities. In QM or QFT the creation and annihilator operators are used to determine probable particle number densities of a field. 

https://en.m.wikipedia.org/wiki/Creation_and_annihilation_operators

You will see it mentions the Uncertainty principle.Those operators  will correspond to the external lined on Feymann diagrams. 

Now the virtual particles individually cannot cause action. So they are described in the internal lines as part of the propogators.  Now QFT works well under SR the reason being gravity is so weakly interactive. However all matter and force fields contribute to the Stress energy momentum of GR so they all contribute to the spacetime curvature.

The stress energy tensor is how we describe the influence of mass using the four momentum and four velocity. Mass being described as resistance to inertia change. In essence the action of a field or collection of fields will correspond to the kinematics of all interactions. We describe that using the those vectors.

In QM your operators being position and momentum. Under QFT we use field and momentum.

 

Edited by Mordred

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