0

Let's take a look at the quantum vacuum (which, on closer inspection is not faithful as it shows constant periodic behavior):

enter image description here

There surely is something going on. Now I don't want to speak about the reality of virtual particles, as both sides in this debate are defensible.

No, I want to get some information about the nature of time in this whirling world of colors (if we should believe our eyes...). Does a virtual particle travel forward as well as backward in time, the backward traveling part representing anti-particles? A virtual particle carries a wide spectrum of energies and 3-momenta, which are independent from one another as the virtual is not on mass-shell. But what about time? If we take another look at the dizzying image, process doesn't seem to go forward nor backward in time. Or both at the same time. Can we somehow see this in the expression for the virtual particle?

To be clear, I don't ask about the reality of virtual particles. That's a question we could argue about endlessly. No, I'm asking if we can say anything sensibly about the direction in time virtual particles travel in. If their mathematical description can inform us. I can remember reading they fluctuate in time.

This question comes close but doesn't answer mine.

MatterGauge
  • 1
  • 2
    Does this answer your question? Are vacuum fluctuations really happening all the time? – John Rennie May 29 '22 at 09:16
  • @JohnRennie No. It's not about them really happening or not. We could argue about that endlessly. I explicit said that in my question. I ask if they go back and forth in time. Can we see that in their mathematical expression? – MatterGauge May 29 '22 at 09:57
  • 2
    You have been misinformed: both sides of the debate are not defensible. Virtual particles are a pure construction of the perturbation approach to solving problems. – Oбжорoв May 29 '22 at 10:10
  • 2
    @Felicia the fluctuations don't go backwards and forward in time because they don't exist! – John Rennie May 29 '22 at 10:15
  • @JohnRennie That's up for debate, like I wrote. Some say yes some say no. For sure they cant be detected. But they are routinely used in qft and have math attached. That's what I ask about. – MatterGauge May 29 '22 at 10:52
  • 2
    @Felicia it is not up for debate. The only people who say the vacuum fluctuates are people who have not studied quantum field theory. Measurements of the vacuum may fluctuate, but the vacuum does not. – John Rennie May 29 '22 at 10:54
  • @Oбжорoв Misinformed about what? About their true existence? Well, that's been argued about endlessly. To no avail. If the math is real then what says the math about them? BTW, maybe it's you who is misinformed but thats not the issue here. – MatterGauge May 29 '22 at 10:55
  • @JohnRennie I have studied qft. And there is a debate on this. Only people who don't actually understand qft (I dont mean you!) the virtual is non-debatable. But again, thats not what I ask. I ask about the math of virtual particles. And dont say "well, you studied it"... ;) – MatterGauge May 29 '22 at 11:05
  • @JohnRennie You write: Measurements of the vacuum may fluctuate, but the vacuum does not Alright then... Measurements of temperature might fluctuate but the temperature doesn''t... ??? – MatterGauge May 29 '22 at 11:14
  • 1
    Temperature is not an eigenvalue of a quantum state. – John Rennie May 29 '22 at 11:16
  • @JohnRennie I you measure the momenta of all particles, you have your T. Dirac deltas are no true eigenvectors but still. My point is though that if your measurements fluctuate, there is a true fluctuation causing it. – MatterGauge May 29 '22 at 11:23
  • @Felicia we can continue this in the Physics SE chat room if you want. The bottom line is that the vacuum state is by definition an energy eigenstate, and energy eigenstates are time independent and therefore cannot fluctuate. – John Rennie May 30 '22 at 09:27
  • @I'll leave one more comment: "It is the integral over the whole four-momentum of the p representation of the Green function of the considered field." – MatterGauge May 30 '22 at 10:31

0 Answers0