Debunking the Existence and Duration of Virtual Particles

[byron178]

Don't virtual particles time travel backwards?

 

[haushofer]

Don't virtual particles time travel backwards?

Why would they?

 

[Lapidus]

Well first of all Isaac Asimov certainly was not a "heavy-weight" of physics, he wasn't even a physicist.

Wilczek, t'Hooft, Randall, Kane certainly are.

Virtual particles are a calculational tool, not reality, they're a way we can mathematically get the answer we want to arbitrary accuracy, they're not new physics.

How are we to explain static electric and magnetic fields if virtual photons are just a mathematical artifact?

 

[tiny-tim]

hi byron178!

Don't virtual particles time travel backwards?

i think you're thinking of anti-matter …

eg an electron going forward in time behaves exactly the same as a positron going backward in time, both in Feynman diagrams and in the equations

(and a creation operator for an electron behaves like an annihilation operator for a positron, and vice versa)

 

[danR]

Well first of all Isaac Asimov certainly was not a "heavy-weight" of physics, he wasn't even a physicist. He was a bio-chemist and a science fiction writer. Also, virtual particles are not needed to explain the Casimir effect. Essentially the issue is something like this. ...

...Virtual particles are a calculational tool, not reality, they're a way we can mathematically get the answer we want to arbitrary accuracy, they're not new physics.

I know all about Asimov: he was a popularizer; my point was that Asimov's popular explanation differs little from the Harvard heavyweight's one. It seems to be a good-enough defense for real-particle status. Both the Harvard woman, and the SA writer are experts in the field, and the latter specifically addresses the 'are they just a mathematical bookkeeping device?' He says resoundingly NO! They are real particles. I'm just not happy with his casual Casimir defense, but I'm confident that he is sufficiently familiar with the literature to know whether or not the mathematical-artifact arguments are sufficient to the evidence. If anyone presumes to speak ex cathedra on the non-real existence of VP, I'm sure they will be happy to debate the weighty proponents publicly.

Don't lose my real point. It's not whether you are right or wrong, it's the credentials of experts in the field who appear to be comfortable with VP-real. I have to pay attention to their weight, and compare it with that of the critics.

Someone in a post stated they did actually poll the experts in an email, but whether the responses should be published here seemed to be an issue.

But from what I see of expert opinions, VP-real seems to be an OK position

 

[danR]

Wilczek, t'Hooft, Randall, Kane certainly are.

Yes, my point was that Randall hardly differed from Asimov in the surface form of her popularized argument. I know very well Asimov was a popularizer. In his day most would not have called him a scientist, even a biochemical scientist.

I have the feeling that the above experts would know a thing or two about the 'math-artifact' arguments, and would be able to counter them. If they have countered them in print, then some research is in order by critics to pull some of that print into physics forums and disassemble them.

 

[Polyrhythmic]

Yes, my point was that Randall hardly differed from Asimov in the surface form of her popularized argument. I know very well Asimov was a popularizer. In his day most would not have called him a scientist, even a biochemical scientist.

I have the feeling that the above experts would know a thing or two about the 'math-artifact' arguments, and would be able to counter them. If they have countered them in print, then some research is in order by critics to pull some of that print into physics forums and disassemble them.

I honestly have no idea why those experts would advocate the reality of virtual particles, other than maybe just because it seems like a beautiful explanation. Particles buzzing back and forth. Neat.
But still, the concept of logical reasoning is clearly against the concept of virtual particles, as shown by countless arguments in this thread.

 

[Lapidus]

virtual particles are talked about only in perturbation theory

"a particle that does not obey E² - p².c² = m².c⁴ for a time allowed by the energy-time uncertainty relation" is just science fiction writing, much like "a spaceship that goes faster than light", or "Heisenberg compensators" … you can't just string words together, you need to be able to insert the idea into a theory

Check out science fiction by Leonard Susskind, starting around min 43 till around min 74.

http://www.youtube.com/watch?v=5rytN74EOi0&feature=player_embedded#at=3359

I think, he is very clear that it is an interpretational issue.

 

[byron178]

hi byron178!


i think you're thinking of anti-matter …

eg an electron going forward in time behaves exactly the same as a positron going backward in time, both in Feynman diagrams and in the equations

(and a creation operator for an electron behaves like an annihilation operator for a positron, and vice versa)

Does that mean they really travel backwards?i was asking if they can travel backwards in time because they can travel faster than light,they become space-like.

 

[Polyrhythmic]

Does that mean they really travel backwards?i was asking if they can travel backwards in time because they can travel faster than light,they become space-like.

That's a matter of interpretation, but I'd rather stick with the forward-in-time one. They don't travel faster than light.

 

[maverick_starstrider]

Does that mean they really travel backwards?i was asking if they can travel backwards in time because they can travel faster than light,they become space-like.

It's ultimately an issue of an extra minus sign floating around. You can tuck it into the velocity and say it's moving backwards or you can tuck it into the charge and say it behaves like an electron in every way except it has the opposite charge. It's conceptually much simpler to just tuck it in with the charge.

 

[tiny-tim]

Does that mean they really travel backwards?i was asking if they can travel backwards in time because they can travel faster than light,they become space-like.

no, anti-matter travels slower than light, just like matter (but, as i said, it behaves like matter at the same speed but going backwards in time)

also, motion faster than light (in other words, space-like motion) would not involve going backward in time …

this is a science fiction error, caused by saying that since time dilation of √(1 - (v/c)²) goes from 1 to 0 as v approaches c, that means it must become negative if v > c … and that obviously isn't true! ​

 

[maverick_starstrider]

no, anti-matter travels slower than light, just like matter (but, as i said, it behaves like matter at the same speed but going backwards in time)

also, motion faster than light (in other words, space-like motion) would not involve going backward in time …

this is a science fiction error, caused by saying that since time dilation of √(1 - (v/c)²) goes from 1 to 0 as v approaches c, that means it must become negative if v > c … and that obviously isn't true! ​

Yes, the energy of a particle going faster than the speed of light is actually complex (i.e. has an imaginary component, i.e. a+bi). What could a complex energy possibly mean? Well luckily there's no evidence for the existence of such particles so we don't really have to attempt to make any sense out of such a mind bogglingly out there concept.

 

[maverick_starstrider]

BTW, If you want to talk about heavy-hitters and there opinions here's a lecture I was just watching by Anthony Zee (of "Quantum Field Theory in a Nutshell" fame)

http://v.youku.com/v_show/id_XMTE0OTI4Nzg0.html

Check around the 45 minute mark. He goes on to talk about how the concept of Feynman Diagrams (i.e. virtual particles) "shackled" the study of QFT for quite some time. it wasn't until people like t'Hooft pointed out that there exist phenomena (such as magnetic monopoles) that CANNOT be described through the perturbative framework that virtual particles represent, that QFT began to free itself from the "shackles of Feynman Diagrams". Putting words in his mouth a bit he's basically saying that not only are these perturbation not real things but for a 30 year stretch or so they were blinding people to the real physics by taking these things too seriously.

 

[byron178]

no, anti-matter travels slower than light, just like matter (but, as i said, it behaves like matter at the same speed but going backwards in time)

also, motion faster than light (in other words, space-like motion) would not involve going backward in time …

this is a science fiction error, caused by saying that since time dilation of √(1 - (v/c)²) goes from 1 to 0 as v approaches c, that means it must become negative if v > c … and that obviously isn't true! ​

there is this article i found that say's they do time travel backwards in time. http://www.desy.de/user/projects/Physics/Quantum/virtual_particles.html

 

[maverick_starstrider]

there is this article i found that say's they do time travel backwards in time. http://www.desy.de/user/projects/Physics/Quantum/virtual_particles.html

That's what he said. Going backwards in time and going faster than light are entirely different things. Whether you're going backwards down a one way street in a car or whether your car is going over 100 miles per hour have nothing to do with each other. Mathematically there is no difference between saying that anti-particles are particles with the same charge moving backwards in time or particles with opposite charge moving forward in time. In neither case is it being suggested that they are moving FASTER than the speed of light.

 

[tiny-tim]

there is this article i found that say's they do time travel backwards in time. http://www.desy.de/user/projects/Physics/Quantum/virtual_particles.html

but that has nothing to do with moving faster than light …

it's just the example i mentioned earlier, of an anti-particle behaving like a particle going backward in time (in this case, a photon, which of course is its own anti-particle)

 

[tiny-tim]

Lapidus, i claim that Susskind suppports me! … Susskind specifically says that virtual particles are mathematical constructs, that virtual particles popping into existence are a "picture", and gives an example of an electron containing a hydrogen atom that seems clearly intended to rubbish the idea …

Check out science fiction by Leonard Susskind, starting around min 43 till around min 74.

(that's Lecture 6 (February 15, 2010) of Susskind's Stanford University course "New Revolutions in Particle Physics: The Standard Model")

at 0:55 he is asked "exactly what is the difference between a real and a virtual particle?", and he says

"virtual particles are mathematical constructs which are the internal particles in a Feynman diagram"​

(he then goes on to describe how if they existed we wouldn't be able to detect them, but i hope you're not claiming that proving that they're undetectable somehow proves that they exist?! )

later, he mentions the picture of a proton continually oscillating into a W plus a neutron and back again, so that an energetic enough photon can knock the W out, leaving the neutron, and someone asks him (around 1:03) whether that means the W was already there, and he replies

"your mental picture that whatever comes out of a system was in there beforehand is a little bit defective!"​

I think, he is very clear that it is an interpretational issue.

what does that mean?

Susskind says that the existence of a virtual W is a "picture", and he then goes on to show how absurd the picture is

the only unequivocal thing he says is (at the very start) that "virtual particles are mathematical constructs"

 

[byron178]

but that has nothing to do with moving faster than light …

it's just the example i mentioned earlier, of an anti-particle behaving like a particle going backward in time (in this case, a photon, which of course is its own anti-particle)

but they don't really travel backwards in time,right?

 

[tiny-tim]

but they don't really travel backwards in time,right?

right!

 

[byron178]

right!

are you guys arguing as to if virtual particles exist? i keep reading different respones and have read different articles one by gordon kane where he claims they are real. http://www.scientificamerican.com/article.cfm?id=are-virtual-particles-rea

 

[Polyrhythmic]

are you guys arguing as to if virtual particles exist? i keep reading different respones and have read different articles one by gordon kane where he claims they are real. http://www.scientificamerican.com/article.cfm?id=are-virtual-particles-rea

Yes, this thread is about the reality of virtual particles. That article was already posted, and it is flawed.

 

[maxverywell]

so that an energetic enough photon can knock the W out, leaving the neutron, and someone asks him (around 1:03) whether that means the W was already there, and he replies

"your mental picture that whatever comes out of a system was in there beforehand is a little bit defective!"​

But it means that before you knock out the W, there was "something" and that "something" somehow become a real W boson. This "something" is actually what we call virtual W and it's a matter of how you define things in physics.

the only unequivocal thing he says is (at the very start) that "virtual particles are mathematical constructs"

I think he means that virtual particles are described by mathematics (at the way they are described in perturbation theory).

 

[byron178]

But it means that before you knock out the W, there was "something" and that "something" somehow become a real W boson. This "something" is actually what we call virtual W and it's a matter of how you define things in physics.




I think he means that virtual particles are described by mathematics (at the way they are described in perturbation theory).

are you saying virtual particles exist?

 

[Polyrhythmic]

But it means that before you knock out the W, there was "something" and that "something" somehow become a real W boson. This "something" is actually what we call virtual W and it's a matter of how you define things in physics.

That's not what he said. At first he states that it is a mathematical construct. Later he goes on to explain that even if it was really there, it wouldn't be detectable because we couldn't distinguish the detection from the creation of an actual particle.

 

[byron178]

That's not what he said. At first he states that it is a mathematical construct. Later he goes on to explain that even if it was really there, it wouldn't be detectable because we couldn't distinguish the detection from the creation of an actual virtual particle.

So even if they were real we would not be able to detect them?

 

[maverick_starstrider]

So even if they were real we would not be able to detect them?

By definition. However, I'm afraid we've high-jacked the thread from you. You'll never really be able to get a handle on what the issue we're discussing is without actually knowing physics. SciAm and science popularizer books essentially throw out damn near everything important to relate things in an "intuitive" analogy with the real world.

As for the rest of you guys, I'd re-iterate that feynman diagrams (and thus a virtual particle picture of QFT) MISS certain physics. I don't see how this doesn't seal the issue. We have an integral, we want to perform a functional integration on it. We can't, so we move to a perturbation approach, from this comes the calculational TOOL of virtual particles. Because we're working perturbatively we miss certain things (which essentially means such things are unexplainable via virtual particles). From this we conclude that virtual particles are real physics?! Where do we go next? When we don't know the ground state of the system so we try a trial wave-function parameterized by some variable lambda (i.e. a variational approach) and we minimize with respect to lambda and call the lowest state the ground-state. We then find out that our ground-state wasn't of the form we guessed but we were kind of close. From this you're saying we conclude that our variational lambda is a REAL degree of freedom of the system? If I have 3 apples do I really have 6 apples plus 3 negative-apples?

 

[byron178]

By definition. However, I'm afraid we've high-jacked the thread from you. You'll never really be able to get a handle on what the issue we're discussing is without actually knowing physics. SciAm and science popularizer books essentially throw out damn near everything important to relate things in an "intuitive" analogy with the real world.

As for the rest of you guys, I'd re-iterate that feynman diagrams (and thus a virtual particle picture of QFT) MISS certain physics. I don't see how this doesn't seal the issue. We have an integral, we want to perform a functional integration on it. We can't, so we move to a perturbation approach, from this comes the calculational TOOL of virtual particles. Because we're working perturbatively we miss certain things (which essentially means such things are unexplainable via virtual particles). From this we conclude that virtual particles are real physics?! Where do we go next? When we don't know the ground state of the system so we try a trial wave-function parameterized by some variable lambda (i.e. a variational approach) and we minimize with respect to lambda and call the lowest state the ground-state. We then find out that our ground-state wasn't of the form we guessed but we were kind of close. From this you're saying we conclude that our variational lambda is a REAL degree of freedom of the system? If I have 3 apples do I really have 6 apples plus 3 negative-apples?

that's ok,what i want to know is when something travels faster than light will it start traveling backwards in time?will it travel for example today to yesterday?

 

[muppet]

BTW, If you want to talk about heavy-hitters and there opinions here's a lecture I was just watching by Anthony Zee (of "Quantum Field Theory in a Nutshell" fame)

http://v.youku.com/v_show/id_XMTE0OTI4Nzg0.html

Check around the 45 minute mark. He goes on to talk about how the concept of Feynman Diagrams (i.e. virtual particles) "shackled" the study of QFT for quite some time. it wasn't until people like t'Hooft pointed out that there exist phenomena (such as magnetic monopoles) that CANNOT be described through the perturbative framework that virtual particles represent, that QFT began to free itself from the "shackles of Feynman Diagrams". Putting words in his mouth a bit he's basically saying that not only are these perturbation not real things but for a 30 year stretch or so they were blinding people to the real physics by taking these things too seriously.

It's interesting to hear that t'Hooft said that. I had a quick look at Veltmann's QFT text the other day and he seemed to argue the the old-fashioned view that QFT is essentially a tool for deriving Feynman rules in the absence of a better alternative!

Regarding popularising science: when I explain what my PhD is on to people who know nothing about physics, I'll tell them that the modern understanding of forces between two interacting objects involves particles being exchanged between them. I usually won't tell them that any real physical system that bears any relation to what we think of as a particle exists only to the extent that interactions can be neglected. Popular accounts mean nothing.

 

[Polyrhythmic]

that's ok,what i want to know is when something travels faster than light will it start traveling backwards in time?will it travel for example today to yesterday?

Nothing can travel faster than light, our theoretical framework does not permit such a process. Therefore the best answer would be "no".

 

[byron178]

does quantum entanglement allow information to travel faster than light? http://en.wikipedia.org/wiki/Faster-than-light scroll down to quantum mechanics

 

[Born2bwire]

does quantum entanglement allow information to travel faster than light? http://en.wikipedia.org/wiki/Faster-than-light scroll down to quantum mechanics

No, it does not.

 

[dm4b]

As for the rest of you guys, I'd re-iterate that feynman diagrams (and thus a virtual particle picture of QFT) MISS certain physics. I don't see how this doesn't seal the issue. We have an integral, we want to perform a functional integration on it. We can't, so we move to a perturbation approach, from this comes the calculational TOOL of virtual particles. Because we're working perturbatively we miss certain things (which essentially means such things are unexplainable via virtual particles). From this we conclude that virtual particles are real physics?! Where do we go next? When we don't know the ground state of the system so we try a trial wave-function parameterized by some variable lambda (i.e. a variational approach) and we minimize with respect to lambda and call the lowest state the ground-state. We then find out that our ground-state wasn't of the form we guessed but we were kind of close. From this you're saying we conclude that our variational lambda is a REAL degree of freedom of the system? If I have 3 apples do I really have 6 apples plus 3 negative-apples?

These were excellent points. But, a problem still remains.

You don't often here people claiming that the variational lambda is a REAL degree of freedom of the system. Nor, do you hear people talking as if negative-apples exist in reality.

But, you always see physicists speaking (perhaps colloquially), as if virtual particles do in fact exist.

Also, there seems to be a lack of consensus on whether or not virtual particles are "real" amongst the top minds in physics, as was evident on another PF thread. The same can't be said about "negative-apples".

Not too long ago, I posted a recent example of this dealing with the dynamic casimir effect:

https://www.physicsforums.com/showthread.php?t=503456

If virtual particles are indeed NOT real, none of this is helping matters

 

[dm4b]

No, it does not.

No doubt, we cannot send a signal faster than light utilizing entangled particles. Nature prevents that from happening.

BUT, how do we explain the apparent "instantaneous" connection between the two entangled particles?

It almost appears that some sort of "information" has traveled between the two, during a measurement. After all, a connection implies some type of information transfer.

 

[Goldstone1]

ive been reading on this forum that virtual particles flat out don't exist?then why is it said they exist for a certain amount of time?

Virtual particles are real, they just exist for very short periods of time. It's a myth really to say virtual particles aren't really real, as they do contribute to real things in the outside world, such as the stability of a Hydrogen Atom.