The photon as a mediator particle

In summary: Causality is not violated if I find out that 2+2=4, or that the mass of the sun has a certain value. These facts were true before I was born, and will still be true after I'm dead. Knowing the mass of a black hole is the same way. It doesn't create the possibility of any violation of causality. By conservation of mass-energy, the mass stays the same. It was the same before the black hole collapsed, and it will keep on being the same in the...
  • #1
espen180
834
2
I would like to ask some questions about the photon as a mediator particle of the electromagnetic force.

As far as I know, in order to dertermine the complete state of a photon, we need to know the values of two entities, which are the position and momentum 4-vectors [tex]x^{\mu}[/tex] and [tex]p^{\mu}[/tex]. These are related through the HUP:
[tex]\Delta x^{\mu}\Delta p^{\mu}\geq \frac{\hbar}{2}[/tex] (no summation)
Also, photons always follow geodesic curves in space-time.

However, despite the fact that no geodesics exit from beyond the event horizon of a black hole, charged black holes exert a Lorentz force on other charged bodies. It appears like photons, when mediating the Lorentz force, are exempt from the rules of GR. I see two possibilities:

1. I have misunderstood something fundamental about charged black holes.
2. I don't know enough particle physics to make intelligent guesses about mediator particles.

If anyone could explain the issue to me, I would appreciate it.
 
Physics news on Phys.org
  • #2
i googled and found the following
https://www.physicsforums.com/showthread.php?t=65583
summarizing virtual particles do not obey several properties that normal particles obey, they can travel faster than light, need not be on the mass shell and hence blind to the event horizon.
also this is purely speculation and only a correct theory of QGR can tell us the answer
 
  • #3
Interesting question.

One thing to point out is that what's really forbidden by GR is for *information* to escape from inside the event horizon; if it did, then there would be a local Minkowski frame in which the information was going faster than c, and that leads to a violation of causality.

But the virtual photons coming from a charged black hole don't carry any information. By the no-hair theorem, you can't use them to gain any information about the distribution of charges inside the event horizon, or about the motion of the charges.
 
  • #4
As a "relativist", I have a little problem with speeds and transfers exceeding c. Putting that aside, I would like to raise a point mentioned in the thread Prathyush linked to.

If the photons do not carry no "information" at all, how can they "inform" the outside world about the existence of and amount of charge inside the black hole?
 
  • #5
espen180 said:
As a "relativist", I have a little problem with speeds and transfers exceeding c. Putting that aside, I would like to raise a point mentioned in the thread Prathyush linked to. If the photons do not carry no "information" at all, how can they "inform" the outside world about the existence of and amount of charge inside the black hole?

To carry information, a wave has to be modulated. You can't carry information with just a DC signal (or with an unmodulated sine wave). This is why, for example, you can have phase velocities greater than c.

This is exactly the same issue as the question of how the black hole can inform the outside world of the existence and amount of mass inside the black hole. This is information that was already present, and determinable by outside observers, before the black hole collapsed.
 
Last edited:
  • #6
A very interesting point, was unaware till now.
bcrowell said:
To carry information, a wave has to be modulated. You can't carry information with just a DC signal (or with an unmodulated sine wave). This is why, for example, you can have phase velocities greater than c.

bcrowell said:
This is information that was already present, and determinable by outside observers, before the black hole collapsed.

What do u mean by this? Even a long time after the black hole collapse we can determine the mass of the black hole
 
  • #7
This is information that was already present, and determinable by outside observers, before the black hole collapsed.
Prathyush said:
What do u mean by this? Even a long time after the black hole collapse we can determine the mass of the black hole

Causality is violated if, for instance, I get information about which shirt I'm going to wear tomorrow. If I find out that I'm going to wear the red shirt tomorrow, I can create a paradox by intentionally wearing the blue shirt instead. This type of causality violation occurs in relativity whenever you have a particle with a spacelike world-line. This includes particles like tachyons that move faster than c, and it includes particles escaping through the event horizon of a black hole.

Causality is not violated if I find out that 2+2=4, or that the mass of the sun has a certain value. These facts were true before I was born, and will still be true after I'm dead. Knowing the mass of a black hole is the same way. It doesn't create the possibility of any violation of causality. By conservation of mass-energy, the mass stays the same. It was the same before the black hole collapsed, and it will keep on being the same in the future.
 

Related to The photon as a mediator particle

1. What is a mediator particle?

A mediator particle is a type of subatomic particle that is responsible for mediating the interactions between other particles. It acts as a carrier of forces, allowing particles to interact with each other through the exchange of energy.

2. How does the photon act as a mediator particle?

The photon is the mediator particle of the electromagnetic force. It carries the electromagnetic force between charged particles by exchanging energy with them. This allows for the attraction or repulsion of charged particles, as well as the transmission of light and other electromagnetic waves.

3. Is the photon the only mediator particle?

No, the photon is just one example of a mediator particle. There are other types of mediator particles, such as the W and Z bosons, which are responsible for mediating the weak nuclear force, and the gluon, which mediates the strong nuclear force.

4. How was the photon discovered as a mediator particle?

The existence of the photon as a mediator particle was first theorized by scientists in the late 19th and early 20th century, based on the study of electromagnetism. It was later confirmed through experiments, such as the famous double-slit experiment, which demonstrated the wave-particle duality of light and the role of photons as mediators of the electromagnetic force.

5. What are the implications of the photon as a mediator particle?

The understanding of the photon as a mediator particle has significant implications in the fields of physics and technology. It helps us understand the fundamental forces of nature and has led to advancements in areas such as telecommunications, electronics, and quantum computing. Additionally, the study of mediator particles can also provide insights into the structure and behavior of matter at the subatomic level.

Similar threads

  • High Energy, Nuclear, Particle Physics
Replies
12
Views
2K
  • High Energy, Nuclear, Particle Physics
Replies
13
Views
3K
  • High Energy, Nuclear, Particle Physics
Replies
1
Views
2K
  • Quantum Physics
Replies
3
Views
916
  • High Energy, Nuclear, Particle Physics
Replies
6
Views
2K
  • High Energy, Nuclear, Particle Physics
Replies
4
Views
3K
  • High Energy, Nuclear, Particle Physics
Replies
4
Views
2K
  • Special and General Relativity
Replies
7
Views
386
  • High Energy, Nuclear, Particle Physics
Replies
11
Views
2K
  • Sci-Fi Writing and World Building
Replies
2
Views
1K
Back
Top