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Quantum Physics question

daenku32

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Since it's so easy subject.

Can a particle and anti-particle only appear FROM a boson? Or can they appear in true vacuum? If so, considering that the annihilation of the particle and anti-particle causes energy release in the form of a boson, doesn't that mean energy was created out of "nothing"?

I'm sure this is wrong, even though I personally would consider the particle/anti-particle tango to explain dark matter and maybe even accelerating expansion of universe.
 
particle and anti-particle can appear in a true vacuum. They can be created out of nothing.

That isn't wrong.. that is how it is.

But these particles don't last long, the heavier the particle being created like that, the shorter time it will live and the less often it will be created.

But it does just happen.
 
TobiasTheCommie said:
particle and anti-particle can appear in a true vacuum. They can be created out of nothing.

That isn't wrong.. that is how it is.

But these particles don't last long, the heavier the particle being created like that, the shorter time it will live and the less often it will be created.

But it does just happen.
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But doesn't the annihilation of the particle and anti-particle release energy? This energy would result in net increase of total energy if there was none to start with.
http://physics.bu.edu/atlas/guide/anti-matter.html
 
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as i understand it there is a net decrease of total energy(from the creation of the particle and the anti-particle) untill the particle and anti-particle are annihilated and create energery leaving the end result at 0.

But i ain't a physicist, so can't explain the details.
 
I can say that I use quantum boson batteries in my condom demagnetizer/remote viewer blockers. They last a long time.
 
According to this Wiki link, you need a boson.

http://en.wikipedia.org/wiki/Pair_creation

Pair production refers to the creation of an elementary particle and its antiparticle, usually from a photon (or another neutral boson). This is allowed, provided there is enough energy available to create the pair – at least the total rest mass energy of the two particles – and that the situation allows both energy and momentum to be conserved (though not necessarily on shell). All other conserved quantum numbers (angular momentum, electric charge) of the produced particles must sum to zero — thus the created particles shall have opposite values of each (for instance, if one particle has strangeness +1 then another one must have strangeness −1).
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You need a boson. There must be a source of the energy to start with. The pair is spontaneously created from this energy source, then upon destruction generally returns to being the initial boson. The most important thing is that there is conservation of energy. No energy created or destroyed.

The reason this occurs in a vacuum is that a vacuum is full of neutral particles such as neutrinos and photons.
 
daenku32 said:
Since it's so easy subject.

Can a particle and anti-particle only appear FROM a boson? Or can they appear in true vacuum? If so, considering that the annihilation of the particle and anti-particle causes energy release in the form of a boson, doesn't that mean energy was created out of "nothing"?

I'm sure this is wrong, even though I personally would consider the particle/anti-particle tango to explain dark matter and maybe even accelerating expansion of universe.
Click to expand...
Nothing comes from nothing, even in quantum physics. :)

I think you may be confusing the production of pairs of virtual particles from a "pure" vacuum and the production of pairs of real particles from an energy source.

Have a look at this random link.

Now let's look at the vacuum. Suppose that there is nothing in the vacuum (no matter or radiation at all), according to the HUP (Heisenberg Uncertainty Principle...DD) there is an uncertainty in the amount of energy which can be contained in the vacuum. On average, the energy is constant, however, there is always a slight uncertainty in the energy, dE. This small uncertainty allows a nonzero energy to exist for short intervals of time defined by

dT = (h/2pi) / dE

Small uncertainties in energy can actually live for very long times. Because of the equivalence between matter and energy, these small energy fluctuations can produce matter (particles) which exists for a short time and then disappears.

The particles produced in this manner are not arbitary. What happens is that pairs of particles are produced -- a particle and its anti-particle twin are produced. This allows certain properties of the Universe to be preserved. Also, an interesting note is that the particles cannot be measured directly (hence the name virtual pairs) and so no physical laws such as the conservation of energy are seen to be violated!
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If you want to get way into this, there is actually experimental proof that the average energy of empty vacuum is not zero. A guy named Casimir realized that the Heisenberg Uncertainty Principle implied this was so, and constructed a device out of two plates that he could move very close together so that he could exclude longer wavelengths of this "vacuum energy" or "zero point energy" and therefore create a piece of vacuum between the plates that would be lacking some of the zero point energy. He theorized that if this were correct, the plates would be forced together by the pressure of the vacuum energy surrounding them, and he calculated how much. He demonstrated the effect, and his measurements were in line with his calculations. The effect is called the "Casimir effect" in his honor.

So when you start to think that this is just some sort of bookkeeping thing, or something the physicists just made up, please be aware that this effect must be explained, and the vacuum energy does so very neatly. It's not just something they made up. It actually exists and we can measure it.
 
You do not need anything, spontaneous pair production can happen in a true vacuum. This is an example of one of the uncertainty principles, that of time and energy. According to this E*t < h (E = energy, t = time, h = Placnk's constant). As long as the particles exist only for a short time there is no reason this cannot happen, and as Schneibster says, the Casimir effect is a very neat demonstration that it does.

Also, I'm not sure why you are talking about bosons. There are two different ways of classifying particles. The first is based on fundamental particles and is made up of hadrons, such as protons, which contain quarks, and leptons, which are not made of anything (that we know of), such as electrons. The other way of classifying them is as bosons or fermions. This is based on a particle's angular momentum, or spin. A fermion has half-integer spin, that is it's spin is always h*(2n-1)/2, while a boson has integer spin, h*n. All the fundamental particles (quarks and leptons) are fermions, while the force carriers (photons, gluons, etc.) are, so far, all bosons (although the graviton might confuse things if it exists). This is farily simple for fundamental particles, but it also applies to all other particles. For example, a deuterium nucleus is a boson while a tritium nucleus is a fermion. During pair production, any particles can be created (depending on the conditions), so it makes no sense to talk exclusively of bosons.
 
This sounds related to Stephen Hawkings ideas about pair production at the boudary of black holes and how, over time, black wholes evaporate away.

Could anybody tie the two ideas together or explain how they aren't related?
 
They are related because they involve pair production, near a black hole there are three options: they both cross the event horizon, one does not cross the event horizon, neither crosses the event horizon. In the middle case there is the 'creation' of a particle because the anti partocle can no longer anihilate it's quantum mate.

If the 'new' matter comes out of the mass/energy of the black hole or the vacum energy, I have no idea.
 
Dancing David said:
They are related because they involve pair production, near a black hole there are three options: they both cross the event horizon, one does not cross the event horizon, neither crosses the event horizon. In the middle case there is the 'creation' of a particle because the anti partocle can no longer anihilate it's quantum mate.

If the 'new' matter comes out of the mass/energy of the black hole or the vacum energy, I have no idea.
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It comes out of the black hole, which is why it evaporates. To put it simply, the event horizon can be assumed to be the "edge" of the black hole. When a pair is produced exactly on the edge, one particle can travel inside the hole while the other travels away. To an external observer all that is seen is a particle being emitted from the surface of the black hole, which is really no different from a particle being emitted from any other object - the black hole loses the mass of that particle.
 
Cuddles said:
You do not need anything, spontaneous pair production can happen in a true vacuum. This is an example of one of the uncertainty principles, that of time and energy. According to this E*t < h (E = energy, t = time, h = Placnk's constant). As long as the particles exist only for a short time there is no reason this cannot happen, and as Schneibster says, the Casimir effect is a very neat demonstration that it does.

Also, I'm not sure why you are talking about bosons. There are two different ways of classifying particles. The first is based on fundamental particles and is made up of hadrons, such as protons, which contain quarks, and leptons, which are not made of anything (that we know of), such as electrons. The other way of classifying them is as bosons or fermions. This is based on a particle's angular momentum, or spin. A fermion has half-integer spin, that is it's spin is always h*(2n-1)/2, while a boson has integer spin, h*n. All the fundamental particles (quarks and leptons) are fermions, while the force carriers (photons, gluons, etc.) are, so far, all bosons (although the graviton might confuse things if it exists). This is farily simple for fundamental particles, but it also applies to all other particles. For example, a deuterium nucleus is a boson while a tritium nucleus is a fermion. During pair production, any particles can be created (depending on the conditions), so it makes no sense to talk exclusively of bosons.
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I mentioned bosons since I've seen examples of a boson 'transforming' into a short lived particle pair that then recreates the boson at the end of the pair life (during annihilation). So the boson would be the energy, and the pair would be the matter.
 
Cuddles said:
It comes out of the black hole, which is why it evaporates. To put it simply, the event horizon can be assumed to be the "edge" of the black hole. When a pair is produced exactly on the edge, one particle can travel inside the hole while the other travels away. To an external observer all that is seen is a particle being emitted from the surface of the black hole, which is really no different from a particle being emitted from any other object - the black hole loses the mass of that particle.
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I do understand hawking's idea, I remeber learning about it is the 79s or something like that.

What I am sayin however is that i am not usre where the energy for the particle production actauly comes from, since there are a number of possibilities and I don't know what recent theories are.

The particle pair could be created from just the energy of space time and therefore while the particles appear close to the event horizon, one of them falls into the black hole and the other doesn't therefore the net change in the black holes mass actualy increases.
The particles are created from the energy of the black hole and therefore there is a net loss of the mass of the black hole.
I understand that the first possibility could actualy be the same as the second, if the expression of space time is the sole determinant of the particle production and I know that black holes are still in space time.

But I am a concrete thinker, so while I understand the general idea of hawking's evaporation, I don't know what other data supports the theory.

So I am just not sure what reaserch has shown about the theory because I don't know what it recently has been discussed.
 
time and energy

There are some points you might want to consider.
1st, the status of _a_ time-energy indeterminacy relation is rather involved. If you are good in maths and familiar with functional analysis, I'd suggest Paul Busch's chapter in "Time in Quantum Mechanics", published by Springer (Disclaimer: I am one of the editors - it is currently out of print, a new edition coming soon).
If not, you should at least understand that there is a wealth of time-energy indeterminacy relations, for the very simple fact that what "time" means depends on the question you are actually posing: How much "time" is spent in a room? At what "time" did you arrive? The first concerns a _duration_ whereas the other concerns an _instant_, for example (spare me the discussion about the duration being determined by two instants or the instant being actually measured by duration, both of which are true - but they are different beasts mathematically, and, in particular, there is no time-energy uncertainty relation with the first one).

The particle pair production ex vacuo mentioned above can only take place in the context of quantum _fields_, and there is no breakdown of energy conservation at all there: virtual pairs are quantum fluctuations of the field compatible with hamiltonian flow.

However, the qualitative discussion of pair production in the vicinity of the event horizon is very useful for a first understanding of black hole thermodynamics.

2nd, Particle - antiparticle (real) pairs: a particle and its antiparticle are both either bosons or fermions. So the total angular momentum of the pair will be entire. So, only from a boson (subject to the usual kinematic constraints).

3d, it has indeed been argued that the cosmological constant is due to vacuum energy. I still have to read a fully developed theory, however....

Have fun!
 
Cuddles said:
It comes out of the black hole, which is why it evaporates. To put it simply, the event horizon can be assumed to be the "edge" of the black hole. When a pair is produced exactly on the edge, one particle can travel inside the hole while the other travels away. To an external observer all that is seen is a particle being emitted from the surface of the black hole, which is really no different from a particle being emitted from any other object - the black hole loses the mass of that particle.
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This is what I don't understand.

Who cares what en external observer sees? The particle DIDN'T come from the black hole, therefore the black hole can't lose energy.

I know I'm wrong, 'cause Hawking is right, but HOW am I wrong :confused:
 
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