- #1
Lepton_vn
- 4
- 0
I have just read a book. It said that: "if symmetry is exact, interaction is a long range". Could you explain me more detailed? Thanks!
Phiphy said:Does it refer to gauge symmetry?
If gauge symmetry is exact, the gauge bosons are massless so interaction is long range; if gauge symmetry is broken, the gauge bosons get mass and interaction becomes short range.
blechman said:that's probably what the book means, although it's wrong! QCD has an "exact" gauge symmetry and yet the force is short-ranged due to confinement. And while we're at it, the phrase "exact symmetries" includes "spontaneously broken" symmetries!
I think your book lied to you!
Please note that the careful assessment released by experimental groups does not claim discovery of a QGP. This seems to contradict at least "naive" expectations dating back to the design of the machines. It therefore not so obvious that your claim holds even in principle.Parlyne said:It is, however, possible to create a quark-gluon plasma (if you're at high enough temperature and pressure)
genneth said:However, I think Phiphy managed to guess the OP's intent --- good work sir :-) For a first level understanding of things, I think it's fairly to say that exact gauge symmetry => massless bosons. It's a useful rule of thumb until you have to face reality
That's right. But i don't understand why if gauge bosons are massless then interaction is long range and vice versa ? Could you explain more clearly? If it is possible, can you prove by using mathematics?Phiphy said:Does it refer to gauge symmetry?
If gauge symmetry is exact, the gauge bosons are massless so interaction is long range; if gauge symmetry is broken, the gauge bosons get mass and interaction becomes short range.
I agree with you in full. I think exact symmetry means when you cannot distinguish the three types of intermediate vector bosons (W+,W-, Z0 particles). They are long range since existing as quarks, they are massless but acquire masses as the symmetry is broken. In this case, they become short range forces. The strong force is an exception as you rightly said since the property of confinement restricts the actions of the glouns making up the quarks. great insightblechman said:that's probably what the book means, although it's wrong! QCD has an "exact" gauge symmetry and yet the force is short-ranged due to confinement. And while we're at it, the phrase "exact symmetries" includes "spontaneously broken" symmetries!
I think your book lied to you!
I think we could make this more logical for him than mathematical. We know that gravity is brought on by the presence of mass and that gravity attracts and thus drops distances a mass is to travel. If we have, let's say, zero mass, there is very little gravitational pullback on the particle and the particle is capable of traveling a relatively longer distance. think you got me.xepma said:The introduction of a mass causes a dropoff of the effective range of the mediated particle. Effectivel, the range drops as ~[tex]e^{-x m}[/tex] (give or take a few parameters). For instance, a massive photon would give rise to a modified Coulomb potential that looks like: [tex]\frac{1}{r}e^{-x m}[/tex]. For m=0, the exponential dropoff vanishes and we have long-ranged behavior again.
Here we are not discussing the color force's broken symmetry. In fact there's no way to achieve such high temperatures. Put simply, because the gluons are contained in the neutron and proton. they cannot be used to predict the range. anything coming out of the neutron or proton will be a quark-antiquark pair and we could presume that since the pion is the lightest possible meson, it's possible to use them for range calculation. the range of the gluon is indeed short (it is considered the acrrier of the strong force).Parlyne said:I think you need to be little more careful here. It's certainly true that the force between nucleons is short-ranged. However, nucleons have 0 charge under the strong force. Using nucleons to judge the range of a force is like saying the electromagnetic force is short-ranged because atoms have to be close to each other to feel such forces. What matters is the range of the force which acts on the quarks making up nucleons; and, this is a much subtler question.
It is, however, possible to create a quark-gluon plasma (if you're at high enough temperature and pressure), in which quarks no longer remain bound. Since there's no confinement here, it should be much clearer that the strong force is, in fact, long-ranged.
Abbas Sherif said:Here we are not discussing the color force's broken symmetry. In fact there's no way to achieve such high temperatures. Put simply, because the gluons are contained in the neutron and proton. they cannot be used to predict the range. anything coming out of the neutron or proton will be a quark-antiquark pair and we could presume that since the pion is the lightest possible meson, it's possible to use them for range calculation. the range of the gluon is indeed short (it is considered the acrrier of the strong force).
Symmetry in the context of interactions refers to the balance or correspondence between the properties of two interacting objects or systems. This can include properties such as shape, size, orientation, and motion.
The symmetry between two objects can affect the range of interaction between them, as it determines the strength and type of force that they exert on each other. Objects with more symmetry may have a longer range of interaction, while those with less symmetry may have a shorter range.
There are several types of symmetries that can influence interactions, including rotational symmetry, translational symmetry, and reflection symmetry. These symmetries can be present in different forms, such as mirror symmetry, rotational symmetry around a specific axis, or translational symmetry along a specific direction.
Yes, symmetries can exist in electromagnetic interactions. For example, the laws of electromagnetism exhibit symmetry under both time reversal and charge conjugation. This means that the laws are the same whether time is moving forward or backward, and whether particles are replaced with their antiparticles.
Scientists use various experimental methods, such as particle accelerators and detectors, to study the symmetries and range of interaction between particles. They also use theoretical models and calculations, such as quantum field theory, to understand and predict these interactions based on the symmetries present.