New particle turns up in Japan

I'd recommend John Gribbin's Q for Quantum as introduction to the basic terminology and concepts behind contemporary physics. After that, it should be fairly easy to step up to more advanced stuff. Barry Parks and Gordon Kane have written some excellent books which have received surprisingly little attention, even though they do an excellent job at demystfying contemporary particle physics and making it understandable.

I might add that I'm impressed by the level of scientific literacy, and willingess to learn on the part of most layman Freepers-with a few exceptions (*cough*hack*creationists*cough*). Usually, finding mostly laymen discussing on the net means a gathering of crackpots.

You communicate complex ideas in science very well ; now that we know you hung out with Hal Clement, we understand how you learned to do so :-)

Oh, and considering that you frequently find yourself in situations such as this, did you ever think of making this your official smiley?:

I'm not saying that it MATTERS to me that my actions are not really my decision: the illusion of freewill is what is important. We all feel that we have a choice in what we do; that's important to preserve.
As for the counting stuff again: yes; I get it. It is not possible to count every particle in the universe. That does not make my theory wrong, just because it can't be measured.
As to the "causeless" events; do they effect the motion of particles? If they don't, then they would play no role in the unfolding of the universe and my theory would stand up. Otherwise, I will sulk in the corner and ponder my delemma.
Thank you for explaining all of this to a layman. :) Please don't feel that you are beating your head against a wall; I DO understand what you are saying. :) Thanks!

The strong force is proportional to distance, not constant with distance.

I anticipate that there might be some ambiguity in this quote. If we take the Cornell potential for the Quark-Antiquark in QCD it is V = Ar for "large" r (that is greater than 1 fm = 10 to minus 15 m) in addition to this there is a Coulumb term that we can skip here. This leads to quark confinement, since the string tension, A = 0.85 GeV/fm (=1.4kN~ 15 tons!), means that the string will always break and create quark-antiquark pairs if one tries to separate strongly interacting particles. i.e. the quarks are confined.

This is a phenomenological potential and the string part is not, as yet, derivable from the fundamental theory of QCD, although numerical calculations and plausibility arguments suggest that QCD is in agreement with the observations. i.e. the Quark-Antiquark potential is linear for large r (>1fm). Other potentials are as well used to describe this but the Cornell potential seems both to be simple and give good results.

The force is the derivative of the potential, thus the quote should be The strong force potential is proportional to distance and the strong force force is constant.

Thanks for inspiring me to check this.

Here is a nice presentation of QCD: http://www.phys.cmu.edu/halld/talks/morningstar_col_2001.ppt Warning 3.5 MB!

That does not make my theory wrong, just because it can't be measured.

Perhaps not, but it does mean that it's philosophically empty, IMHO. It's like insisting that the universe was created five minutes ago, with all of its apparent "history" built-in. Nobody can disprove that, of course, but that's OK, because it wouldn't change anything if it were true.

Zeno's slave: "But Master! According to your own philosophy, I was fated to steal from you!"

Zeno: "Yes...and I to beat you for it."

As to the "causeless" events; do they effect the motion of particles?

Yes. A decaying atom, for example, will emit particles (an electron, or a gamma ray, or a helium nucleus) that have a definite momentum, and they will collide with particles in their environment.

I'm just a layman, not a professional. But I've always been a hard sci-fi fan. Larry Niven was always one of my favorites.

Same here..Try Hal Clement, very hard science. In one of his books..Mission of Gravity, Whirlgig World, a brief chapter of Mechnical principles were given. :)

The strong force potential is proportional to distance and the strong force force is constant.

I'm afraid neither of these statements is correct.

Yes, that is an approximation. Do you have a better potential?

If you're going to include quark-antiquark pair formation, it will follow the Yukawa potential.

Physicist said: "If you're going to include quark-antiquark pair formation, it will follow the Yukawa potential."

Both gravity and the electromagnetic force obey the inverse-square distance law.

Evidently, the strong force exhibits some other relation.

Quark-antiquark pair formation seems to be the result of adding potential energy to the bond between two quarks by separating them. At some point, the potential energy in the bond is able to be converted into a quark-antiquark pair which then "screens" the original force between the first two quarks, creating two "flux-tubes" in series where previously there was just one. ( I am just parroting back the terminology mentioned above, I don't know what a flux-tube is. I am assuming that it is similar to magnetic "flux" in that it describes the field between the two particles and the word "tube" implies that the field is confined to a region surrounding the line between the two particles.)

Each of the resulting flux-tubes will now behave just like the original flux tube behaved when it was at the smaller spacing of the new flux-tubes.

The quark-antiquark pair formation is a quantum physical event which is outside the scope of my question. My question being "what is the force versus distance law that applies to the original "flux-tube" prior to such quark-antiquark pair formation"?

I will look up the linked article on QCD and see what I can make of it.

Let me lay out the possibilities.

Empirical evidence may exist to suggest that the strong force is not inverse-square. There may be such evidence that the strong force law takes some other mathematical form. There may be evidence that the form of the force law is not a simple algebraic function. It may be that the empirical evidence does not suggest any underlying physical mechanism.

Theoretical "evidence" might exist that the strong force law is not inverse-square. There may be theory which specifies the value at one or two points within the presumed continuous range of the function but without reason to assign any specific function to the relation. There may be competing theories, each of which is consistent with empirical evidence but each of which suggests a different relation for the strong force versus distance. It may be that all of the theories rule out inverse-square law.

My interest in this question is to gain a qualitative sense of the degree to which detailed physical theory has advanced beyond the present state of my knowledge, not necessarily a need to know the specifics. When I went to school the strong force was just described as being "very short range" but I don't think there was much to suggest the mechanism of the force or a mathematical law for it.

One of the interesting facts which I have learned from this thread is that the inverse-square law relation is "special" in that it allows for an "escape velocity" at each point in space such that a particle with a velocity exceeding that will not return to the source of the force. Other force relations may not exhibit this property. Specifically, if the strong force law is such that there is no "escape velocity" then this alone becomes an explanation for why a quark may never be seen in isolation. One might be able to imagine a force law such that the force tends toward infinity as the distance approaches some finite upper limit. Without something like "quark-antiquark pair formation" to complicate things, then one could calculate that it might take all the energy of the universe to move two quarks apart to this upper limit.

Theories concerning whether the universe will continue expanding address the issue of whether there is sufficient mass in the universe to cause the expansion to come to a halt bringing on the "big crunch". Is it the case that the assumption is made that the fastest moving masses in the universe are at the periphery and are moving at near the speed of light away from the center of gravity of the universe. Or, in other words, is the question whether a particle at the periphery of the universe traveling at near the speed of light is above the "escape velocity" which would be calculated knowing the entire mass of the universe and assuming that it is located at the center of gravity of the universe?

Thanks for your help.

My question being "what is the force versus distance law that applies to the original "flux-tube" prior to such quark-antiquark pair formation"?

Again: that force is proportional to distance.

It may be that the empirical evidence does not suggest any underlying physical mechanism.

As I said before, the underlying mechanism is that the gluons that mediate the interaction are themselves drawn together by exchanging gluons. Here is the empirical evidence that gluons exchange gluons. (Point of ego: I am one of the co-authors of that paper.)

When I went to school the strong force was just described as being "very short range" but I don't think there was much to suggest the mechanism of the force or a mathematical law for it.

You are confusing the inter-quark force with the inter-hadron force. The inter-quark force is proportional to distance, and it is what we mean nowadays when we talk about the strong force. The inter-hadron force is very short-range; it is described by the Yukawa potential. It is what people used to mean when they spoke of the strong interaction, but now we know that it is only a secondary, residual force derived from the inter-quark force (i.e., the true strong force) that holds the individual hadrons together.

The mechanism for this force is the exchange of pi-mesons, or pions. Pions are, loosely speaking, quark-antiquark pairs. (You can think of them as representing the quark-antiquark pairs that result from the breaking of the gluon flux tubes.) The short range of the Yukawa force follows directly from the heavy mass of the pion.

Maybe we are talking about different things, but why should the force in the strong force be proportional to distance?

The confinement potential for the quark is often approximated by -4/3*alpha/r + Ar. Thus the force "far away" i.e. longer than 1 fm would be constant.

An interesting derivation of the confinement potential can be found here http://arxiv.org/pdf/nucl-th/9901025 see eq. 9 for the potential.

If we look at the strong force from the quark confinement perspective, the force would be constant.

Physicist said: "Again: that force is proportional to distance."

And AdmSmith said: "The confinement potential for the quark is often approximated by -4/3*alpha/r + Ar. Thus the force "far away" i.e. longer than 1 fm would be constant. "

Thank you both for referring me to relevant articles. Unfortunately, my ignorance is sufficient to keep me from adequately appreciating them. ( Physicist, your link appears to require a subscription.)

AdmSmith is saying that the potential is proportional to distance for larger distances. This would be equivalent to a constant force, I believe. The other term would dominate for smaller distances and would reflect a force law which is the deriviative of the potential and so it would be an inverse-square law for small distances.

Physicist is saying that the force is proportional to distance. This would be similar to stretching a spring. The potential function would then be a square law.

I will have to let you guys duke it out over this. Without further information it sure seems to be that the two claims are contradictory.

I appreciate Physicist pointing out that I was confusing my ancient and simplified description of inter-hadron force (specifically proton-proton) with inter-quark force.

If I understand what you are saying about inter-hadron force, it is that the resultant force is the sum of all the inter-quark forces in a system which will have perhaps a half-dozen quarks in play. But that this resultant will be determined totally by considerations of the inter-quark behavior. Also, that the very short distance of the inter-hadron force is not necessarily a characteristic of inter-quark forces but rather the inter-quark forces are proportional to distance over some relevant distances.

[161]

Thanks for the recommendation and encouragement.

[43] With gluon, muon, lepton, is it going to be called the nip-on?

Great. Sorry for the late response.

If we look at the strong force from the quark confinement perspective, the force would be constant.

You're confusing two things. The confinement potential doesn't describe the force between two quarks; it describes (in its region of applicability, out at the periphery of a hadron) the force between a quark and the hadron in which it is bound. As a description of the force between two quarks, the potential you gave is hopelessly wrong, because it is not asymptotically free.

"Asymptotic freedom" is the name for the experimental result that the strong (i.e. color) force between two quarks goes to zero as the distance between them goes to zero. As you can see, the 1/r term in that confinement potential gives an inverse-square force, which becomes infinte at zero distance.

The best layman's description of confinement potentials can be found in chapter 34 ("Quark Confinement") in The Ideas of Particle Physics by G.D. Coughlan and J.E. Dodd. I also recommend chapter 33, "Asymptotic Freedom".

Hadrons are particles composed of quarks.

That should never be typed by people who tranpsose letters in wodrs. >:)

-Eric

Physicist, your link appears to require a subscription

Whoops! Sorry. I guess I'm reading it from a privileged IP domain. Can you at least see the abstract? The most important point is that the paper makes an experimental measurement of the triple gluon vertex. You can think of this as an event where one gluon absorbs (or emits) another. Photons don't do this: there is no such thing as a triple photon vertex. If there were, electromagnetism would not follow an inverse-square law.

Thanks.