Nuclear force/inverse xth power law

[granpa]

some have suggested that gravity can be unified with the nuclear force by introducing extra dimensions so that gravity doesn't follow an inverse square law at short distances. it seems like it should be rather easy to determine whether the nuclear force follows an inverse cube or 4th or 5th power law yet I have never heard anything about it.

 

[arivero]

Indeed, the searches are in progress. I believe they have already fitted the usual low for distances as small as 0.01 millimeters or so. It is not "easy", it is "tabletop".

 

[granpa]

usual low? are you talking about gravity or the nuclear force? my question was about the latter.

 

[malawi_glenn]

The nucleon-nucleon force is more than just a simple central, radial dependent potential.

Also, who are 'some' which you are referring to in your first post?

 

[granpa]

I can't believe you haven't heard of this theory. google turns up plenty of hits. here is just 1.

http://www.eurekalert.org/features/doe/2001-10/dbnl-gil053102.php

 

[malawi_glenn]

I have heard about that, string theory is very popular. But what have that to do with the Nuclear Force?

Which force are you referring to? The Strong (colour) force, or the Nuclear force (force between hadrons)?

 

[granpa]

apparently you haven't heard of it. the idea is that the nuclear force follows an inverse 4th, 5th, or 6th power law up to a certain distance then follows a regular inverse square law from there on. the reason being that there exists, according to the theory, extra dimensions that are shorter than that distance.

 

[malawi_glenn]

I have heard of string theory, and have worked a lot on the Nucleon-Nucleon force, therefor I ask you what kind of "Nuclear Force" you are referring to.

Do you have an article or similar that cover this, Iam interessted since I am into Hadron Physics.

 

[humanino]

the idea is that the nuclear force follows an inverse 4th, 5th, or 6th power law up to a certain distance then follows a regular inverse square law from there on.

That's wrong. Where did you get that from ?

 

[malawi_glenn]

That's wrong. Where did you get that from ?

That is what I am wondering too ..

 

[granpa]

I am not an expert. I am looking for the same answers you are. like I said, google turns up plenty of hits.

here is a thought. if the nucleons attract each other with an inverse nth power law because they exist in an n+1 dimensional space then if each gets spread out uniformly over a large area due to the uncertainty principle, the resulting attraction below that range should increase with increasing distance between them, just like the strong force.

 

[malawi_glenn]

But have you studied the nucleon-nucleon force? There is like 7 components or so... its not a 'simple' inverse power law function... if you have done the googleing, why can't you atleast cite and write down your sources? maybe you have missunderstood something in the articles which you read?

 

[granpa]

I am finding it hard to believe that none of you have heard of this. I hove already linked to 1 page. this is not a personal theory that I am advocating. there is research currently going on and I am simply asking for information about it. you are asking me for exactly what I am asking for.

I have already said that I am not an expert.

 

[malawi_glenn]

But in your first post and in post #7, you are referring to stuff that is not covered in the article you are linking to in post #5.

I have never heard anyone trying to descrice the centra, radial part of the nucleon-nucleon force with an inverse power law... nor less about the pecularites that you are adressing to it.

So maybe you have either read totally non-sense articles, or missunderstood the articles, hence me and Humanino are asking where you have encountered the information that you are stating in post #1 and post #7.

 

[humanino]

I hove already linked to 1 page.

The link you provided directed me to a page which does not even contain the word "nuclear". The nuclear force must be modeled by something more complicated than mere power laws as a function of distance. There is no escape from that. If somebody is trying to do that, then he must modify what we call distance. Therefore, I can not disregard your claims as trivially wrong, because you are referring to string theory which does modify our concepts of distances. I however find it extremely unlikely that one could do so in any reasonable manner to describe nuclear forces comparably to what is already known.

Once again, can you point us to a reference which says that nuclear forces are described by mere power laws, modified by extradimensions, in a string unification scheme ?

 

[Vanadium 50]

Once again, can you point us to a reference which says that nuclear forces are described by mere power laws, modified by extradimensions, in a string unification scheme ?

He can't show us one, because there can't be one.

Power laws are positive definite. The nuclear force changes sign: it's repulsive at short range and attractive at long range. So no remapping between them will work.

 

[granpa]

from the link:

How big would extra dimensions have to be? For gravity to equal the other forces at a hundred-thousandth of a trillionth of an inch (the electroweak scale), one extra dimension would have to be as big as the distance between the Earth and the sun. Two extra dimensions need extend only about a millimeter, however, and the more extra dimensions there are, the smaller they can be.

if gravity is 'equal (to) the other forces' then protons would stick together. that is the whole point of the theory.

 

[humanino]

How big would extra dimensions have to be? For gravity to equal the other forces at a hundred-thousandth of a trillionth of an inch (the electroweak scale), one extra dimension would have to be as big as the distance between the Earth and the sun. Two extra dimensions need extend only about a millimeter, however, and the more extra dimensions there are, the smaller they can be.

Here we go on, hiding what a theoretician wants away from what an experimentalist can see : you may talk about string gravitational theories in another subforum. You are welcome to talk here about any strong and electroweak phenomenological model, be it stringy.

 

[granpa]

http://www.lbl.gov/Science-Articles/Archive/multi-d-universe.html

'Although the theory of gravity in extra dimensions is not string theory, which characterizes fundamental particles as bits of "string" vibrating in numerous, incredibly compact extra dimensions, Arkani-Hamed and his colleagues have shown that their theory is in fact compatible with string theory.'

 

[humanino]

Granpa, I think you are missing something here. Nuclear forces, between say protons and neutrons, can in principle be calculated from QCD, the fundamental interaction of quarks and gluons, out of which protons and neutrons are made. This by itself is a daunting task, well underway (for decades ), and completely suited to discussions here. String theory has completely different goals : to recover QCD and the electroweak part of the standard model from a more fundamental theory which includes gravity. That's all very nice, but the folks hanging around here are less versed, at least not professionaly, into string theory, and there is another subforum where you will find professional string theorists. So we can discuss string theory by itself if you really want, but you will loose your time here compared to the attention you would receive there.

Now, where to post your discussion also depends on your exact question. If what you want to discuss is how to recover the details of the standard model itself in string theory, if you have a specific string theory model out of which you want to understand phenomenology, here is good. If you want to discuss broad features of string theory classes of models, the folks in BtSM will be more knowledgeable.

 

[granpa]

my question was why can't the rate at which the nuclear force falls off simply be determined experimentally?

as far as I know this isn't part of string theory. but I could be wrong.

 

[malawi_glenn]

Who say's it can't be experimentally determined?

 

[humanino]

my question was why can't the rate at which the nuclear force falls off simply be determined experimentally?

It is determined experimentally, in various manners, mostly consistent with each other (except maybe for slight details we should not bother with right now). One aspect which complicates their interactions are the many-body forces. That's one way to approach the complications : not only do nucleons interact with one another directly, but their interaction depends on the background created by the other nucleons. This appears as 3, 4... body forces. On top of that, keep in mind that nucleon degrees of freedom include spin and isospin, that is to say they can rotate right and left, and they can rotate from proton to neutron... all that makes it so, what theoreticians do, they build a model and confront it with whatever there is available : spectra and decay mode (structural information) as well as scattering strengths (dynamical information).