Does String Theory Predict more than Four Forces?

Question

String theory literature tells us that ST predicts the four forces: weak, strong, EM, and gravity. What it fails to tell us is if that's all the forces it predicts. Might there be a fifth force that ST predicts, but was thrown out because there is no observable evidence in 4D space that a fifth force exits? Might that fifth force, if there is one, account for the so-called dark energy in the universe?

Greene, Witten, Kaku, and others on the string train all mention the "four forces" unified by ST. But none mentions if only those four forces are predicted by ST. Might it be possible the fifth and higher forces predicted by ST are simply not mentioned because there is no evidence in the standard model of a fifth or higher forces? Is there someone out there in answer land who has actually seen and understands the ST results?

Answer 1

I am not a string theory expert, but I do know how physicists think (I am one - at least I'm in grad school to become one). String Theory is an appealing theory because it provides a way to unite all 4 forces of nature (well, 3 - EM and weak have been combined to form electroweak), in particular, it reconciles gravity to the other 3 forces. So when you ask could it predict a 5th force, what you are really asking is whether there is a unique interaction in nature that is significantly different enough to be counted as a "5th force" (but still be a part of the unified forces). I have not heard of such a prediction. If it exists, it would have very tight constraints on it due to what we've already observed in Nature, so it would have to have an interaction length on a very small scale (small scale = high energy in physics since you need high energy to probe on a small scale). So, a prediction of a 5th interaction would be used to 'weed out' unacceptable theories based on what we know, but if the 5th interaction was predicted to exist at a certain energy that we can measure at the next generation particle colliders (like the Large Hadron Collider - LHC being built as we speak), it would be taken VERY seriously. Alternatively, we might find such a force without predicting it, but that seems very unlikely to me.

Dark Energy, as far as i know, is still not explainable within string theory because we really don't know what it is, but there's some ideas. Whatever it is, it hasn't shown up yet in our particle accelerators. It seems to be something more than a 5th force since it affects all of the universe (like spacetime itself if I understand right). In either case, I have not heard of string thoery explaining it. I've heard of "quintessense", modifications to gravity, and other possibilities too hard to explain here. But until an accelerator detects something that has the observed properties of dark energy or dark matter, these two things are going to remain a mystery.

String Theory has a lot of possible predictions, but very few observable ones. That's why it wasn't considered a legitimate theory until recently.

Answer 2

Imagine flatlanders, trying to figure out all the rules of three dimensional space (geometry, trigonometry, etc). It seems that they are not even equipped to truly grasp all that they need to grasp. They might observe a single point, appearing out of nowhere, then growing in diameter until it finally begins to collapse back in on itself and finally disappears completely in a single point. They could have a dozen theories to explain this strange observation, all of which might or might not include the possibility that a third dimension exists, and that a 3D object just intersected their 2D landscape for a brief time.

Now, imagine us, stuck in our little space-time, trying to grasp all that is, or at least, all that we can see. No doubt we are totally unaware of *most* of "all that is," and we are really under-resourced to explain it all.

That said, we can observe some strange things that don't really make sense to us. Maybe the answers will come from a perspective that is based on assumptions that we have never considered. The question is, how do we bring ourselves to consider these things from such unique and different perspectives?

I think the constant observation, testing, theories etc is a good way for us to try and expand our experience. I am very excited at the prospect of actually testing quantum physics in ways that we have not yet been able to do... the future is indeed bright (if we make it that far!)

Answer 3

No! It better not.

They whole point of any theory is to describe reality a.k.a. the world around us. In the world we know of four forces and string theory is an attempt to describe and unite those forces. If it predicted a fifth force then it would not describe the world as we know it.

Please note that string theory is just that a theory. It has yielded no revolutionary ideas that can be tested in a lab. The prediction of a 5th force would be an idea that could be tested experimentally.

Answer 4

what a great question. string theory of course is trying to unify all of the currently 4 observable, defineable forces we now have. if unification is possible then all forces will become variants of a single set of 'extradimensional relationships'.

i love the dark matter part too. especially if it's the dark matter holding this expanding universe from flying forever apart. my guess of course is that dark matter behaves alot like light matter but that some aspect of its 'dimensionality' is 'out of phase' with ours. the extra dimensionality of string theory opens a lot of potential doors.

so to finish, i don't think string theory actually calls for more forces. no. if all things are connected, it mererly opens up the number of ways in which 'the things' are connected. myself i think its the trying to wrap your head around the other dimensions in any meaningful or thorough way that will eventually become the most of this story.

Answer 5

String theory is really like a blank slate. It could handle a fifth fictitous force on that account.

Richard Feynmann when asked about string theory said: It's nonsense.

Answer 6

Too deep for me, but I like the question! Rock on eyeonthescreen!

Answer 7

Time seems to be left out of those theories

Answer 8

yahoo search kaku- michio kaku -he is brillant and has your answers to string theory

Answer 9

the string theory is aflop...some have concluded over 40 dimensions, while others derive completely different solutions. some of these people will fake it for more grant money...happens alot !