# B Strings as Hoola Hoops

1. Mar 29, 2016

### Dook

Is this correct? Strings are one dimensional objects that form circles (hoola hoops) that flip in certain directions as they move through space. The strings can collide with other hoola hoops and break, then reform into other hoola hoops with different properties.

2. Apr 4, 2016

### phinds

You are leaving out the fact that stings can be closed (which you describe) OR open. I'm not talking about a broken hoop that reforms, I mean just a string.

3. Apr 4, 2016

### ProfuselyQuarky

So what would be a good analogy?

4. Apr 4, 2016

### phinds

Why do you need an analogy? There are open strings and closed strings.

5. Apr 5, 2016

### Demystifier

Hula hoop is not a good analogy because hula hoop is rigid while string is elastic. A much better analogy is a rubber band.

Last edited: Apr 5, 2016
6. Apr 13, 2016

### newjerseyrunner

And if I remember correctly, the only thing that would be composed of closed strings is gravity. Everything else must be open.

7. Apr 13, 2016

### MacRudi

We have 3 closed strings
graviton with spin 2
Axion and Delaton with spin 0
all 3 massless
calculated out of all stringtheories and several M theory T duality cases the Axion is massless (Witten), different to quantummechanics predictions that Axion should have mass for dark matter
These are the earliest natural predictions out of string theory

8. Apr 13, 2016

### JorisL

If you are interested in the states (particles) that show up in string theory, I liked the treatment in Theissen and Lust's book which explicitly looks at the "full" spectrum of states.
Are you sure those are the same axions?
I know that there are several things we call an axion in string theory. A while back I encountered axions in a particular parametrisation of the metric on an internal space. They aren't the same as the Peccei-Quinn axions. (I think you meant those?)
It had something to do with the way the scalars show up in the action, if it show up in a certain form people call them axions. (details are foggy)

9. Apr 13, 2016

### MacRudi

There are 2 Modells out of the 80s. But I'm not sure if this is today meant, what you mean.
I mean the Pecci Quinn Axion
you mean maybe the building up out of branes?
Or do you mean the Axino?

Maybe I have to look in Kusters textbook. If you have concret informations I would be glad to see it.

Last edited: Apr 13, 2016
10. Apr 13, 2016

### JorisL

The problem is that often we use the same name for quite different things.
I was wondering if the axion you spoke of was the PQ axion or one of those that just get lumped together because they are the same if you look at them from a distance (i.e. without looking closely).
An example could be states with the same index structure as a photon, you still have to check that it actually _is_ a photon.
With axions this sometimes doesn't happen.

I'll see if I can dig something up although it will likely be for next week as I'm busy at the moment.