10th

[papernuke]

Are there 11 dimensions or 10? I read in this book and it said there were 10 not 11.

[jinydu]

A certain version of string theory, which is currently unproven, states that the universe can be described by an 11-dimensional structure.

[houserichichi]

String Theories

Type
Spacetime dimensions
Details

Bosonic
26
Only bosons, no fermions means only forces, no matter, with both open and closed strings; major flaw: a particle with imaginary mass, called the tachyon, representing an instability in the theory.

I
10
Supersymmetry between forces and matter, with both open and closed strings, no tachyon, group symmetry is SO(32)

IIA
10
Supersymmetry between forces and matter, with closed strings and open strings bound to D-branes, no tachyon, massless fermions spin both ways (nonchiral)

IIB
10
Supersymmetry between forces and matter, with closed strings and open strings bound to D-branes, no tachyon, massless fermions only spin one way (chiral)

HO
10
Supersymmetry between forces and matter, with closed strings only, no tachyon, heterotic, meaning right moving and left moving strings differ, group symmetry is SO(32)

HE
10
Supersymmetry between forces and matter, with closed strings only, no tachyon, heterotic, meaning right moving and left moving strings differ, group symmetry is E8×E8

****************(taken directly out of a wiki)

11 dimensional spacetime is M-theory; a generalization of the five string theories into one.

[papernuke]

A certain version of string theory, which is currently unproven, states that the universe can be described by an 11-dimensional structure.

Then was the book wrong? Because it said the highest was 10.

[jinydu]

Then was the book wrong? Because it said the highest was 10.

See houserichichi's post.

[bo198214]

Yeah, house can again shine with his broad physics knowledge

[papernuke]

Dude, I'm only 11 how would I know what he's talking about?

[houserichichi]

Bosonic string theory has 26 dimensions, I, IIA, IIB, HO, and HE string theories have 10. Bosonic string theory can't describe our universe because it only has bosons and not fermions (electrons and quarks are fermions and also the "stuff" that makes you and I up, and since they exist in our universe bosonic string theory can't be the "right" theory because it doesn't include them). Ed Witten showed that the other string theories are all one in the same thing that describe an 11-dimensional superstring theory derivative called M-theory.

The unfortunate thing is that there has been no evidence to support any of these string theories yet...the hope is coming from the soon-to-be-completed Large Hadron Collider which I believe goes up and running in 2007 so we'll have to wait and see.

[thigle]

hey house it seems you're one of most physics informed guy here on these forums. that's why i wanna ask you: what do you think of Tony Smith's TOE attempt ?

[houserichichi]

Oh dear, I simply copied out of a wiki, I'm no more enlightened than the rest...I think the real physicists on this site are jinydu and wendy by education. I'm just a mathie with lots of time on his hands :wink:

As for Tony Smith's page, I've been there but have never given it a thorough readthrough. I'm curious why he was blacklisted off the preprint server. I've read through his diatribes but I can't seem to find the actual reason outside of him trying to publish 'fringe' science through a personal email account rather than a university one.

At any rate I'll try and give him a read over the coming weeks with an open mind and let you know. I think August will be a busier month than the rest of my summer!!!

[papernuke]

I, IIA, IIB, HO, and HE string theories have 10.

What do those letters stand for? I, IIA, IIB, HO, and HE?

[houserichichi]

Just naming schemes. I, IIA and IIB are roman numerals for "one", "two-A" and "two-B". HO is heterotic and I believe O for "orthogonal" as the symmetry group of HO is SO(32) the 'special orthogonal group' of 32x32 matrices. HE stands for heterotic and probably the E for 'exceptional' as the symmetry group of HE is E8xE8, two copies of the exceptional group E8.

[jinydu]

I think the real physicists on this site are jinydu and wendy by education. I'm just a mathie with lots of time on his hands :wink:

Thanks, I'm honored. But my knowledge of physics is a far cry from those of real experts; I haven't even finished all the undergraduate physics courses at my university yet. Still, I do know far more than most of the public does (which alas, is very little in my opinion).

[houserichichi]

Don't worry, even the experts aren't masters of all trades in the field. Fact is you have more formal education than the rest of us, I'd imagine. I find the one perk to having the math under my belt is that I'm able to get a lot out of the preprint servers without the necessary background in physics. Outside of that, however, I'm quite limited in my ability to express concepts and ideas beyond basic descriptions. I'm in the process of finishing Shankar's Quantum Mechanics, Misner, Thorne, and Wheeler's Gravitation, and Griffiths' Elementary Particles. Cross your fingers that I'll be of more use in the near future.

What sorts of background do you have these days? What are you, third year now?