String a failure: Nobel-laureate in today's NY Times

[Martin]

... how many theories out there refer to there being more than one dimension of existence where things exist other than 3 and or 4 dimensionally,...

 

Loop Quantum Gravity is a theory which has been constructed to work in any number of dimensions

It is still being worked on, but so far no obstacle has appeared that would prevent it from working in a world with say SIX or maybe SIXTEEN dimensions. I dont recommend LQG merely on that count, other non-string quantum theories of spacetime also have this freedom about dimension, like Ambjorn dynamical triangulation model for instance.

 

however up til now there is no evidence of any more dimensions than 3+1!

 

So I think it is hazardous to be developing a theory like string which is limited to some definite number of dimensions, like ten. What if it turns out that there are only 7? Or 9? Or maybe just the 4 we know about?

 

in these cases several non-string quantum gravity approaches would continue just fine, but string wouldn't work.

 

A string model has this weakness that it is picky about dimension, wont work unless dimension is just right.

One possible scenario might be someday an experiment gives strong indications that there are not the extra dimensions that string requires, but just 3+1 or some other number, and that this then would help to pop the string bubble and get the research brains and money re-allocated.

 

Brian Greene has said that among other possibilities it would be great if string were proved to be wrong so that physics could move on (but likewise great if it were confirmed too!) and this dimensions thing might be just the ticket to prove it wrong and get clear of it.

 

so far, no indication of extra dimensions after 20 years of string

 

I rather guess that spacetime has dimension 3+1 and that when we finally get a working quantum theory of spacetime IT WILL EXPLAIN why there are just 3+1. that is just my personal point of view, but that is what I think most likely

[ExplorerLeia]

Just wanted to say, "Thanks Martin."

 

I have always wondered about these types of ideas and your input has helped me a great deal.

 

Leia

[jdurg]

Hmmm. Interesting. To me, the whole string-theory/anti-string-theory debate has seemed pretty similar to the Phlogiston/Anti-Phlogiston debates that occured in chemistry a long time ago. The Phlogiston theory was developed without any real proof of existance and was constantly changed to meet whatever experimental observations were found. It wasn't until absolute conclusive proof that it was wrong was discovered that people began to abandon it. Still, some scientists held strongly to their beliefs and never accepted any other theories. I think a similar thing may be happening here. I've always thought that the quantum level of science was always very intersting, but always made my head hurt. lol. I am very fond of radioactivity and what causes it, and would love to see research done so that someday we could have a way to safely dispose of our nuclear waste that is constantly piling up.

[Martin]

A lively debate in the Daily Free Press

 

http://www.dailyfreepress.com/news/2005/01/25/Science/The-Thin.Line.Of.Theory-840583.shtml

 

it has interesting pro and con quotes from Harvard and BU physicists, including passionate plugs string theory from string theorists and all that.

 

the article goes on for 5 pages but the paper wants you to register

to read beyond the first page---registering is free and simple to do, dont give any information except yr email address---but I wish access were completely open. I guess you could give a wrong email address and it would still let you read, because it does not check.

 

the people at BU regard string as a dead-end and a passing fad so they dont hire string people for the faculty, but instead emphasize areas of research closer to experiment and reality, and they say this makes their department stronger in nationwide standings.

 

suggest reading whole article. A string theorist at Harvard, Cumrun Vafa, got quite excited when he was interviewed by the reporter. and so did others. makes for good reading. a bit over the top in places.