Arcadian Functor

occasional meanderings in physics' brave new world

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Marni D. Sheppeard

Saturday, December 09, 2006

Review Reviewed

I'm not the first, but it looks like fun: the String theorist Polchinski has a review in American Scientist about the two books The Trouble with Physics and Not Even Wrong. I agree with much of his critique, so I will focus on reviewing the String aspects of the review.

The Standard Model is a quantum field theory...

OK, we have a problem right here at the start. The Standard Model is just that: a model. But we'll let this go, since it's just semantics and such language is common usage.

...in which particles behave as mathematical points...

OK, this one is a bigger problem. What does he mean by point? How are Strings background independent if particles have no meaning independent of classical points? Somehow I don't think Polchinski is thinking of functors between toposes when he uses the word point.

Smolin presents the rise and fall of string theory as a morality play... But this story, however grippingly told, is more a work of drama than of history.

Yes, this is quite true, but it isn't really surprising for a String theorist to think so. And why do they all keep going on about this vacuum energy idea?

The review then moves on to background independence. No wonder these guys can't stop arguing about this. Both sides think their ideas are more background independent than the other. So long as spin foams ignores things like AdS/CFT and T-duality they cannot possibly be talking about gravity, and on the other hand, as mentioned above, particles may be localised but a point is not just some piece of classical moduli. If one is willing to dive head first into Derived Categories it is difficult to understand why this is not understood. Sigh.

New physical theories are often discovered using a mathematical language that is not the most suitable for them.

Hang on a minute! What theory? I don't see any theory. Some nice maths, sure. But when you talk about T-duality there is never any discussion of Machian principles or experimental evidence for them. If I've missed such papers, please direct me to them! Ahh, wait a minute. They call it the Holographic Principle. Nice idea, but we don't actually get any physics from the way it is formulated. Again, if I'm wrong about this, please tell me!

Extending this principle to spaces with the edges free will require a major new insight.

Er, like a new Machian principle maybe? Would it be a problem if we threw out the Stringy particle zoo?

It is possible that the solution to this problem already exists among the alternative approaches that Smolin favors.

Er, well, no. That's not to say that it does not exist. Later on, the review sinks back into a discussion on Dark Energy.

9 Comments:

Blogger L. Riofrio said...

Your review makes far more sense than P's. At the risk of ticking more people off, there is way too much emphasis on background independence. Then there is the definition of a theory. If someone says that it will rain tomorrow, that's a theory. On what basis do others tell her that she has no theory? Your comments are the most interesting on blogger!

December 09, 2006 1:22 PM  
Blogger L. Riofrio said...

I do agree with your "What Theory?" One trouble with the mainstream string enterprise is that it has not led to a testable theory. (We can test if it rains tomorrow.) Your posts have given me new faith in M-theory and other fascinating maths.

December 09, 2006 1:29 PM  
Blogger Kea said...

Hi Louise

Thanks for the kind comments. I am enjoying the volcano travel stories. And life on Mars is something exciting to think about!

December 09, 2006 1:43 PM  
Blogger CarlBrannen said...

Looking around Nigel Cook's website, I discovered the inimitable Ivor Catt:

Ivor is another digital design engineer (like myself) who doesn't believe in background independence (or relativity). His interesting comment on the vacuum is that it has a characteristic impedance.

I can see the word verification again? Why not before?

December 09, 2006 3:20 PM  
Blogger Kea said...

Hi Carl

Unfortunately I now need word verification to stop spammers. I had a look at Catt's page: even though he certainly has an interesting story I wasn't at all impressed when he started criticising neutrinos, quarks and pretty well anything in Modern Physics. The guy might be right about a lot of things, and he is funny (!), but he needs to acknowledge his ignorance of a lot of physics, and this he utterly fails to do.

December 09, 2006 3:36 PM  
Blogger Kea said...

By the way, I do believe in so-called Background Independence. In fact, I take it far, far more seriously than Stringers and Loopies. So what you think of as 'non BI' physics, which I agree is good physics, I think of as 'measurement geometry'. But these geometry templates live in a richer, more abstract world. Lawvere would have called them models in the sense of logic: models of theories about observation. I'm not saying we need all this to start calculating things...after all, you guys have already proved that wrong. But personally, I will not be satisfied until there is a fully unified picture within which we can calculate truly complicated new things! And what about those deltas, Carl?

December 09, 2006 3:44 PM  
Blogger Kea said...

Ohh. Carl, I think Blogger is having problems with its Comments. Hopefully, they'll fix it soon.

December 09, 2006 3:55 PM  
Blogger L. Riofrio said...

We both believe in background independence, but it is silly when guys argue over who is more background-independent.

December 09, 2006 5:33 PM  
Anonymous CarlB said...

Yes, it's not who's got the most background independence, it's how they use it.

December 11, 2006 1:24 PM  

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