# Tag Archives: String Theory

## Compactification in String Theory Part I: Motivation

A new attempt to reinvigorate the blog!

Yes, I am aware that I already have two physics related threads that have started and ended at “Part I” (false vacua and string theory). However, I’m really motivated by the introductory explanations. I promise to come back and finish the other ones real soon. But for a while, I’d like to talk about compactification.

A word about the word…I’ve had at least two scientist friends laugh when I’ve said “compactification”. Also, the text editor I’m typing this in thinks its a misspelling. Apparently in all other science fields, the correct word for taking big things and making them small is “compaction”.

Well, we string theorists are just a little bit cooler then you “real scientists.”  We’re not taking some obsidian and making it smaller (like my roommate, the geologist, and one of the laughers), we’re making goddamned extra dimensions smaller. You read right, the extra dimensions.

For casual, non-specialist readers (if there are any left) the first few posts will be an introduction–an attempt to explain WHY we need to “make the dimensions smaller,” what that means, and why its so hard. I hope to follow up much later with more technical issues and a few comments of my own very small research in this subject. At the very least, you will be able to read pretentious, unfunny Woody Allen short stories and chuckle with smugness.

Ok, so let’s get on with it.

## What is String Theory Good For (Part I)?

This is, I guess, my foray into the bloggy string wars (or the stringy blog wars?). But not really. I just want to give you some of my brief perspectives on why string theory is kind of a big deal. This will possibly precipitate screaming and gnashing of teeth in the comments section, but whatever. It is not my intention to get into some sort of flamewar (or whatever the kids are calling it nowadays) so I probably won’t respond to any comments.

A short list of what you might think string theory is good for.

1. Nothing–unlike a lot of my colleagues, I think this is a perfectly reasonable perspective. In fact, if you had this perspective about all of particle physics, I think it also would be perfectly reasonable. In short, what we do benefits absolutely nobody. We should all probably be using our brains to search for a cancer cure.

However, I find to stomach arguments that other completely useless things–like calculating the QCD beta function to n loops, or calculating the homotopy groups of spheres is somehow more worthy. Usefulness is not why most people engage in many areas of math and physics.

## Podcast Self Promotion!

Sorry for the long time since last post. Today I have a shortish lunch talk to all types of physics graduate students. The talk was titled “Physics at Strong Coupling: Why String Theory and Supersymmetry are Ridiculously Cool, Part I,” with future parts to follow in the coming years. The talk went ok, I hope I convinced some graduate students that string theorists are not completely crazy.

But maybe now I can convince you! A friend helped me make the talk a podcast, with audio track and all. You can subscribe to it (and future, podcasts, I guess) here. Hitting “subscribe” on that page imports it into your i-tunes. Let me know if you enjoyed it! I guess, also let me know if you did not enjoy it…

## Physics Envy on a Cold Day

I read a post by a biologist philosopher about how supposedly physicists are undertaking “stamp collecting.” And I’m fairly annoyed that they missed the entire point. They read this article on attempted classification of string vaccua, and likens this attempt to taxonomy in biology, in their eyes lowering physics to a descriptive science. This whole flame war started with Rutherford claiming “In science there is only physics. All the rest is stamp collecting.” Let me liberally translate to clarify: “In science the only quantitatively predictive field is Physics, and everything else is descriptive.” This certainly was true in Rutherford’s time, but discovery of atomic structure elevated Chemistry to predictive, and the discovery of DNA elevated biology. Now we’re all buddy-buddy. In real science, 99% of the time you first gather data, then classify, then build models, and then you have a quantitative principle to make predictions. This went faster with physics because we deal with much more homogeneous systems. An old friend and ex-ZEUS student I know is now writing Monte Carlo simulations for Neuro Bio. That aint taxonomy. Heck, even economists have real models these days, and their particles have agency.

The big missed point is the following: String Theory isn’t predictive, or descriptive, yet. It has never made better than tenuous qualitative connection with reality, and I wouldn’t bet any money that it will improve soon. Why? Because its history is all bass-ackwards. It may have started from meson spectroscopy and QCD flux tubes in the late 60’s, but then everyone thought they smelled gravity and got the great idea to start from a unprobeable scale and grope their way back down to experimentally plausible energies. In string theory you first assume an underlying principle, then build a phenomenological model, then gather data. This isn’t to say its totally unmotivated, but it does incur a large investment risk.

The authors whole point is that stamp-collecting is a type of science, and shouldn’t be looked down on. This is half true. It is necessary for developing falsifiable theories, but should not be considered a form of science in itself. People can gather data, and arrange it in clever ways, but without predictions and basic principles, There’s very little objectivity, or application.

So biology in Rutherford’s time was like stamp collecting, but all those stamps they collected were issued from a genuine authority. Woit claims the String Vaccua Project “…is stamp-collecting done by people who don’t have any stamps, just some very speculative ideas about what stamps might look like.” He breakdown of the string vaccua project on his blog, if you want to read more. He also comments on the original biologist’s philosopher’s post.

Edit: Dr. John S. Wilkins, the author of said blog, is a postdoctoral research fellow of philosophy, not biology, as originally stated.