Wednesday, March 19, 2008

Strings @ BYU

Well the title is a bit deceptive but for guys like me March 25th is going to be an exciting day. The reason being: Brian Greene is giving the University forum address next week. That's right, on the 25th of March, 'the Elegant Universe'-man himself is coming to talk about his latest book, "The Fabric of the Cosmos." Needless to say the Harold B. Lee Library's copy of that book is currently checked out by me! I plan on being there extra early to get one of those comfy seats on the Marriott Center floor and hope to be armed with a multitude of questions to ask during the Q&A session. That's part of the reason why I am writing this blog now instead of waiting to just give a report: I need some questions to ask! So whatever curiosities you all may have please send them my way and I will be happy to ask them for you. Personally, I am really curious about the future of string theory in terms of soon-to-be experiments, previous experiments (like the length scale tests of gravity @ Washington) and astronomical/cosmological observations. I may really like string theory but I get so caught up in that I would like to take a step back and play the pessimist. You know just to get a better look at the 'big picture.' In addition, strings are such a broad topic that it's difficult to have your hands in more than one or two areas of the research. I would like to get better introduced to some of the other research that's being done. So email me or comment your questions and I'll see how many questions I can ask before I am forcefully removed from the Q&A session!


  1. Brian Greene coming to BYU? That's great, too bad I can't be there.

    Look, people who criticize string theory usually don't know what they are talking about.

    Are the legitimate reasons to criticize it? Of course, but, with out going into details which I will in the future, the reality is string theory is a very important theory and needs to be studied.

    Again, it may not be true but believe me "WE ARE SOOO MUCH BETTER OFF AS A PHYSICS (and math) COMMUNITY FOR TAKING TIME TO STUDY IT." This will continue to be true for some time to come.

    With that said, I think the most legitimate critique of string theory is: it is taking much time away from phenomenology.

    Don't give me the "It's not testible" line. There are several ideas *that came from string theory* which are some of our most exciting things we are about ready to test. Ie supersymmetry for starters.

    Thank string theory for testable ideas like this. (Not to mention the volumes of new math useful all over.)

    Again, the legit critique is it takes away from phenomenology. (The testable ideas that come from it) Too many smart physicists are doing great work in string theory but are only worrying about the wrong energy scale. (Come on guys, apply the cool ideas to the TeV scale!)

  2. To sum up what I just said:

    Even if string theory is false it is a massive "interesting idea" creating machine.

    Name any other modern theory where more very interesting ideas, again testable ones like supersymmetry, are being generated. (I guess this is subjective, so will say new ideas with 1000s of citations!) Ideas like Ads/CFT, branes, supersymmetry, topological artifacts in nature, etc... are well sighted, very interesting ideas with testable predictions.

    All of them and many more came from, and will continue to come from string theory.

    I just hope we don't generate so many interesting ideas that we loose track f the fact that people have to apply them to the real world. Ie. phenomenology.

    Perfect example: D-branes are an incredibly useful idea: could explain inflation, why gravity is weak, etc..

    However, instead of focusing on these above "practicle" ideas ***some spend all day studying D1/D5 black holes!!!*** :) :) :)

    Ie, great minds distracted from phenomenology. (Using string theory for real world ideas.)

  3. haha, Joe you're such a fireball! I'd never want to get into a debate with you. It's apparent that I am not as well-read as you are in these areas so I don't even know what peoples complaints are when it comes to string theory. One I haveheard recently, thanks to a colloquium speaker, was that strings yields a cosmological constant different than that of observation. I am really curious what other criticisms people have and what solutions there are available. Keep it coming Joe, thanks!

    P.S. I am still doing heterotic model building while dust collects on my D1/D5 poster in the hall!

  4. Jared, here is another perfect example! Specific string models often incorrectly predict the cosmological constant.

    However, M-Theory says there are somewhere around 10^500 consistent string models. Each one has a different value of the cosmological constant ranging from -1 to 1.

    These models together form the string landscape. You can think of the string landscape as a "landscape" of potential wells were each one has a different value of the cosmological constant. If our universe is in the right well string theory would predict the correct cosmological constant.

    This has profound implications. Raphael Bousso's lectures on the subject here are fun to watch. See Tasi 2007 web page and go to videos.

    Now, this has generated huge interesting ideas for cosmology.

    ***Even if string theory isn't correct*** we are pretty sure that inflation is caused by our universe being in the ground state of some potential well, then we a "boost" up the well for a while while the universe inflates. When we come back down inflation is over and the ground state determines the cosmological constant.

    Now, from string theory we get the great idea that the "potential well" that quantum fields may have different ground states. This ideas remarkably has great implications for supersymmetry breaking and could very easily explian the cosmological constant problem.

    Even if you didn't follow the take home message is:

    ***Even if string theory is wrong, the string landscape, a possible solution for the CC problem, has led to several interesting ideas that may help us understand inflation, supersymmetry breaking and the CC problem in very interesting and testable ways!***

    Again, citations from "string landscape" ideas are through the roof.

  5. i like the comic strip you got of the string theory.
    ok what would that imply?
    i don't know.

    also can i read that copy when you're done? if his book is like how he talks, i bet it'd be crazy awesome.
    ps i loved the forum today.


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