Choose Your Path: Strings or Loops?

[Casco]

This goes for the people of loop quantum gravity and string theory. Think that you want to convince a very smart student of going into your field (strings or loops). How would you convince him ??

But, by doing it on a 5 lines paragraph talking about your theory and a 5 lines paragraph talking about the other one.

It is assumed that the student it is interested equally for both.

 

[humanino]

This is a poor beginning for a researcher. You should be able to make up your own mind, at the time you need to actually make the choice, based on your own preferences. My take is : go where I don't work.

 

[Casco]

This is a poor beginning for a researcher. You should be able to make up your own mind, at the time you need to actually make the choice, based on your own preferences. My take is : go where I don't work.

I think that I should have mentioned that the purpose of this thread is to make a discussion about this two theories, in order undergraduate students like me, so we can have a deeper vision about them.

 

[humanino]

Have you completed your study of general relativity and quantum field theory ?

 

[Casco]

Have you completed your study of general relativity and quantum field theory ?

General relativity yes, about QFT let's say nothing.

 

[humanino]

Well, I will not be able to continue right now, so I will quit doing the devil's advocate. Before leaving I will add a couple of more constructive points.

The simplest way to decide for you is : once you have learned quantum field theory and general relativity, go for the approach which you feel closer to. String theory clearly grows out of quantum gauge fields. Loop quantum gravity is more on the side of general relativists. But : there are other approaches as well ! So do not forget them either.

The two first are rather old by now, but in case you have not read yet :
A dialog on quantum gravity
Loop quantum gravity: an outside view
A critical look at strings

Good luck in your investigations.

 

[marcus]

I think that I should have mentioned that the purpose of this thread is to make a discussion about this two theories, in order undergraduate students like me, so we can have a deeper vision about them.

To get a deeper vision you should not set up a debate. The adversarial "fight" framework will not lead to a deeper understanding.

Personally I find everything Humanino told you to be just right. He and I are interested in different areas of research (I follow mainly LQG research, and he mainly string I think) but I strongly agree with what he said to you.

Maybe you can rephrase the question in a more constructive way. Try this: imagine you have already decided to go into NEITHER ONE but have chosen an entirely different specialty, say COSMOLOGY. Then ask the same people to tell you what they think you should know about stringloopery. For breadth, a young cosmologist should probably know something about both the string and the loop research programs.

You asked for "5 line paragraphs". I think a young cosmologist should know at least that much about both loop and string research---probably more.

Indeed there was just last month an elite weeklong workshop on loop AND string as they apply to current questions in cosmology, with top experts in all three fields. It was on the Greek island of Naxos. I will get a link.

These days the theme is no so much "this versus that" as getting together and sharing ideas about the real problems (like early universe and dark energy or if you prefer the cosmological constant.)

Also the beginning of the LHC era has changed things drastically for particle theorists. It is a new ballgame. People who 5 years ago would have been doing nothing but string are shifting into areas that have more to do with what the LHC can explore. It does not look as if the LHC will say much about string but it will cause a big ferment in ordinary non-string particle theory. People are trying to think up alternatives to the lowenergy supersymmetry and the standardmodel Higgs field which everybody expected but so far have not shown up.

I'll get that Naxos workshop link. Major people like Kelly Stelle, Abhay Asktekar, Robert Brandenberger, Costas Bachas, Carlo Rovelli, Joe Silk.
https://www.physicsforums.com/showthread.php?p=3510863#post3510863
http://www.physics.ntua.gr/cosmo11/Naxos2011/sci_prog.html

Lately the stringsters are not staying in their own clubhouse, they are getting out and mixing with the loopsters, it's the order of the day And a lot of people are crossing research lines (I think because of what LHC is finding/not finding----or will be able to test over the next decade.)

 

[tom.stoer]

The simplest way to decide for you is : once you have learned quantum field theory and general relativity, go for the approach which you feel closer to. String theory clearly grows out of quantum gauge fields. Loop quantum gravity is more on the side of general relativists

...

The two first are rather old by now, but in case you have not read yet :
A dialog on quantum gravity
Loop quantum gravity: an outside view
A critical look at strings

I agree with humanino's recommendations.

Another short remark: strings are an approach towards unification of all forces including gravity, whereas loops are an approach to quantize gravity w/o taking other forces into account; in a second step one can add other forces on top (including supersymmetry / supergravity), but there is no attempt for unification, just for "compatibility".

 

[mitchell porter]

Someone interested in the difference between loops and string should study the difference. String phenomenology is carried out at a level of approximation somewhat removed from the distinctive problems of quantum gravity. The pluralism of LQG is such that there are many opportunities for conceptual comparison between LQG and the "QG" part of string theory.