Recent content by LBloom

It's not, U(N) and SU(N) are never isomorphic. Maybe in the large N limit all the relevant physics is encoded in the SU(N) and any extra group factors from U(N) correspond to center of mass motion of the branes, but that concerns physics not group theory.

1) QFT does not equal special relativity + Quantum mechanics. There are nonrelativistic field theories and they are used in condensed matter physics. And there can be nonlocal field theories, a field theory is just quantum mechanics with infinite degrees of freedom (a field is defined throughout...

Diracpool: Lee Smolin is not exactly an objective observer, he criticizes string theory and in the same breath promotes Loop Quantum Gravity, a theory which by all means should be studied, but is also currently untestable simply because the effects of QG are so small. Also about going from...

Oh also about technical refutations of string theory, there aren't any. And whenever people do caluclations and compare them to the gauge theory results through holographic dualities it always works. That and in string theory you can derive that the area of black holes scales with the area as...

As Mark Twain once said: "The news of my death have been greatly exaggerated". The same goes for the way string theory is often treated in this forum. Yes the unification program in string theory has slowed down. That's not because no one believes its true, if SUSY exists, which is by no...

On the topic of problems in LQG, does anybody have good literature or explanation of the problem of getting a flat universe and/or the Einstein equations in the semiclassical limit?

I assume you're referring to blackwagonninja because I didn't have any questions about holography and was trying to explain the distinction between AdS/CFT and holography. That they are not equivalent terms. In fact I never mentioned the contents of the paper because I have not read it yet...

AdS/CFT dualities obey the holographic principle, but not vice versa. That is the holographic principle is an older and broader concept then AdS/CFT. AdS/CFT refers specifically to just one kind of duality where the holographic principle comes into play. The AdS/CFT duality is not a...

No actually mitchellporter is right. The AdS/CFT correspondence is not just that the symmetry group of AdS space and 4D conformal theories are the same. The fact they are the same points towards a duality, but this coincidence does not a duality make. In order to proof there is actually a...

ktb, Yes they were all NSF sponsored as all REUs are. I would also consider applying to SULI if its not too late or look at the Caltech SURF program. I've been accepted to the minnesota, sbu, indiana reu programs and the fermilab suli program. There were a lot I never heard back from...

As a white male from a large research university who got accepted to a few REUs last year, I would say yes, its worth it to apply. REUs do try and help people from small research universities, but its not always the case. In one REU I was a part of we had three people from the home...

Like a lot of dualities and ideas in physics there is no proof for AdS/CFT and I don't see there being one for awhile. Its hard enough to make QFT rigorous by itself! Also AdS/CFT is a little broad. There are a lot of dualities that go under AdS/CFT, the most famous one being what Juan...

FV89, There are two different things at play here. Whats on the superstring theory website is about possible corrections to Einsteins theory of gravity that are predicted by String Theory. String Theory should reproduce GR in the low energy limit (theres the natural appearance of the...

In supergravity the affine connection is not required to be symmetric and the torsion part is allowed. I believe this was first shown to be possible by Cartan but I could be wrong. The problem with this paper is that it looks like everything is done classically so I don't think it really has...

The DAMTP program does have courses for theoretical physics. You can look up the course catalog online but it includes topics like QFT & Strings, Continuum mechanics, and Cosmology. You can take 17-19 credits for examination, so if you try to take every course from the QFT & Strings category...