Recent content by negru

Feynman diagrams are just a way to draw the Taylor series of e^S, where S is the action (lagrangian) of the system. The action has parts that represent propagators and interactions. Expanding e^S gives a whole mess of combinations of such ingredients. Feynman diagrams are just a way of...

That's a pretty strong statement. It is implied by standard QFT. Gravity isn't the only non-renormalizable theory with a low energy perturbation expansion which is consistent. The low energy side has to be described by an effective field theory, regardless of the UV completion. This discussion...

What do you mean by "twistor theory"? Like, what are some relevant papers? I'm not sure about the first people you mention, but twistors in the way Witten used them aren't a theory, they are a now commonly used tool, like spinors or vectors. In that sense, anyone working on scattering...

It depends on the topic and the type of research you want to do, and I'm not sure about GR research specifically (not sure if there's anything going on there besides numerical stuff, if you mean just classical GR), but I'd say that the equivalent of a related course is more than enough to get...

But this can be an issue with pretty much every single topic in physics. For example just in Classical Mechanics, with dynamical systems and whatnot, there's enough theory to keep anyone occupied for many many years. If you put together all the random research topics, problems or concepts in...

You can get Srednicki's book for free, and try to find the solutions manual somewhere

20 pages in and it's all useless definitions and garbage, as expected from what is apparently a philosophy department?

Basically don't tell EE's what EE's do or what they're good for. Tell them what you did and what you're good for, and let them decide if it's good enough. Also drop some of the unnecessary flattery like " I had the privilege of presenting the research", "I was fortunate enough to join the...

I would just cut all of the personal opinions on stuff, like why you think EE's are important, that you're doing this for financial stability, that you regard yourself as an ideal candidate, that UCI has a diverse student body. Also splitting the essay in parts is not a good idea. You don't...

Start with a massless spin 2 field, which couples in some consistent way to the stress energy tensor, and couples to itself. I thought it is accepted in the literature that this leads to full GR? Some alternative assumptions also work http://arxiv.org/abs/0811.3207

On the other hand, starting from just gravitons, one is able to derive GR, no? So one can assume higher order terms can also be described by gravitons.

Here's a dumb question: is there any evidence for GR beyond the linear terms?

It's irrelevant whether the graviton is fundamental or an effective d.o.f. It still has to be there, just like hadrons are effective d.o.f in QCD, but they are very much there, with the expected properties. Technically gravitons are effective d.o.f. in string theory too.

It's not immediately obvious to me that a new theory of QM will solve these problems. Identical problems appear for other theories as well, like chiral perturbation theory, not just GR. They are all solved by realizing the theory is not complete and adding new degrees of freedom. If a new...

People should be extremely conservative with regard to old theories until strong evidence shows up to prove them wrong. Otherwise what, every time some guy comes with a new theory we start jumping up and down?