Recent content by Micha

To get an idea what string theorists are up to nowadays have a look here: http://arxiv.org/abs/1104.5502" Pretty impressive stuff.

You mean all calculations in QFT. In string theory pertubation theory for gravity works just fine.

Ok, so that is a pretty strong claim. Where is the reason?

Ok, great, so pertubation theory only works on tree level. Feynman should give back his Nobel Price and Feynman graphs never existed. You should have made a good argument specifically for gravity. But unfortunately you didn't and wrote about QFT in general.

Physics is not a contest in who is more polite or more politically correct but about what is true. So this argument is a non-starter.

I know a little bit of QFT too. Of course if you study it in the regime where the coupling is of order one like the low energy regime of QCD then pertubation theory breaks down pretty much by definition. It works well in QED where the low energy coupling is week. As we all know gravity is...

The problem with "trust the experts in a certain field" is that it won't work if the whole field is flawed. That it is what Lubos claims and I would like to encourage you to seriously consider the possibility. I agree Lubos is not an easy character. But I claim you would get pretty much the...

Right, background independence is the new religion. 300 years of successful pertubation theory are thrown out of the window. That's ok but I think it is not only a problem with you. :-) I am following the blog of Lubos Motl for quite a while and I am convinced he is a top shot...

Great, so these guys do quantum gravity but they don't calculate the properties of gravitons. Regarding background independence have these guys ever heard of pertubation theory? Unitary is a basic requirement of any theory which claims to be quantum mechanical. It just means that...

What about gravitational waves? What about the even more fundamental requirement of unitarity?

How do the CDT people ensure that their path integral is unitary and does not contain superluminal effects? If these conditions are not met there is no hope that the theory is confirmed by experiment.

Here is a clear and I think deep article from Lubos Motl about the path integral: http://motls.blogspot.com/2010/10/dont-mess-with-path-integral.html Looking forward to Marcus reaction.

If you are serious to become a good physicist, I think you should read this: http://www.phys.uu.nl/~thooft/theorist.html

Yes I read it. When I read your discussion of the error function, I just thought, that I remind people of the Taylor expansion. It is a trivial point of course.

Hi MTd2, as any smooth function, the Lorentz violating effects, in this case the deviation of the speed of high energy photons from the known speed of light as a function of energy, can be developed into a Taylor expansion. So whatever the exact form of the function is, it is zero in the low...