Recent content by clerk

I am sorry if this sounds too philosophical but thanks for any inputs .. String theory claims that every particle in this universe is actually a manifestation of vibrations of fundamental strings. But how do these strings came into existence in the first place ? I understand the concept of...

Hi friends, I was wondering about the following - in GR texts we always see these penrose diagrams and some line representing the horizon and all these timelike , spacelike curves and all that ... but the picture that I have of GR is just that of a smooth 4 manifold endowed with a metric . Can...

Hey thanks a lot ! That was so nice :)

@all : I also enjoyed Zee's QFT book a lot .. infact it is the one from which I got a very nice picture of what QFT is .. Sorry I keep asking for clarifications , I will be grateful if anybody explains a bit more about what "co-ordinate acceleration due to gravity " is .. As WannabeNewton...

WannabeNewton : I agree with you .. I was never able to digest that statement.. but at the same time felt that may be I am missing some deep secret of GR , feel more relaxed now.. :)

@all - thanks a lot for the stimulating discussions .. Just one more clarification - in the popular QFT text Anthony Zee makes the comment that under suitable restrictions , the effect of a gravitational field is equivalent to a co-ordinate transformation - how exactly do I see that ...

Thanks a lot , Tiny Tim ! In the 2 -sphere example , I wanted to understand the required co-ordinate transformation that would reduce the metric (1, sin^2 theta) to (1,1) ..if it is locally flat , I should be able to explicitly show that , right ? Also please will you see if my following...

Hello friends , I have some conceptual problems in understanding the difference between Minkowski spacetime and the spacetime of general relativity. The general spacetime of GR is defined as a smooth manifold which is locally like Minkowski spacetime . What does this statement mean ? Does...

Thanks a lot.. that was really very helpful. So even though I cannot get the exact propagator , I can get a rough estimate of the renormalized mass to any degree of accuracy by increasing the order of feynman diagrams at a given energy scale in a renormalizable theory.Next I perturb around...

I am confused about the idea of mass renormalization in quantum field theory. Firstly, in case of charge renormalization there is a picture where you have a swarm of particle antiparticle pairs round the electron and hence depending on the energy of your probe , the charge gets renormalized...

Thanks a lot . Interestingly,I found a section in Zwiebach where he discusses gravitational lensing via cosmic strings in chapter 7. Here he says " Although a string does not exert gravitational attraction it affects the geometry of planes orthogonal to the string". Makes it sound as if they...

Thanks for all the help Tom Stoer,L.bloom. I think I have roughly got what you wanted to say.. would like to see how a spin two boson of QFT naturally leads to einstein's equations..Actually I had no idea that Feynman has a book on it, will surely look for it. Thanks. And can you please...

This may be a silly question since i am relatively new to the string theory. While going through a quantization of the bosonic string , I see a tower of states appearing corresponding to different modes of excitations of the bosonic string. Now I was trying to figure out how this whole machine...

I am confused about what area is being minimised in the nambu goto action..the one in the target space or the one in the parameter space? From Zwiebach's book I think he is trying to construct the area in target space and in the process we get derivatives with respect to parameters since each...

i see ..thanks.