Recent content by cyc454

Hi Fowler! I think you can find the part of the answer in the pattern below (sorry but I had to use it, it is very useful and not so long :) ) : Small prelude: ## s'= s \sqrt{1-\frac{v^2}{c^2}} ##, where ##s'## is the distance measured in "moving" ref. frame (lets say your bro ref. frame)...

sorry, my mistake;) I am asking about ##\Lambda##---so Einstein thought that ##\rho## of our galaxy (which he considered our universe) is too small? That's why he put ##\Lambda## into his eq.? And how is it possible that non-empty universe with k=0 is flat? I thought that presence of matter...

soo... Did he put k=1 or what? Is ##\lambda## required in that case?

Hi, can you help mi understand Friedman equation with cosmological constant: \begin{equation} (\frac{\dot a}{a})^{2} - \frac{8\pi G \rho}{3}=-\frac{k}{a^2}+\frac{\Lambda}{3} \end{equation} I don't get it: Einstein wanted to get flat (##k=0##) and static (##(\frac{\dot a}{a})^{2}=0##) model with...

Well, we are integrating it over the entire R3.. I don't get it. There isn't any function depending on x. there is only P and W that depend on |x| or |xi+xj| PS I can't put P and W before the integrals, can I? PPS One more thing. There is a integral: ∫d3x1 and let's assume x1=x2+x3 so the...

if the xi=-xj then δ ≠0. ∫R3δ(x)d3x should be equal 1. Well, actually it should looks like this: ∫∞-∞δ(x)dx=1 but it is the same I thing.. This is all I know.

Hi! I've got a problem with an integral. Let's assume we've got something like this: ∫R3d3x1∫R3d3x2∫R3d3x3∫R3d3x4P(|x1|)P(|x3|)δ(x1+x2)δ(x3+x4)W(|x1+x2|)W(|x3+x4|) xi is a vector The "δ" is the Dirac delta. P(|x|i) & W(|xi+xj|) are some functions I would like to make it looks a bit...