Recent content by AuraCrystal

Using the conventions of http://www.damtp.cam.ac.uk/user/db275/Cosmology/Chapter4.pdf (not mine). For a flat FRW perturbed universe, the metric is can be written in general as: ds^2=a^2(\tau)[(1+2A)dt^2-B_idtdx^i-(\delta_{ij}+h_{ij})dx^idx^j] I understand intuitively that we can decompose Bi...

Yeah, but there's no spatial derivatives in \mathcal{H}_S^{'}

Against what? Time? Space? Both? :)

Yeah sorry. I keep forgetting the \mathcal. And yeah, all of the H's and L's refer to the Lagrangian and Hamiltonian densities.

Well, the idea is that the Hamiltonian is given by \mathcal{H}=\Sigma_i \pi_i \dot{\phi} - \mathcal{L}, and when we include interactions between \phi and A_\mu we get that it is the sum between the free K.G. Lagrangian, the free Maxwell Lagrangian, and the interaction Lagrangian I gave above...

Homework Statement Problem 7.15 from Aitchison and Hey, Volume I, 3rd Edition. Verify the forum (7.139) of the interaction Hamiltonian \mathcal{H_{S}^{'}}, in charged spin-0 electrodynamics. Equation 7.139 is \mathcal{H_{S}^{'}}= - \mathcal{L}_{int} - q^2 (A^0)^2 \phi^{\dagger} \phi...

Do you have any good references on Fourier transforms? Arfken/Weber doesn't talk about them all that much. :/

I am planning on working through Dodelson's cosmology book, but I find my knowledge of things like Bessel functions, Legendre polynomials, and Fourier transforms lacking. What're some good references for these things?

^Yeah, I forgot about that! Thanks! :)

Homework Statement Given the Lagrangian \mathcal{L}=\frac{1}{2} ( \partial_{\mu} \Phi)^2-\frac{1}{2}M^2 \Phi ^2 + \frac{1}{2} ( \partial_{\mu} \phi)^2-\frac{1}{2}M^2 \phi ^2-\mu \Phi \phi \phi, [The last term, the interaction term allows a \Phi particle to decay into 2 \phi particles...

I used Greiner's text on the electroweak theory and it was excellent. Taylor's classical mechanics text is also pretty good.

Hello, I was reading about big bang nucleosynthesis recently (If it helps, I'm using Mukhanov) and it was calculating the abundance of neutrons. It seems to say that X_n→X_n^{eq} (It says that X_n^{eq} is the equilibrium abundance of neutrons) as t→0. So...does that mean that the neutrons...

OK, I think I understand now. Thank you! :)

Oh I see. So we use it because it works? So the particle that couples to the U(1) is not the photon but another boson? And when mixed, it gives the photon and the Z boson? Does that have any relation to the fact that U(1) corresponds to weak hypercharge and not electric charge?

OK. So...what is B? And also, why do we enlarge the gauge group?