# Recent content by guest1234

1. ### I About Lie group product ($U(1)\times U(1)$ ex.)

I recently got confused about Lie group products. Say, I have a group U(1)\times U(1)'. Is this group reducible into two U(1)'s, i.e. possible to resepent with a matrix \rho(U(1)\times U(1)')=\rho_{1}(U(1))\oplus\rho_{1}(U(1)')=e^{i\theta_{1}}\oplus e^{i\theta_{2}}=\begin{pmatrix}e^{i\theta_{1}}...
2. ### What function I'm looking at?

For some reason your response led me to think that the answer is obvious... :biggrin: So I plotted 1-e^{-x} and it turns out that it's the answer I'm looking for. Never seen an (inverse or whatever it's called) exponential decay plot in log-log scale before .. As for the irrelevant 'where did...
3. ### What function I'm looking at?

Hey all What's could the function be on the plot (see the attachment)?
4. ### Mass dimension of coupling constant -- always an integer?

Well I was thinking whether it'd be pseudoscalar (that shouldn't be any big problem -- if we really want a parity violating theory). I just thought about gauge transformations, and yup, you were right -- the term wouldn't transform as a (pseudo)scalar but as a spinor. Adding scalar and spinor...
5. ### Mass dimension of coupling constant -- always an integer?

Thinking beyond SM, what are the physical consequences if the Lagrangian contains an interaction term with an odd number (i.e. only one) of fermions?
6. ### Mass dimension of coupling constant -- always an integer?

Just a simple question -- can the dimension of coupling constant be a rational number or should it always be an integer? The question arose when I was trying to construct a Lagrangian with an interaction term involving two spin-1 particles and a fermion. The dimensions add up to 7/2, which...
7. ### Momentum space measure -- change of variables

I'm working through an article called "Cosmic abundances of stable particles -- improved analysis" (link -- viewable only in Firefox afaik), the result of which, equation (3.8), is cited quite a lot. I'm more interested in how they arrived there. Particularly, how come momentum space measure...
8. ### Feynman rules - where do the imaginary numbers come from?

I'm trying to learn how to derive Feynman rules (what else to do during xmas, lol). The book I'm using is QFT 2nd ed by Mandl&Shaw. On p 428 they're trying to show how to derive a Feynman rule for W W^\dagger Z^2 interaction term g^2 \cos^2\theta_W\left[W_\alpha W_\beta^\dagger Z^\alpha Z^\beta...
9. ### Relative velocity of beams

doh... natural units... thx
10. ### Relative velocity of beams

How come relative velocity of the beams can be expressed by v_{12} = \left| \vec{v}_1 - \vec{v}_2 \right| = \left|\frac{\vec{p}_1}{E_1} - \frac{\vec{p}_2}{E_2}\right| where \vec{p}_{1,2} and E_{1,2} is the momenta and energies of incoming particles, respectively? Similar equation is in Peskin &...
11. ### Plane wave expansion of massive vector boson

So... I think I'll go with two sets of ladder operators as usual in complex scalar field/fermions. It seems that the thesis uses them implicitly -- in Wick contraction the other operator is neglected because of the normal ordering requirement. About path integral.. thanks but I'll skip it for...
12. ### Plane wave expansion of massive vector boson

I'm trying to derive Feynman rules for massive vector boson and its antiparticle. It all boils down to plane wave expansion of the bosons which atm is a little bit confusing. Should I account for two different set of ladder operators (as in the case of complex KG or spinors, cf Peskin&Schröder...
13. ### UDP multiclient server in C

Hi all I'm trying to create a server that uses UDP and is capable of handling multiple clients. The server should 'stream' content to the clients only on the initial request (i.e. when starting the client). The general idea is to test how many clients is the server able to 'serve' before the...
14. ### Dual tensors in Lagrangian

Yeah, I forgot to mention I'm interested in U(1) theory. Thanks for the link, will read it.
15. ### Dual tensors in Lagrangian

Thanks, Bill_K, I didn't know that before. A quick proof for the eager: \begin{align*}\widetilde{F}^{\mu\nu}\widetilde{F}_{\mu\nu} &= \frac{1}{4}\epsilon^{\mu\nu\rho\sigma}\epsilon_{\mu\nu\alpha\beta}F_{ \rho \sigma}F^{\alpha\beta} = \frac{1}{2}\delta_{\alpha...