Recent content by alsey42147

basically the interesting properties of QCD exist because the gluons interact with each other. one of these properties is that the strong force becomes stronger with increasing distance, or equivalently, with decreasing energy. in a nucleus you have relatively low energies/large distances, so...

well, i am still confused. looking at some textbooks, they all state that C(gamma) = -1 since the EM field is produced by charges that change sign under C transformation. fine. they then say that because the neutral pion decays to two photons, it has C = +1. if the C number of the neutral pion...

ok, i was being retarded, as i expected. the pi0 is C = +1 and the photon is C = -1, and C must be conserved in EM interactions. I'm fairly sure someone taught me that at some point but i'd completely forgotten.

if the momentum of the B is large (in the lab frame) then the decay products are boosted and hence have small transverse momentum relative to the B momentum. a B is quite a heavy hadron so this boost effect is smaller than in a light flavour jet, which is why b jets are generally broader than...

hi, yesterday i had a discussion with some friends about the decays of pions which produced a few questions that we couldn't resolve properly. if anyone can shed some light on this matter, or point out flaws in the reasoning below, that would be great. so starting with the decay of a neutral...

i'm a bit confused about the currents in the expression for a matrix element for an interaction... e.g. you could have a current like (adjoint spinor)x(spinor) which is scalar, this makes sense to me. or you could have a current like (adjoint spinor)x(gamma matrix)x(spinor) which is vector...

I just read this: http://www.americanchronicle.com/articles/50304 I'm just wondering what those who are more knowledgeable about this stuff think of it. My guess is the arguments are invalid otherwise people wouldn't bother studying string theory... Do gravitons interact with...

so, i have a few interviews for PhDs in particle physics over the next month and I'm looking for some information on what generally happens at a PhD interview. If anyone would like to share their experiences, interviewers or interviewees, i would greatly appreciate it. I'm not too worried...

you did, thanks!

right, so de broglie waves are kind of an obsolete concept? is the de broglie wavelength then just the wavelength of a wave which the particle behaves like, but that wave doesn't actually exist as something physical?

so quantum mechanics doesn't actually tell you what particles are or what they do? you just have a wavefunction from which you can get probabilities that have some relation to real measurement? lol, everyone i ask about this tells me the same thing. is this because no one actually knows? i...

so now I'm finally getting to grips with the maths of quantum mechanics, I'm getting really confused about what it means physically. sorry this is quite long but it seems like the more i think about quantum mechanics, the more my understanding of it disintegrates. first, does quantum mechanics...

awesome, thanks. and yes B is constant.

damn, i wish i was more proficient with matrices and stuff. i might have to do a bit of quick revision. the equation is just electron motion in a magnetic field without the constants. my friend says that from the equation d^2x/dt^2 + (dy/dt)|B| = 0 you just integrate to get dx/dt + y|B| =...

ok, i don't know what to do with something like this: (d^2R/dt^2 ) + (dR/dt) x B = 0 where the capitals are vectors (sorry i suck at latex). R is a position vector in x-y plane and B is in the z-direction. do i split this into equations for x and y directions separately and solve them...