Recent content by Zak

If say you have some scalar field, θ(x^u), where x^u represents the 4-vector coordinates of spacetime, and then the typical classical equation of motion, a = -∇θ, how would one go about 'generalizing' this to a relativistic version? Since F = ma, would you have to write it as d/dt (P^u)...

Hello! I'm trying to derive the linear velocity vector from the position vector and the angular momentum vector. I've seen on the internet that V = W x R (V,W and R are all vectors and x is the cross product) but I cannot for the life of me derive it! I've tried doing it by writing out the...

Hi! I have a problem: I need to solve an equation, Ax=y, where A is a known matrix, y is a known column vector and x is an unknown column vector. Unfortunately, A is singular so I cannot do the simple solution of inverse(A)*y=x. Does anybody know of any way that I can obtain the coefficients...

Essentially, I'm wondering (knowing virtually nothing at present), what is at the front of modern research in the realm of energy. Whether this be renewable energy, or simply more efficient ways of using energy (e.g. fuel cells?). I assume nuclear fusion will be mentioned too, so what obstacles...

(precursor: I have not formally studied GR) I have noticed that the gravitational constant found in classical gravitation is also used in GR. Why is this the case? Am I correct in thinking that the constant was determined by Cavendish and was for the classical theory of gravitation? So, my...

Ah yes I think that makes a lot of sense! So does this mean that the statement 'H(0,1a,1b) = H(0,1) + P(1)H(1a,1b)' is in a sense saying that after a very large number of repetitions (on average), the number of bits required to express all possible sequences is equal to the average number of...

I am reading a book called 'quantum processes systems and information' and in the beggining a basic idea of information is set out in the following way. If information is coded in 'bits', each of which have two possible states, then the number of possible different messages/'values' that can be...

Ah, I think then I will have to learn more about Quantum Mechanics to really even appreciate the question. Thanks

There have been many posts requesting a quantum mechanical explanation for the refraction of light through glass, but none of them (as far as I'm aware) explain why higher frequency light refracts more than lower frequency. Can anybody explain why?

my bad, I meant to say the description wasn't very good. So does anybody have a better explanation for why two charges would attract each other in relation to the photon exchanges between them?

this sort of summarises it, though the description is great http://voyager.egglescliffe.org.uk/physics/particles/parts/parts1.html

I have read some fairly vague descriptions of charge that say it can be looked at as the amplitude for a particle to exchange a photon. For example, when two electrons repel, it is because a photon is emitted from one too the other, which would change the direction of both equally and...

I understand mathematically etc how light can doppler shift when looked at as a wave but can it be understood how light doppler shifts as a photon i.e. could just one photon be doppler shifted? For example; Say there is an atom with energy levels 1 and 2. One observer, stationary relative to...

Ah ok, so then what are the conditions that allow pair production? also, surely if the particles traveled forward diagonally, the net momentum would not be zero as there would be a net 'positive' momentum in, say, the y-axis but not the x hence the initiall momentum of the photon traveling...

Just a thought... Say that a stationary (relative to me) source of light emits a photon with the energy level (as observed by me) appropriate to pair produce an electron-positron pair. Meanwhile, a second observer travels towards the light source, thus blue-shifting the light, and hence...