Recent content by Jerbearrrrrr

Hi, it says on Wikipedia here that "a particle in state n, and a particle in state m" is described by |n>|m>±|m>|n> rather than the naive |n>|m>. I can see why this is sensible on many accounts (eg, you'd want to preserve the predicted probability of finding blah under switching the...

Hi, could someone please link me to the relevant theorems etc (or explain personally) that answer the issue that follows. Say you have an ODE (let's say 2nd order for now). Let's look for a power series solution (ie assume we're engineers). So, we write out a couple of sigmas etc and sub...

Thanks. I thought they were after something like that. Expand sin(A+B) and wave some hands. Kinda just looking for a definition of 'rotation' in the context of "mathematics for engineers" I suppose, since my friend (whom I'm posting on behalf of) couldn't supply one from lecture notes. To...

An engineer came to me with the following problem Homework Statement Suppose y = A x where x,y \in R^2 and A = \left( \begin{array}{cc} \cos \theta & -\sin \theta\\ \sin \theta & \cos \theta \end{array} \right) . Show that y is an anticlockwise rotation of x about the origin. Homework...

dV/dt := 600 - 1.5V So dV/dt = 0 at V=400. Some water must accumulate in the tank. Intuitively, because V=0 (initially) gives dV/dt > 0 (and we can integrate a strict inequality happily). Maybe it's not a stable equilibrium, but won't all scenarios always end up at V=400? Like some kind of...

An engineer came to me with the following problem. I'm not convinced the problem is correct - but I've probably just overlooked something, since I haven't done any vaguely practical problems in years. Anyway, here it is. Homework Statement...

Hi, I'm trying to learn some geometry. I'm a maths graduate but didn't take any differential geometry. I did take a GR course, and now want to learn the 'proper' geometry theory that underlies some of the ideas. Does anyone have any good resources (videos, or lecture notes) that they can...

I think it means that too. Btw, it was a programming exercise. So it's "Write a program that ___".

Good point, Proton Soup. But it's hard to say for sure if the 1 is like...precisely "inclusive". Also I think only one of each weight can be used. Also, a good mathematician would make it clear >: (using the most dull and possibly repetitive language possible)

This isn't even my homework, but I'm disagreeing on a friend on what it's asking. Dunno what forum to ask it in lol, sorry. "Using only different combinations of those variables and the addition and subtraction operators, print all the positive weights that can be measured with 9, 3, and 1...

Sorry to resurrect the thread, but it'd probably be worse to make a new one. Thanks for the replies. But I'm still not seeing the significance of the quantity 'E', other than in an expansion, one term just happens to be the kinetic energy. Not sure how to explain what I don't understand but...

Yeah I just saw it on TV, on QI a second ago. Not the gospel truth necessarily, but it's meant to be a programme that looks for counter-intuitive truths (somewhat in the sense of mythbusters). It's quite high profile in the UK, but granted, doesn't have any bearing on its validity. Anyway, I...

When you read to yourself, say for leisure (not reading physics or mathematics for example) or in 'ordinary circumstances', do you hear each word in your head? I think I might just be a retard, but it turns out that I'm skim-reading if and only if I don't 'hear the words in my head'...

[PLAIN]http://img46.imageshack.us/img46/1699/dsfadsfas.png The formula holds in the rest frame. Why is this particular extension 'the' extension? (Context is Electrodynamics/SR. It's just a piddly 16 lecture course that outlines Electrodynamics and SR and a bit of Quantum phenomena at the end...

What effect does switching the signature have, from the perspective of calculation? Would it switch covariant with contravariant? The fields derived should be invariant surely, since it's just two ways of representing the same physical thing?