Recent content by joriarty

Thanks for your help Dickfore. I'm not sure where your first expression comes from. I suppose Aa(r) is f(r), but what is xa? Thus, I'm having trouble seeing how to apply that to where you've broken down the Poisson brackets by linearity (I see that the first and last terms there are zero...

I'm struggling to understand Poisson brackets a little here... excerpt from some notes: I am, however, stumped on how this Poisson bracket has been computed. I presume ra and Aa(r) are my canonical coordinates, and I have \dot{r}_a = p_a - \frac{e}{c}A_a (r) with A_a = \frac{1}{2}\epsilon...

Voila, that bell curve normalisation works! Obvious answer once I read the Wikipedia article on the Gaussian integral (which I had long since forgotten if I had ever learned about it before) He hasn't talked much about the dirac delta function in class (partly why me and my mates are having...

I have an unusual question, though hopefully someone here can answer it. Apologies if this belongs in the homework forums, not really sure where to put it, as I'm not asking for help with the problems here. I'm currently in the second half of a 12-week third-year University course on PDEs. I...

Got it! Thanks :)

Shouldn't that be u(0,0) = C1*C2*sin(0) + C1*C3 = 0 ? C2 and C3 could be anything but I think this restricts C1 to being zero.

Thanks for your reply. I'm not familiar with the term "triangular" - I presume this simply means that the temperature gradient between 0 < x < L/2 is uniform? Which would make it easy enough to get the temperature for any x at t = 0. Also, I agree that having C1 or C3 equal to zero isn't very...

See attached image for the question and my working. Hopefully you can read it OK, I had to resize it to fit to the allowed dimensions. I'm unsure how to proceed or if I have done something wrong previously - the initial and boundary conditions are tripping me up. The boundary conditions in red...

Homework Statement The diagram below shows two circuits: a very long straight wire, and a single loop rectangle of dimensions a and b. The rectangle lies in a plane through the wire and is placed a distance c from the long wire as shown. The long straight wire carries a current of I...

Ah, I get it now. Thanks guys

I'm still not getting it. Plotting f(t) I get a series of step functions as expected where f(t) = 1 from t = 0 to pi (ie where n = 0), zero from pi to 2*pi (ie where n = 1), one from 2*pi to 3*pi (n = 2) and so on. But I don't see how this infinite series can be equated to 1 - H(t - pi) which...

I'm revising my course text for my exam and came across a Fourier series problem finding the Fourier series of the square wave: http://img574.imageshack.us/img574/5862/eq1.png. It is then calculated that the complex Fourier coefficients are...

I'm not sure what you're trying to say there, beyond restating the initial problem. I just managed to figure it out anyway, I had an 'n' in there that should have been an 'N'. Problem solved, assignment done :D

Show that [PLAIN]http://img829.imageshack.us/img829/3411/screenshot20101011at115.png I really don't know where to start with this. It is the very last question of an assignment on Fourier series and the Gibbs Phenomenon, if that is relevant I can give more details but I don't think it is...

This question has been bugging me... I've rephrased the question a bit so it shouldn't require much astrophysics knowledge to understand, just a bit of regular physics. Consider a binary star system. By doing some geometry based on visual observations of the positions of the two stars over...