Recent content by Plaetean

Thanks for replying - just in case anyone else ends up with the problem I think I may have found a workaround. So the error results from the fact that there are undefined variable in the code - I have simply removed troublesome variables and corresponding if statement from the code, and they do...

So this is a pretty specific technical question - but if anyone has experience running the N-body simulation GADGET2, I'm generating initial conditions using N-GenIC, and trying to turn on gas particles in the makefile gives the same error as described here...

Homework Statement I need to gauge the symmetry: \phi \rightarrow \phi + a(x) for the Lagrangian: L=\partial_\mu\phi\partial^\mu\phi Homework EquationsThe Attempt at a Solution We did this in class for the Dirac equation with a phase transformation and I understood the method, but...

Thanks for this - its kind of bizarre that I have never come across this kind of thing explicitly in my courses, and I'm finding it really hard to find clear online material on it as well.

Bump!

Homework Statement Working through problems in Mahan's 'Many Particle Physics' book, and at the end of the 1st chapter there's a question where we're asked to consider a fermion system with three energy states with eigenvalues E1, E2, E3, and matrix elements M12, M23, M13 which connect them and...

I'm working through some intro QFT using Peskin accompanied by David Tong's notes, and have a question over notation. From Peskin I have: x^\mu=x^0+x^1+x^2+x^3=(t,\mathbf{x}) and x_\mu=g^{\mu\nu}x^\nu=x^0-x^1-x^2-x^3=(t,-\mathbf{x}) so p_\mu p^\mu=g^{\mu\nu}p^\mu p^\nu=E^2-|\mathbf{p}|^2...

Homework Statement http://i.imgur.com/BV5gR8q.png Homework Equations d/dx ∂F/∂y'=∂F/∂y The Attempt at a Solution I have no problem with the first bit, but the second bit is where I get stuck. Since the question says the speed is proportional to distance, I have taken v(x)=cx where c is some...

Thank you!

My notes say: http://i.imgur.com/Z0v7Psi.png The particular part I don't understand is that we know I = 1, and the text says: for S = 1, I can be equal to 1 for L = 0, 1, 2.If we know I = 1 and S = 1, how can L be anything other than 0? Thanks as always!

Excellent, thank you very much, that makes sense now. So the operator can change the basis vectors themselves?

Because different states are orthogonal, so ##\langle \phi_n | \phi_m \rangle = 0## for ## m\neq n##

Could you elaborate a bit?

In my course notes for atomic physics, looking at time independent perturbation for the non-degenerate case, we have the following: http://i.imgur.com/ao4ughk.png However I am confused about the equation 5.1.6. We know that < phi n | phi m > = 0 for n =/= m, so shouldn't this mean that < phi n...

No, perhaps I could do it just using Gauss' law instead, might be easier