Recent content by tshafer

I'm working through Srednicki's QFT text, and I'm continuously vexed by the various numerical factors in diagrams and vertices, as well as the grouping of diagrams. For example, in Chapter 10 (pg 75) Srednicki treats basic \phi\phi\rightarrow\phi\phi scattering processes in \phi^3. He claims...

While deriving the Helmholtz Green function in Sakurai we come across the integral \int_{-\infty}^{\infty}q\,dq\,\frac{e^{iq|\vec x-\vec x'|}-e^{-iq|\vec x-\vec x'|}}{q^2-k^2\mp i\varepsilon'} This equation has poles at q \simeq \pm k\pm i\varepsilon', however when doing the residue calculation...

Thanks — I thought so, too, but this is my first serious exposure to parity or discrete symmetries at all. I'm making an attempt at trying to actually understand it rather than just floating along.

The statement is along the lines of "For commuting H and P, if H is degenerate its eigenkets do not have definite parity." i.e. there is room for wiggling out of this due to degeneracy. We also talked about the double-well potential in the context of symmetry breaking... but I don't claim to...

We're working on the parity operator in my second semester quantum mechanics class and there is one point I am confused about, either in the definition of degeneracy or in the parity operator itself. We talked about a theorem whereby the parity operator and the Hamiltonian cannot share...

Great, thanks! It's things like this that I really should have nailed down by now... but better to get it now than right before the written exam, I suppose.

It would have to point from =Q to -Q (outward radial), no? That's why I'm confused... I could take the absolute value to get the correct value for the capacitance but still... maybe it's confusion in calculating capacitance? As best practice should one always do the integration against the...

I'm calculating the capacitance of a set of spherical shells of radii b > a. To do this, I place a charge +Q on the inner shell and -Q on the outer shell so that I get the electric field vector pointing outward \vec E = \frac{Q}{4\pi\varepsilon_0} \frac{\hat r}{r^2}. Finding the...

Homework Statement We have a hoop of radius r and mass m resting on a cylinder of radius R which rolls without slipping on the cylinder under the influence of gravity. If the hoop begins rolling from rest at the top of the cylinder, at what point does the hoop fall off of the cylinder...

That's what I thought, too, but I was unsure. Trying to de-rust, here, heh.

Homework Statement Under what conditions may I change temporal and spatial derivatives? I cannot remember for the life of me. EG: \frac{\partial }{\partial t}\left( \nabla \cdot \mathbf{A} \right) = \nabla \cdot \left( \frac{\partial \mathbf{A}}{\partial t}\right) Thanks.

For what it's worth, I was very impressed when I visited N.C. State's department - nice people, nice facilities, and $$. Having said that, I'm headed to Chapel Hill. :D Tom

I agree... some of the problems are probably out of reach in your context, but the book is very well written.

Apparently the PGRE isn't everything... I got into UNC Chapel Hill for HEP Theory/Gravitation today! :biggrin:

One problem I'm having is keeping mine neat and orderly. I'm unclear if I should clearly separate paragraphs on why I want to go on to graduate school from why I am qualified... or if I should clearly separate why I am qualified from what my research interests are. I think I am now thinking...