Recent content by bardeen

Sorry I don't think I'm getting it. What would the expression for the envelope be?

But then, is there a group velocity to the whole thing? The first two terms you wrote have a group velocity Δω/Δk, and the last one is just a plane wave. But what is the group velocity of all three terms put together?

You get two terms of the same form as in the usual case. So, you get something like: envelope1*(sine wave) + envelope2*(cosine wave) Is the group velocity still delta omega/ delta k ? That's what my instinct told me but I somehow feel it's not right...

Hi all, I understand the concept of group velocity when applied to superimposed sine waves of the same amplitude, and even when applied to wave packets (in which case you get the well-known expression ∂ω/∂k). My question is what happens when you add two sine waves of different amplitudes? So...

And I have never understood why physics departments do so much advertising for physics. Why do they want more and more physics PhDs if there aren't enough appropriate jobs for them? I don't think the field would die if not for their advertising, since there will always be people that go into...

You guys are right. I guess I would just be kind of pissed because of all the build up and then nothing. But yeah I get it. :)

I was out on vacation for a couple of weeks. Ever since I came back I haven't seen her again. Maybe she is out of town too? Hopefully I will see her again when the fall semester starts in 2 weeks or so. I am braver now. I will do it. If she has a bf I will be very mad.

Thanks all! I'm more motivated to carry on! One more thing... how does one date while doing a PhD? It's really tough since it's almost all guys in physics grad school and it's hard to find the time to go out and meet girls. Any suggestions? I'm looking for a wife-material type of girl :)

(or tell me whatever your opinion is) I am in my second summer as a graduate student and have reached a point where I am questioning all my decisions. I used to think that what was most important in my professional life was that I be doing something I loved (and that it at least payed...

Wow I'm amazed at the great input. I was expecting more dull stuff to be honest but you guys are real romantics. I don't know if I have the courage to pull off the note thing, I was thinking just saying something casually. The problem is that I don't know how you're supposed to keep a...

There's this cute girl I constantly see at my university library. I would like to meet her but I'm scared of interrupting her. She seems so focused on her stuff and the library is really quiet so I feel weird approaching her. I tried to peak at what she was working on and all I could see were a...

Hello all, Suppose I want to find all publications by X author. What is the best way to do this? I am overwhelmed by all the options out there. Also, how does it all work? What I mean by this is, when you publish something, say in Phys. Rev., does Web of Knowledge and Arxiv get automatically...

Thank you, that was very helpful. When you have an up electron and a down electron, the total spin can either be 1 or 0. I'm having trouble understanding this. If one is pointing up and the other pointing down, why isn't the total spin just 0 everytime?

This is a pretty basic question I believe. When you describe the state of a single particle, let's say its spin state, it can be in a superposition of different states (like up and down). When you do a measurement of its spin you'll either get up or down, since its spin state will collapse into...

Thank you guys, that helped :)