# Search results

1. ### Simple time-independent non-degenerate quantum perturbation

I'm reading through this pdf (http://www.pa.msu.edu/~mmoore/TIPT.pdf) on simple quantum perturbation theory and I'm quite confused with equations 32 through 34. They have E_{n}^{(2)} = <n^{(0)}|V|n^{(1)}> = - \sum_{m \neq 0}{\frac{|V_{mn}|^{2}}{E_{mn}}} but I would have done E_{n}^{(2)} =...
2. ### Simple classic action integral

I'm trying to solve this simple problem (it's the first problem of Quantum Mechanics and Path Integrals by Feynman, I feel like an idiot not being able to do it....) It's just solving for the action, S, of a free particle (no potential, only kinetic energy..) So it should just be S =...
3. ### Series form of the Laplace transform

I thought it would be obvious, but I can't find a series representation of the Laplace transform. I'm looking for something analogous to the Fourier series and how it can be used to derive the Fourier transform. I though it would simply be f(x) = \sum_{s=-\infty}^{\infty}{C_{s} e^{sx}} , but...
4. ### Food labels - No magnesium mentioned

Recently I've been looking for foods rich in magnesium to experiment with personal nutrition. Although I had found several sources that sited the rich magnesium content of black beans, when I found several brands of the beans at the store, I noticed none of the nutritional labels mentioned...
5. ### Lie Symmetries Question

I'm currently reading a textbook on the application of Lie symmetries to differential equations (Symmetry Methods for Differential Equations: A Beginner's Guide Hydon, Peter. Cambridge University Press. 2000.) I'm somewhat at the beginning (pg. 22-25) where a method is being discussed to...
6. ### News Grover Norquist

Well, I've never started a political thread on the boards before, nor do I usually get involved in politics because of its persistently unscientific nature, but I feel this topic is of the most profound significance and thus a VERY worthy and eminent discussion. Many in the know would say that...
7. ### The logical fallacy of turning fact into opinion

Does anybody know of a term for the logical fallacy of attempting to soften the damage of a factual statement by trying to play it off as an opinion?
8. ### World History of Science

Does anybody know of some good books on world history specific to science topics? I'm looking for a good overview from the dawn of civilization to today, though I'd be content with a history that merely goes to the beginning of the 20th century. Currently my best candidate is this...
9. ### The Mathematics of Airfoil Design

My question is kind of simple, does the calculus of variations find its way into the design of the shape of an airfoil? I'm interested in what kind of mathematics gets used in basic airfoil design. I suspect the calculus of variations must be involved, but I know nothing about deriving the...
10. ### Why do we report the standard deviation of the mean in error analysis?

I've done a decent amount of reading on the subject, and I used this method of course when reporting errors during lab experience I got as an undergraduate, but it was never quite fully explained to me why exactly we report a value +/- the standard deviation of the mean as our result. Why not...
11. ### Number of photons in a mode (in a blackbody)

# of photons in a mode (in a blackbody) I've been going over a proof again concerning the thermal average number of photons in a mode of a cubical blackbody of length 'L' at equilibrium with a reservoir of temperature 'tau' (has a small hole in it, etc. etc. etc.) The logic went as usual...
12. ### Physics Physics buzzwords?

Hi everyone, I just graduated with my B.S. in Physics and I'm knee deep in the uncertainty of finding a (good) job with just a four year degree in physics. I'm currently writing my resume and people have told me that it should have more physics "buzzwords". This is probably because I am going...
13. ### In what way do we still not understand gravity?

I've always thought that Einstein's theory of general relativity was quite beautiful, it explained gravity as merely an intertial tendency of objects to move in straight lines (albeit different kinds of straight lines defined to be paths of greatest proper time) in a curved space-time. This...
14. ### Synchronized Bosons and Entropy.

How is it that the tendency for bosons to take the same state doesn't violate rules of entropy? I can understand why Bose-Einstein condensation wouldn't, because that's how the particles take a minimum energy state. I know lasers work because the photons present encourage other photon...
15. ### Best explanation for 1-way entropy?

What is the best explanation for why entropy must increase BY LAW. I can see it as being a good general rule, but I don't quite see why it's law, especially when you consider a micro-state explanation of entropy. What is the best argument for the law of increasing entropy?
16. ### The logic of information travel.

I was discussing with my E&M professor the idea of faster than light information exchange, which of course we found to be impossible, it didn't take much analysis of the simultaneity of events as seen by Einstein to realize that faster information travel than light would completely change the...
17. ### Low Temperature Diesel Fuel

Low Temperature Diesel Fuel (urgent) I'm having a problem with diesel fuel at the moment and would greatly appreciate insight into the subject. I'm currently stranded in Colorado where it's somewhere like -10 degrees (F) and our diesel truck isn't starting. I've narrowed down the problem to...
18. ### Physics After Physics B.S., looking to change directions

I'm obtaining a B.S. in Physics, but I'm thinking now that physics graduate school might not be the right thing for me. I'm interested in E.E. or computer controlled systems engineering, but I'm not sure how to correctly go about the change. Would I be capable of going directly into a graduate...