# Search results

1. ### Best textbook or video or device for understanding QM

I absolutely found Dirac to have the best explanation of Dirac notation (Go figure!)
2. ### Too late for a 16 year old to pursue a career in Physics?

Let me just add: IT'S NEVER TOO LATE TO PURSUE YOUR PASSION I got a chemical engineering degree in 1978, and had a very satisfying career. In 2006, I decided I wanted to understand quantum mechanics, so I went back to school. I got a Schaum's outline for calculus (because I hadn't done calculus...
3. ### Dimensions of intensity

Homework Statement I know that intensity is power per unit area. When I do a dimensional analysis, it reduces down to mass per cubic time. Is there any physical significance to that? Homework Equations I=P/A The Attempt at a Solution
4. ### Leas squares curve fit problem

If your problem is that you have vectors x and y that contain your data, and you want to find A, B, C and D for the equation shown as a fit to that data, try the curve fitting toolbox. Run cftool, select x and y as your data set, then under fit select custom equation and you can enter the...
5. ### MATLAB Indicate mean with a bar in Matlab

Thanks for your help, but I could not get this to work because I am trying to change a .fig file in the property editor. I tried generating the code, and then making the modification there, but I was unable to save as .fig after that. Any suggestions?
6. ### MATLAB Indicate mean with a bar in Matlab

I want to put the following as an axis label on a plot, but I cannot figure out how to get the bar on top in Matlab \bar \xi Thanks.
7. ### Why is diffusion coefficient = 1/2?

Of course, now I get it! Thank you.
8. ### Why is diffusion coefficient = 1/2?

Thank you, but can you expand on your answer a bit? Not sure I understand what you mean in your second sentence.
9. ### Why is diffusion coefficient = 1/2?

Homework Statement I'm working with a 0ne-dimensional random walk and looking at Fick's second law, below. All I've read seems to take D = 1/2 as a given for ordinary diffusion, but where does this come from? Is there a way to derive it? Homework Equations \frac{\partial } {{\partial...
10. ### Function works on Windows but not Linux

Thanks to you both. Ultimately it was a path issue, although I thought I had checked that thoroughly before I posted.
11. ### Function works on Windows but not Linux

I downloaded largestcomponent.m today and it runs fine on my PC (Win 7 Enterprise SP 1) but when I try it on my Linux machine (Ubuntu 10.04 LTS) I get this message: ??? Undefined function or method 'largestcomponent' for input arguments of type 'double'. Even if I put the function file in...
12. ### MATLAB Matlab Legend Problem

I am trying to make a plot of four pairs of time series. The plot appears fine; I have two lines in each color as I want. The problem, in this case, is that the first two legend items both have red lines, and the second two both have black lines. I want each legend entry to match the color of...
13. ### Ordinary Diffusion and integration by parts

Thank you for your help, diazona. I still haven't completely wrapped my mind around probability densities yet. Nonetheless, with your suggestion (and some mathematical sleight of hand) I was able to satisfy myself that p(x,t) in the form of 2/x made the terms vanish as needed. A function that...
14. ### Ordinary Diffusion and integration by parts

I understand, of course, about the boundary terms. It seems to work out if I assume that p(0,t)=1 (ie, the particle(s) all start at the origin) and that p(\infty,t)=0 (there is nothing at the infinite boundary). This still leaves me multiplying zero times infinity, and isn't that considered to...
15. ### Ordinary Diffusion and integration by parts

Homework Statement For ordinary 1D diffusion show that the mean value of the square of the position is equal to 2Dt Homework Equations \left\langle {x^2 \left( t \right)} \right\rangle \equiv \int\limits_0^\infty {x^2 p\left( {x,t} \right)dx} \frac{\partial }{{\partial t}}p\left(...
16. ### Software to plot high quality figures

I use gnuplot to produce .eps figures. It's chief benefit is that it is free.
17. ### Discrete power law distributions

I'm not a mathematician, but I want to understand how a mathematician would view this issue. I'm working primarily with degree distributions for finite graphs, and when I make a log log plot of the frequency distribution the data points form a nice straight line (at least for low degree...
18. ### MATLAB Questions about plotyy in Matlab

Here is the relevant piece of code as it stands now: figure(2) [AX,H1,H2] = plotyy(plot2data(:,1),plot2data(:,2),plot2data(:,1),... plot2data(:,3)); set(get(AX(1),'Ylabel'),'String','Mean Value of C_{a}','Color','k') set(get(AX(2),'Ylabel'),'String','Mean Value of C_{b}','Color','k')...
19. ### Schools Going from industry to grad school

As you might expect, it depends on the school and what you did in industry. Overall, it's close to neutral. The pluses for the grad school are that they are getting a student who is a bit more mature - more committed and dependable. You will also come into grad school with practical knowledge...
20. ### Goodness of fit question

I am familiar with linear regression and the correlation coefficient. My current problem involves a data set that is pretty linear on a log-log plot. I have calculated the slope by taking logs of all my x's and y's, and doing the linear regression on the transformed data set. The resulting...
21. ### What is the significance of Fermi Temperature?

Homework Statement What is the significance of Fermi Temperature? Homework Equations I know it is the ratio of the Fermi energy (or the chemical potential at the Fermi energy) to the Boltzmann constant. The Attempt at a Solution What does it MEAN? I've worked out the Fermi...
22. ### LaTeX LaTex Problem

I hope you can help me with this problem. A few days ago, I began a post with a LaTex equation in it, but never completed the post (I got the answer I needed). I'm trying a new post today, and no matter how or what I enter as LaTex, when I preview the post I see the equation I tried to use a...
23. ### Question on tensor notation

Homework Statement Not a specific problem; I'm trying to understand what the notation means; I'm using primarily Griffiths, Marion and Jackson textbooks. The notation for a matrix, with the superscript row index and subscript column index I understand. For the EM field tensor, Griffiths...
24. ### Hertz's measurement of c

I would like to find a device to reproduce Hertz's experiment that demonstrated the transmission and reception of EM radiation. The equipment as I recall used a Leydan jar, an inductance coil to boost the voltage, a capacitor with a gap that sparked, and separately a ring with a small (I...
25. ### Hypersphere Volume - Fractional Dimensions

Well, I read that, but I don't really see what makes it so. I (sort of) followed the argument about why that produces the maximum volume, but what happens there? If it's some kind of discontinuity, what causes it?
26. ### Hypersphere Volume - Fractional Dimensions

Homework Statement I've completed the derivation of the hypersphere volume for integer dimensions, and my solution matches what's on Wikipedia. How can I generalize it to fractional dimensions? Homework Equations The Attempt at a Solution Not a clue; my only guess at this point...
27. ### MATLAB Matlab save/load question

I may have figured this out, which raised another question that I hope someone can answer for me. I had saved the variable in a file with the same name as the variable. However, I realized later that the file name was not exactly the same as the variable name, so I changed the file name...
28. ### MATLAB Matlab save/load question

I have calculated a variable called FNET. I have saved FNET to the hard drive using the following command: save(fullfile(BasePath,'FNET'),'FNET','-mat') BasePath is a string that gets the file to the correct directory on my hard drive. First Question: FNET shows up in the correct...
29. ### Understanding Jackson (again!)

Thanks; I went through again but with the full spherical harmonics, and paid careful attention to the primed and unprimed values, and got it, but it raises a more general question I would appreciate some help on. I know that azimuthal symmetry allows me to automatically set m=0, and I...
30. ### Understanding Jackson (again!)

Homework Statement Jackson Section 5.10, the uniformly magnetized sphere, I'm trying to fill in the steps from his first equation to Equation 5.104. I get the same potential except I am lacking the cos\theta term. My work shown below. Homework Equations The Attempt at a Solution...