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Aug
7
answered How to sort my list?
Aug
7
answered How to integrate a function which is only known at discrete points
Aug
5
comment Matrix containing ellipse
Doesn't MorphologicalComponents[ Rasterize[Graphics[Disk[{0, 0}, {2, 1}]], ImageSize -> 800]] give a matrix?
Aug
4
comment How to make Eigensystem in version 10 produce the same results as version 9
@xslittlegrass right, I know the closed form solution from the papers I cited (that's where I first saw them, but I am not sure if they first appeared elsewhere). If you're interested in general potentials and/or time dependent solutions then you indeed have to do it this way (numerically). As to how I knew it, I guess it's like asking "wow how did you know this is the Schrodinger equation?" isn't it? Now, if you had an interacting Hamiltonian and I spotted the potential, that would have indeed been noteworthy :)
Aug
4
comment How to make Eigensystem in version 10 produce the same results as version 9
Actually, your Hamiltonian is literally that of a SHO on a 1d lattice (plus noise). You can find analytical solutions to this here or here, although I'm not sure how useful they are to you.
Aug
4
comment How to make Eigensystem in version 10 produce the same results as version 9
@Jens I think here it really is due to degeneracies. It would have been useful to have a canonical question and answer to this somewhere.
Aug
4
comment How to make Eigensystem in version 10 produce the same results as version 9
You Hamiltonian has degenerate eigenvalues, see here. I am guessing this is a single particle in a harmonic oscillator potential (ListPlot[Diagonal[Chop@Hmtx]]), in which case the degeneracy is physically due to the reflection symmetry of the potential. If you plot the absolute value of the eigenvectors (the density) you'll see what is going on and why hybridisation is so weak.
Aug
3
comment Problem setting up C compiler on a Mac
@TedErsek You can most certainly write C programs for OSX (or any other language for which you have a compiler). XCode is an IDE, which is meant to help with writing code. It's focussed on objective C and C, but supports other languages. Now, you seem to have clang installed in the usual place, so there is some misconfiguration in mma itself. Does Compile[{{z, _Real, 1}}, Sin[z], CompilationTarget -> "C"] also return $Failed?
Jul
30
comment Best practice to group and have your favorite custom functions available at startup
I suppose you are aware of init.m and are asking for the best way to organise your functions beyond that?
Jul
28
comment Sum with Levi-Civita
@Dave84 since you have explicit values for the $a,b,c$ you can use TensorProduct
Jul
28
comment Sum with Levi-Civita
It looks like LeviCivitaTensor, not LeviCivita. Also the code you give has syntax errors, and even if it didn't it doesn't work because a and so on aren't defined and when you try to retrieve their elements, you get an error. Not to put too fine a point on it, but you need to look at the docs.
Jul
28
comment Is there a function for nearest power of 2 in Mathematica like nextpow2 in MATLAB?
Ceiling[Log[2, #]] &
Jul
25
comment Ordering oscillators with negative powers: Infinite loops
Can't you try to isolate which rule is the problem? It seems unlikely that anybody will sit down and work it out from your mass of patterns! Try to put yourself in the answerer's position.
Jul
25
comment Ordering oscillators with negative powers: Infinite loops
Can you isolate and post the bit of code that results in an infinite loop? I don't see why normal ordering according to your prescription would result in an infinite loop.
Jul
23
comment Is there a way to recreate the typical Red/Blue-Postereffect using Mathematica?
@RahulNarain truth be told, I did try improving them and got bored after 20s. So I understand you (but I'll hold on to those sweet upvotes anyway)
Jul
23
revised Is there a way to recreate the typical Red/Blue-Postereffect using Mathematica?
added 42 characters in body
Jul
23
revised Error message: Coordinate index 0 is out of range for the enclosing GraphicsComplex
added data to question
Jul
23
comment Is there a way to recreate the typical Red/Blue-Postereffect using Mathematica?
@eldo the comment above was for you
Jul
23
comment Is there a way to recreate the typical Red/Blue-Postereffect using Mathematica?
complaints should be addressed to @RahulNarain who came up with the colours. I'm just here to collect the votes :)
Jul
23
answered Is there a way to recreate the typical Red/Blue-Postereffect using Mathematica?