Reputation
58,845
Next tag badge:
144/100 score
18/20 answers
Badges
2 90 230
Newest
 Nice Answer
Impact
~790k people reached

Jul
6
comment Axis/Angle from rotation matrix
@Guesswhoitis. Regarding the paper, it seems that the referee observed what I would also say: that the basic idea behind the paper is well-known (and this also applies to my proof).
Jul
6
comment Implicit derivatives in one line. How do I do it?
I cannot understand the question at all. You may need a better english translation before posting here.
Jul
5
comment Axis/Angle from rotation matrix
OK - now I can say I have seen that paper... thanks for the link! I actually learned this in a mechanics lecture many years ago. But I never knew the history.
Jul
5
comment Animated Wave propagation using split operator method
I'm pretty sure that you can get this conservation law only if you integrate over all space, not locally at every point individually. It's the continuity equation.
Jul
5
comment How to calculate residues using different branches of the logarithm
@bbgodfrey OK, I've added an explanation.
Jul
5
comment How does Mathematica understand branchcuts of the complex logarithm?
If I understand you correctly, this is already included in my definition. You just have to change the angle $\sigma$ by $2\pi$. E.g., $\sigma=0$ and $\sigma=-2\pi$ are what I think you call continuous from above and below (I just don't think one should call this above and below because that's ambiguous for non-horizontal branch cuts).
Jul
5
comment Wrapping text around pasted graphic
I don't think Mathematica is a good platform for such tasks because it can't properly export to PDF, doesn't properly handle bibliographies, takes undue effort to make references to equations and figures, etc. I always tell people to use LyX instead. There, you can use the wrapfig inset to solve your issue. And unlike other $\LaTeX$ frontends, LyX supports direct pasting of graphics into the document.
Jul
5
comment Compilable function with the functionality of SingularValueList
Sure, I think there's a chance that may still give you a speed advantage. But as @Guesswhoitis. points out, SVD should probably be a last resort because it's so costly. In particular for square matrices (as you seem to have), other types of decomposition may also do what you need. That really depends on the application.
Jul
4
comment Compilable function with the functionality of SingularValueList
No, but you can perhaps speed things up by making sure all your matrices are numerical SparseArrays. See for example this Q&A which also mentions ToPackedArray in the Developer context. The loop over $n$ matrices is most likely not the bottleneck, so compiling it won't help.
Jul
3
comment Expand a product of operators
You can't use _ for subscripts. Instead, use f[1][x], etc. Maybe you can use this?
Jul
3
comment How does Mathematica understand branchcuts of the complex logarithm?
@Guesswhoitis. not sure what you mean. Do you want a multivalued function?
Jul
2
comment Is it possible that we can use “+” to add two vectors in polar form?
@ChipHurst The difference between phasor addition and AnglePath is that the angles there are relative rotations, which isn't the same as complex addition.
Jul
1
comment Switching ArcTan argument from a sequence to a list
Related: ArcTan and Compile
Jul
1
comment Multiple lines in an If statement
You should look up CompoundExpression in the docs, and the tutorial linked from that page.
Jul
1
comment Is there an elegant way of delaying evaluation of `A==B` when calling a function that uses this pattern
You should have a look at the tutorial.
Jun
30
comment Pull out scalars from NonCommutativeMultiply in commutator of SU2 spin algebra
Yes, if the individual spins are larger than 1/2, the part involving the Kronecker product would stay unchanged. As for replacing the Pauli matrices, one could perhaps benefit from using the Schwinger representation of arbitrary spins in terms of spin-1/2. Anyway, I admire your patience for $N=10$...
Jun
29
comment FullSimplify not giving me a physically useful answer for Mott scattering
I think you want this: With[{A=1/137,B=1,p=100},NIntegrate[\[Pi] A^2 (1-(B^2) (Sin[x/2])^2) (Sin[x])/(2 (p^2) (B^2) (Sin[x/2])^4),{z,0,750},{x,ArcTan[(600-z),155],ArcTan[(100-z),155]}]]/700 I.e., use NIntegrate and follow the advice of @rcollyer. Note the order of integration variables (outermost first).
Jun
29
comment Simplifying expression with non-commutating entries
@k_v If $[a,b]=0$, it follows that $[a,b^n]=[a^n,b]=0$, so this is not an issue.
Jun
29
comment How to solve time dependent coupled differential equations using Floquet method?
You're missing a Dot in the differential equation. What have you tried?
Jun
29
comment Pull out scalars from NonCommutativeMultiply in commutator of SU2 spin algebra
Yes, with those huge matrices it made a big difference to avoid the LinearSolve step. Fortunately, there is this orthogonality relation between Pauli matrices that makes that possible.