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Oct
22
comment Pull out scalars from NonCommutativeMultiply in commutator of SU2 spin algebra
I would do this without NonCommutativeMultiply altogether. But if you do want to go that route, I think you will have to provide the code that you tried for your commutator algebra. Otherwise we'd have to re-invent the wheel before answering.
Oct
21
comment Why doesn't FullSimplify simplify expressions with DiracDelta?
@NikkiBisschop I edited my answer to include more examples, and what I say in the first paragraph of the edit is based on your comment. It is in fact the answer to your overarching question why DiracDelta isn't simplified as such. One needs the information identifying the integration variable to make the correct simplification.
Oct
21
comment Why doesn't FullSimplify simplify expressions with DiracDelta?
@Dr.WolfgangHintze I just checked in version 8.0.4, and I cannot reproduce your problem. It simplifies correctly on my system, even in the older version. This is on Mac OS 10.7.5.
Oct
21
comment Why doesn't FullSimplify simplify expressions with DiracDelta?
@Dr.WolfgangHintze Ah, so this time it was good that I used version 10.0.1. There, it does simplify exactly to what you quoted...thanks for pointing out the issue with 8!
Oct
21
comment Why doesn't FullSimplify simplify expressions with DiracDelta?
@Dr.WolfgangHintze I did find a shortcoming when I switched the variables in your example and replaced the square by a symbolic n - see my edit. But I think one gets pretty decent results all in all.
Oct
21
comment Why doesn't FullSimplify simplify expressions with DiracDelta?
@Dr.WolfgangHintze Well, you get the correct answer. There is no problem at all. @Nikki Yes, the notation of the Dirac delta function is sometimes ambiguous because it doesn't include the info as to which variable is the integration variable. This can only be fixed by stating that information in the (Inverse)FourierTransform.
Oct
21
comment Why doesn't FullSimplify simplify expressions with DiracDelta?
@BobHanlon Yes, that's right, either way is fine (and if for some reason one way doesn't work, you can always try the other order to make sure).
Oct
20
comment Superscript prime symbol
Very closely related: How to Clear variables with apostrophe? There, I suggest using a different unicode glyph that looks better.
Oct
20
comment Derivative of an expression containing a symbolic sum
Yes, that's right.
Oct
19
comment Derivative of an expression containing a symbolic sum
@StripesPlaid Indeed, the last simplification works in Mathematica version 10.0.1, but not in version 8. I'm guessing you're using an older version. The TagSetDelayed rule for $\beta$ only gets applied in the 10.0.1 version after the derivative has been done under the sum. Then what the rule says is that whenever $\beta$ appears as the summation index without any additional range specification, and there is a Kronecker delta involving $\beta$, you're supposed to reduce the sum to the rest multiplying the delta.
Oct
19
comment Derivative of an expression containing a symbolic sum
This is probably a duplicate of how to differentiate formally. You only have to get rid of the Subscripts as variable names because they bury the meaning of the actual labels $\alpha$ and $\beta$ too deeply. Replace Subscript[lambda][alpha] by lambda[alpha] etc.
Oct
18
comment How to tell Eigensystem the type of the elements comprising a matrix I would like to diagonalize
@lagoa But that time is negligible compared to the computation of the eigensystem.
Oct
18
comment How to tell Eigensystem the type of the elements comprising a matrix I would like to diagonalize
It's not clear to me what you mean. Are you trying to find a symbolic solution first by using assumptions, or do you want to define a function that takes a numerical argument and returns the Eigensystem, or is M already numerical but written in terms of arbitrary-precision numbers, or something else? Please include a minimum example to clarify what you're trying to do.
Oct
16
comment Simplifying general solutions of differential equations (driven harmonic oscillator)
I really think the _C approach is unbeatable, so this should be the accepted answer. So I'll just leave it up to you if you want to mention Apart.
Oct
16
comment Simplifying general solutions of differential equations (driven harmonic oscillator)
The result of collecting over m is smaller, but not very systematic because m is a variable that could easily be eliminated from the entire problem. A more systematic way of getting that same result seems to be Simplify /@ Apart@Simplify[sol]. Here I use the fact that Map can also work on expressions that don't have head List - which is also something the OP could have used to avoid converting to List initially. But I think what the physicist expects is really the result of collecting over _C...
Oct
15
comment Simplifying general solutions of differential equations (driven harmonic oscillator)
This is a nice and general method for linear differential equations because the C[i] will always be multiplicative in front of the homogeneous solutions, so collecting them is the natural choice (+1).
Oct
14
comment 2D Fourier transform of a few (4) disjoint discs on a plane
@DumpsterDoofus I see, that's an interesting effect. I was using version 8 so I couldn't see that directly at the time.
Oct
14
comment 2D Fourier transform of a few (4) disjoint discs on a plane
@DumpsterDoofus (+1) In case anyone wants to reproduce the plot in a Mathematica version that doesn't have TensorProduct yet, it's also possible to just do the monochrome image first and then wrap it in Colorize[%, ColorFunction -> (Blend[{Black, RGBColor[1.0, 0.3, 0.1]}, #] &)].
Oct
13
comment How can I create a plot like this in mathematica?
There's also BoxWhiskerChart
Oct
12
comment How to create a reliable natural integral operator?
I voted to close as a duplicate originally, but it may be better to close because it's unclear what the question is asking. "Natural integral" is not a thing.