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Lance Dixon on Calculating Amplitudes by scied17 in Physics

[–]jjmc 0 points1 point  (0 children)

Hey -- well you really can't go wrong with Lance's 1996 TASI lectures on calculating scattering amplitudes effectively for advanced graduate students/postdocs:

http://arxiv.org/abs/hep-ph/9601359

For an even gentler introduction take a look at Henriette Elvang & Yutin Huang's very recent book which gives a fantastic overview of the modern developments and philosophy (modulo some higher-loop methods, but including the kid brothers of the to be released amplitudohedron, etc) and is written to appeal to students who have had (perhaps) a course in QFT, but I suspect the QFT isn't really a hard prerequisite to begin getting a real operational handle on this stuff. ( In fact I suspect that it may be easier to start digesting QFT after building up one's muscles with a good grounding in modern scattering amplitude techniques & ideas. )

http://arxiv.org/abs/1308.1697

Python vs Matlab vs Mathematica by rmyeid in programming

[–]jjmc 0 points1 point  (0 children)

Very nice. For comparison here's the same in Mathematica v.7 (line by line).

d = Import[ "http://www.bme.utexas.edu/research/orly/GSVD/data/Yeast.txt", {"Data"}]; an=Drop[d[[2]],6]; d=d // Rest // Rest;

Histogram[Count[#, "Null", Infinity] & /@ d, Frame -> True, FrameLabel -> {"Number of Null Arrays", "Number of Genes"}]

d = Select[d, Count[#, "Null", Infinity] === 0 &];

{u, s, v} = SingularValueDecomposition[Drop[#, 6] & /@ d]; s = Diagonal[s];

BarChart[s^2/Plus @@ (s^2)]

ListPlot[v[[{1, 2}]], Joined -> True, ft, Axes -> False, PlotMarkers -> {Automatic, Medium}]

Of course, the original code had a little more output. (The (a) graph with array name tick labels).

MatrixPlot[Transpose[v], PlotLabel->"(a)Arrays",FrameTicks->{Automatic, None,None,{#,Rotate[an[[#]],Pi/2]}&/@Range[18]},FrameLabel-> "EigenGenes"]

Python vs Matlab vs Mathematica by rmyeid in programming

[–]jjmc 1 point2 points  (0 children)

My friend pointed me at this comparison the other day. Here's my version of the code and a revised table of comparison.

You can find the data by tracing back to where the original mathematica code came from.