Changes between Version 7 and Version 8 of DevelopmentPage/MultiParton

Timestamp:

Feb 21, 2010, 8:25:52 PM (14 years ago)

Author:

Fabio Maltoni

Comment:

--

DevelopmentPage/MultiParton

@@ -26 +26 @@
 At the end this is slower that the current way madgraph does because one ends up in calculating many times the same
 diagrams, i.e. this is inefficient. 
+Note that a jamp is a color ordered amplitude and could be directly computed by mg5 by keeping the order of the gluons fixed in the diagrams.
 
 === Second Step : getting the code faster. ===
 
-I believe the recalculation of the sigrams could be avoided with some clever caching, even though
+I believe the recalculation of the diagrams could be avoided with some clever caching, even though
 I am not sure how to do this in fortran.  A better alternative  is to use recursive Berends-Giele relations for color ordered amps. This is easy enough for pure gluonic amplitudes, which could be used to make tests.
 There is also another clear improvement that one could try to make, which is storing only one line of the color matrix
-and getting all the others by applying the same permutations. Finally, if one is able to generate the permutations instead of listing them in the code, one could really write a small code.
+and getting all the others by applying the same permutations. Finally, if one is able to generate the permutations instead of listing them in the code, one could really write a small code: this is certainly possible, the problem is that we need exactly the same algo in Fortran (to run the code) and in Python (to write the code and make the identification of the jamp(i) with the corresponding element in the color matrix. 
 
 === Third Step : Expand the results in powers of 1/Nc and MC over color flows ===