At Thu, 15 Apr 2010 15:11:24 -0400, Hergert, Heiko wrote: > I just came about this bug in gsl_sf_coupling_6j() in GSL 1.13 (haven't > checked newer builds). > > The check of the triangle conditions (via the routine > triangle_selection_fails) doesn't properly rule out all unphysical > combinations of angular momenta. For instance > > gsl_sf_coupling(0, 2, 2, 44, 43, 43) = 0.087039 > > but the routine should return 0 since this symbol is unphysical: > jb=1 and jc=21 cannot be coupled to jf=43/2=21.5 although the triangle > tests are nominally satisfied > > abs(1-21.5)=20.5 <= 21 <= 22.5. > > A possible fix would be to check if > > (two_ja + two_jb + two_jc)%2 == 0 > > ja+jb+jc is always integer in physically allowed couplings (i.e., > 2*(ja+jb+jc) must be even). > > The routine for the 3j symbol is not similarly affected due to the > additional m_selection_fails() test.
Thanks for the bug report, I've logged it in the bug tracker at https://savannah.gnu.org/bugs/index.php?2960 -- Brian Gough GNU Scientific Library - http://www.gnu.org/software/gsl/ _______________________________________________ Bug-gsl mailing list [email protected] http://lists.gnu.org/mailman/listinfo/bug-gsl
