ar X iv : h ep - p h / 97 10 22 4 v 1 2 O ct 1 99 7 The Q 2 evolution of Soffer inequality
نویسندگان
چکیده
DGLAP evolution equations may be presented in a form completely analogous to the Boltzmann equation. This provides a natural proof of the positivity of the spin-dependent parton distributions, provided the initial distributions at Q0 are also positive. In addition, the evolution to Q2 < Q0 may violate positivity, providing therefore a ’time arrow’. The positivity condition is just |∆Pij(z)| ≤ Pij(z) for z < 1 for all types of partons, while the +prescription and terms containing δ(1 − z) do not affect positivity. This method allows one to complete immediately the existing proof of Soffer inequality at leading and next-to-leading order. Key-Words : Parton distributions, polarized inequality constraints Number of figures : 3 September 1997 CPT-97/P.3538 Web address: www.cpt.univ-mrs.fr
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ar X iv : h ep - p h / 97 10 22 9 v 1 2 O ct 1 99 7 SLAC - PUB - 7663 October 1997 Z ′ INVESTIGATIONS AT FUTURE LEPTON
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