It has been observed that in the DIS scheme the refactorization of the DrellYan cross section leading to exponentiation of threshold logarithms can also be used to organize a class of constant terms, most of which arise from the ratio of the timelike Sudakov form factor to its spacelike counterpart. We extend this exponentiation to include all constant terms, and demonstrate how a similar organization may be achieved in the MS scheme. We study the relevance of these exponentiations in a two-loop analysis.

Abstract. Four empirically equivalent versions of general relativity, namely standard GR, Lorentz-invariant gravitational theory, and the gravitational gauge theories of the Lorentz and translation groups, are investigated in the form of a case study for theory underdetermination. The various ontological indeterminacies (both underdetermination and inscrutability of reference) inherent in gravitational theories are analyzed in a detailed comparative study. The concept of practical underdetermination is proposed, followed by a discussion of its adequacy to describe scientific progress.

We present the threshold resummation for the cross section of heavy quark production in polarized deep-inelastic scattering to next-to-leading logarithmic accuracy and in singleparticle inclusive kinematics. We expand our resummed result in α s to next-to-leading and next-to-next-to-leading order and study the impact of these higher order corrections on the charm structure function g c 1 in the kinematical range accessible to the HERMES and COMPASS experiments. a teynck@nikhef.nl b t66@nikhef.nl

We compare the phase space slicing and dipole subtraction methods in the computation of the inclusive and differential next-to-leading order cross sections for heavy quark production in the simple process γ * → QQ. For the phase space slicing method we study the effects of improvement terms that remove restrictions on the slicing parameter s min . For the dipole method our comparison is a first check on some of its counterterms involving massive quarks, derived recently. In our comparison we address issues such as numerical accuracy and efficiency.

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