Harnack Inequalities for Stochastic Equations Driven by L\'evy Noise

By using coupling argument and regularization approximations of the underlying subordinator, dimension-free Harnack inequalities are established for a class of stochastic equations driven by a L\'evy noise containing a subordinate Brownian motion. The Harnack inequalities are new even for linear equations driven by L\'evy noise, and the gradient estimate implied by our log-Harnack inequality considerably generalizes some recent results on gradient estimates and coupling properties derived for L\'evy processes or linear equations driven by L\'evy noise. The main results are also extended to semi-linear stochastic equations in Hilbert spaces.Comment: 15 page

Perturbations of Functional Inequalities for L\'evy Type Dirichlet Forms

Perturbations of super Poincar\'e and weak Poincar\'e inequalities for L\'evy type Dirichlet forms are studied. When the range of jumps is finite our results are natural extensions to the corresponding ones derived earlier for diffusion processes; and we show that the study for the situation with infinite range of jumps is essentially different. Some examples are presented to illustrate the optimality of our results

Energy Dependence of Direct-Quarkonium Production in pp Collisions from Fixed-Target to LHC Energies: Complete One-Loop Analysis

We compute the energy dependence of the P_T-integrated cross section of directly produced quarkonia in pp collisions at next-to-leading order (NLO), namely up to alpha_s^3, within nonrelativistic QCD (NRQCD). Our analysis is based on the idea that the P_T-integrated and the P_T-differential cross sections can be treated as two different observables. The colour-octet NRQCD parameters needed to predict the P_T-integrated yield can thus be extracted from the fits of the P_T-differential cross sections at mid and large P_T. For the first time, the total cross section is evaluated in NRQCD at full NLO accuracy using the recent NLO fits of the P_T-differential yields at RHIC, the Tevatron and the LHC. Both the normalisation and the energy dependence of the J/psi, psi' and Upsilon(1S), we obtained, are in disagreement with the data irrespective of the fit method. The same is true if one uses CEM-like colour-octet NRQCD parameters. If, on the contrary, one disregards the colour-octet contribution, the existing data in the TeV range are well described by the alpha_s^3 contribution in the colour-singlet model --which, at alpha_s^4, however shows an unphysical energy dependence. A similar observation is made for eta(c,b). This calls for a full NNLO or for a resummation of the initial-state radiation in this channel. In any case, past claims that colour-octet transitions are dominantly responsible for low-P_T quarkonium production are not supported by our results. This may impact the interpretation of quarkonium suppression in high-energy proton-nucleus and nucleus-nucleus collisions.Comment: 15 pages, 22 Figures, LaTeX uses svepjc3.clo, svglov3.clo, svjour3.cls (included