Dispersive approach in Sudakov resummation

The dispersive approach to power corrections is given a precise implementation, valid beyond single gluon exchange, in the framework of Sudakov resummation for deep inelastic scattering and the Drell-Yan process. It is shown that the assumption of infrared finite Sudakov effective couplings implies the universality of the corresponding infrared fixed points. This property is closely tied to the universality of the virtual contributions to space-like and time-like processes, encapsulated in the second logarithmic derivative of the quark form factor.Comment: 3 pages, talk given at Quark Confinement and the Hadron Spectrum 7, Ponta Delgada, Azores, Portugal, 2-7 Sep 2006, LaTeX, uses aip-6s.clo, aipproc.cls and aipxfm.sty (included

Conformal window and Landau singularities

A physical characterization of Landau singularities is emphasized, which should trace the lower boundary N_f^* of the conformal window in QCD and supersymmetric QCD. A natural way to disentangle ``perturbative'' from ``non-perturbative'' contributions below N_f^* is suggested. Assuming an infrared fixed point is present in the perturbative part of the QCD coupling even in some range below N_f^* leads to the condition gamma(N_f^*)=1, where gamma is the critical exponent. This result is incompatible with the existence of an analogue of Seiberg free dual magnetic phase in QCD. Using the Banks-Zaks expansion, one gets 4<N_f^*<6. The low value of N_f^* gives some justification to the infrared finite coupling approach to power corrections, and suggests a way to compute their normalization from perturbative input. If the perturbative series are still asymptotic in the negative coupling region, the presence of a negative ultraviolet fixed point is required both in QCD and in supersymmetric QCD to preserve causality within the conformal window. Some evidence for such a fixed point in QCD is provided through a modified Banks-Zaks expansion. Conformal window amplitudes, which contain power contributions, are shown to remain generically finite in the N_f=-\infty one-loop limit in simple models with infrared finite perturbative coupling.Comment: 35 pages, 1 figure, JHEP style. A new section added to point out the results give some justification to the infrared finite coupling approach to power corrections, and suggest a way to compute their normalization from perturbative inpu

From stars to nuclei

We recall the basic physical principles governing the evolution of stars with some emphasis on the role played by the nuclear reactions. We argue that in general it is not possible from observations of stars to deduce constraints on the nuclear reaction rates. This is the reason why precise measurements of nuclear reaction rates are a necessity in order to make progresses in stellar physics, nucleosynthesis and chemical evolution of galaxies. There are however some stars which provides useful constraint on nuclear processes. The Wolf-Rayet stars of the WN type present at their surface CNO equilibrium patterns. There is also the particular case of the abundance of $^{22}$Ne at the surface of WC stars. The abundance of this element is a measure of the initial CNO content. Very interestingly, recent determinations of its abundance at the surface of WC stars tend to confirm that massive stars in the solar neighborhood have initial metallicities in agreement with the Asplund et al. (2005) solar abundances.Comment: 8 pages, 2 figures, be published in "European Physical Journal: Special Topics

In search of foreign influences, other than French, in nineteenth-century Belgian court decisions

In many senses, nineteenth-century Belgium can be considered to be a 'legal province' of Belgium. In the tradition of the exegetical school, legislation is the one and only formal source of law for judicial decisions. This legislation is primarily composed of the Napoleonic codes. Judges seem to be afraid of referring to other sources. If a ‘foreign’ source is quoted, it is a French one

Polarization of B -> VV: experimental status

The experimental status of the polarization measurements in B to charmless vector-vector decays by both the Belle and Babar experiments is reviewed. The results obtained in related vector-tensor, axial vector-vector, and axial vector-axial vector modes are also given.Comment: 6 pages, 5 figures, Proceedings of CKM2010, the 6th International Workshop on the CKM Unitarity Triangle, University of Warwick, UK, 6-10 September 201

Soils and paleosoils of the Galapagos Islands : what we know and what we don't know, a meta-analysis

Accessible information on Galapagos soils is very limited. Much of the existing, although still scarce, information is several decades old and not easily retrieved. The aim of this paper is to present a critical synthesis. Three local soil-forming factors (parent material, climate, and vegetation) are briefly highlighted, followed by a more detailed discussion of the hypsometric soil sequence on Santa Cruz, the only island where systematic information was recorded by a Belgian geopedological mission in 1962. Five zones are distinguished from the coast toward the top of the island: a dry coastal area, containing superficial and interstitial reddish, smectite-bearing soils between basalt blocks; a transition zone of brown, also smectite-bearing soils; and three subsequent higher zones covered by deeper, brown soils with probably andosolic characteristics. Trace element analyses point to a uniform composition of the parent material and a more progressed weathering on the higher slopes. Micromorphological characteristics of the soils are discussed. Soils of Santa Fe are comparable with those of the coastal zone of Santa Cruz but show higher amounts of P and S, probably of avian origin. Deeper, reddish clayey soils cover San Cristobal and are at least partly pre-Holocene. On the younger islands, no soils seem to be present

Stickelberger's congruences for absolute norms of relative discriminants

We give an improvement of a result of J. Martinet on Stickelberger's congruences for the absolute norms of relative discriminants of number fields, by using classical arguments of class field theory