AdS/QCD, Light-Front Holography, and the Nonperturbative Running Coupling

The combination of Anti-de Sitter space (AdS) methods with light-front (LF) holography provides a remarkably accurate first approximation for the spectra and wavefunctions of meson and baryon light-quark bound states. The resulting bound-state Hamiltonian equation of motion in QCD leads to relativistic light-front wave equations in terms of an invariant impact variable $\zeta$ which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. These equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-$J$ modes in anti--de Sitter (AdS) space. The eigenvalues give the hadronic spectrum, and the eigenmodes represent the probability distributions of the hadronic constituents at a given scale. A positive-sign confining dilaton background modifying AdS space gives a very good account of meson and baryon spectroscopy and form factors. The light-front holographic mapping of this model also leads to a non-perturbative effective coupling $\alpha_s^{AdS}(Q^2)$ which agrees with the effective charge defined by the Bjorken sum rule and lattice simulations. It displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale $\sim 1$ GeV. The resulting $\beta$-function appears to capture the essential characteristics of the full $\beta$-function of QCD, thus giving further support to the application of the gauge/gravity duality to the confining dynamics of strongly coupled QCD.Comment: Invited talk, presented by SJB at SCGT09, 2009 International Workshop on Strong Coupling Gauge Theories in the LHC Era, Nagoya, December 8-11, 2009, updated figur

Connecting the Hadron Mass Scale to the Fundamental Mass Scale of Quantum Chromodynamics

Establishing an explicit connection between the long distance physics of confinement and the dynamical interactions of quarks and gluons at short distances has been a long-sought goal of quantum chromodynamics. Using holographic QCD, we derive a direct analytic relation between the scale $\kappa$ which determines the masses of hadrons and the scale $\Lambda_{s}$ which controls the predictions of perturbative QCD at very short distances. The resulting prediction $\Lambda_{s}=0.341\pm0.032$ GeV in the $\overline{MS}$ scheme agrees well with the experimental average $0.339\pm0.016$ GeV. We also derive a relation between $\Lambda_{s}$ and the QCD string tension $\sigma$. This connection between the fundamental hadronic scale underlying the physics of quark confinement and the perturbative QCD scale controlling hard collisions can be carried out in any renormalization scheme.Comment: 11 pages, 4 figures. Final version published in Phys. Lett.

The sources and interpretation of Olympic Law

In this article, Mark James and Guy Osborn discuss how the relationships between the various members of the Olympic Movement are governed by the Olympic Charter and the legal framework within which an edition of the Olympic Games is organised. The legal status of the Charter and its interpretation by the Court of Arbitration for Sport are examined to identify who is subject to its terms and how challenges to its requirements can be made. Finally, by using the UK legislation that has been enacted to regulate advertising and trading at London 2012, the far-reaching and sometimes unexpected reach of Olympic Law is explored

Coefficients of different macro-microscopic mass formulae from the AME2012 atomic mass evaluation

The coefficients of different possible macro-microscopic mass formulae previously proposed have been adjusted on 2264 experimental atomic masses extracted from the AME2012 atomic mass evaluation [1] assuming N,Z⩾8 and the one standard deviation uncertainty on the mass lower than 150 keV. All the formulae include the volume and surface energies, the Coulomb energy, the diffuseness correction to the sharp radius Coulomb energy, the shell and pairing energies and take into account or not the curvature energy, different forms of the Wigner term, a free charge radius, the experimental equivalent rms charge radius or a fixed short central radius. Masses of 976 more exotic nuclei are extrapolated from the most accurate formula

Determination of the diffusion coefficient of oxygen for a cover system including a pulp and paper by-product

ABSTRACT: Among the several solutions that have been proposed to curb the problem posed by the generation of acid rock drainage (ARD), the placement of covers with capillary barrier effect (CCBE) has received particular attention. With the creation of a capillary barrier, oxygen has to migrate through a nearly saturated layer, a much slower process than in air. As a consequence, its availability is drastically reduced, reducing ARD generation. An experimental procedure was developed to obtain the diffusion coefficient of oxygen through compacted deinking residues, an organic matter-rich by-product of paper recycling. With the oxygen concentrations obtained as a function of time, it was possible to deduce the diffusion coefficients based on the best reproductions of laboratory results, using the computer code POLLUTE v.6. As expected, it was found that the diffusion coefficient—and the associated flux—is highly influenced by the degree of saturation of the sample. Beyond a threshold in the vicinity of 85 %, a one order of magnitude drop in the diffusion coefficient was observed. A comparison of the results obtained with previously published data shows that deinking residues constitute a very effective oxygen barrier material due both to its ability to maintain a high degree of saturation and to rapidly consume oxygen. Given the latter, special care was needed in defining the most appropriate equipment design, sample preparation method, and testing procedure

A simple field method to qualify the state of saturation in capillary barriers

Abstract: A simple and straightforward field method to rapidly qualify the state of saturation of moisture retaining layers (MRL) is proposed and the details of its calibration and operation, described. The technique is based on the simple fact that if gas samples cannot be taken from a stainless tube that is inserted to the desired depth within the MRL, the air filled voids at that depth are not interconnected and the material can be qualified, for all practical purposes, as saturated. In this case, the threshold degree of saturation beyond which gas flux substantially decreases (approximately 85 %), has been attained. In several sites covered with deinking by-products (DBP), an industrial residue that can be used as alternative construction material for landfills and acid-producing mine sites covers, it has been often impossible to collect gas samples below approximately 20 cm from the surface of the DBP layer. The question was thus to know if this is a reliable indicator that the threshold degree of saturation has or not been attained and that the layer is performing its role of gas barrier. In order to answer this question, a calibration was performed in the laboratory and in the field. The calibration consisted mainly on attempting to extract gas from samples compacted at different degrees of saturation. The results show that the threshold degree of saturation for DBP is attained at approximately 83 %

Environmental, geotechnical and hydraulic behaviour of a cellulose-rich by-product used as alternative cover material

Abstract: Deinking by-product (DBP), a cellulose-rich by-product produced in the early stages of the paper recycling process, has been used as alternative material for the construction of cover systems for municipal waste disposal facilities and acid-producing mine residues. Considering the high organic content of this material, covers constructed with it are susceptible to biodegradation, thus to changes in their properties with time. With the goal of identifying the biodegradation parameters that could influence the long term behaviour of DBP covers, an experimental laboratory program was developed and a series of 15 samples of DBP were monitored in biodegradation tests, for 400 days. Periods of intermittent water percolation allowed for collection of leachate. The evolution of gas and leachate production was monitored in terms of quality and quantity. According to the results obtained, the hydraulic and geomechanical properties of importance for a cover do not seem to be adversely affected by the level of biodegradation of the DBP or by mass loss

Determination of the soil water characteristic curve of highly compressible materials: Case study of pulp and paper by-product

Abstract: A technique was developed for the determination of various points of the soil-water characteristic curve (SWCC)—including the air entry value (AEV)—of compressible materials from one single test. The testing setup, which employs the axis-translation technique, is presented and the testing methodology, explained.With the proposed methodology, it is possible to determine the volume of the sample at various stages of the desaturation process, thus making it possible to determine the degree of saturation and volumetric water content for each level of suction applied. The results of some tests performed on deinking residues (DR), a fibrous and highly compressible industrial by-product used in geoenvironmental works, are presented and discussed. It is shown that if volume changes that samples undergo during desaturation are not considered, the volumetric water content and degree of saturation of the sample is underestimated at all suction values. One important consequence is that lower hydraulic conductivities are obtained from mathematical models based on the SWCC

Anaerobic biodegradation of an organic by-products leachate by interaction with different mine tailings

Abstract: Deinking by-products from paper recycling has been used as cover material on acid-producing tailings. Due to remaining cellulose, anaerobic degradation leads to the production of an organic-rich leachate, which may percolate through the tailings. This study aims at describing the influence of the tailings’ characteristics on the attenuation of organic matter in leachate and at discussing the degradation mechanisms. To this end, leachate was mixed with different types of tailings, includ ing three unoxidized tailings with varying acid generation potentials and one tailing in three states of oxidation. Regularly, selected biochemical parameters were analyzed to access the evolution of organic components. The results show that when deinking by-products leachate was placed in contact with tailings, phase and acid-base balance reactions took place in the beginning. Subsequently, oxidationreduction reactions dominated the chemistry of the system. The type, the constituents and the state of oxid ation of the mine tailings condition the mechanisms of biodegradation of organic components. Methanogenesis was predominant in the control sample (pure organic leachate) but was absent in all leachate-tailings mixes. No biodegradation was observed in the liquid phase for oxidized tailings and the organic concentration remained constant for unoxidized tailings, independently of the acid-generation potential. The biodegradation efficiency was optimal when the leachate was in contact with a mixture of oxidized and unoxidized tailings due to sulfate-reduction