Temperature Dependence of Gluon and Quark Condensates as from Linear Confinement

The gluon and quark condensates and their temperature dependence are investigated within QCD premises. The input for the former is a gauge invariant $gg$ kernel made up of the direct (D), exchange (X) and contact(C) QCD interactions in the lowest order, but with the perturbative propagator $k^{-2}$ replaced by a `non-perturbative $k^{-4}$ form obtained via two differentiations: $\mu^2 \partial_m^2 (m^2+k^2)^{-1}$, ($\mu$ a scale parameter), and then setting $m=0$, to simulate linear confinement. Similarly for the input $q{\bar q}$ kernel the gluon propagator is replaced by the above $k^{-4}$ form. With these `linear' simulations, the respective condensates are obtained by `looping' up the gluon and quark lines in the standard manner. Using Dimensional regularization (DR), the necessary integrals yield the condensates plus temperature corrections, with a common scale parameter $\mu$ for both. For gluons the exact result is $$= {36\mu^4}\pi^{-3}\alpha_s(\mu^2)[2-\gamma - 4\pi^2 T^2/(3\mu^2)]$$. Evaluation of the quark condensate is preceded by an approximate solution of the SDE for the mass function $m(p)$, giving a recursive formula, with convergence achieved at the third iteration. Setting the scale parameter $\mu$ equal to the universal Regge slope $1 GeV^2$, the gluon and quark condensates at T=0 are found to be $0.586 Gev^4$ and $(240-260 MeV)^3$ respectively, in fair accord with QCD sum rule values. Next, the temperature corrections (of order $-T^2$ for both condensates) is determined via finite-temperature field theory a la Matsubara. Keywords: Gluon Condensate, mass tensor, gauge invariance, linear confinement, finite-temperature, contour-closing. PACS: 11.15.Tk ; 12.38.Lg ; 13.20.CzComment: 13 pages (LaTeX) including 2 figure

Coherent structures in fully-developed pipe turbulence

A turbulent mean profile for pipe flow is prescribed which closely matches experimental observations. The nature of perturbations superimposed upon this profile is then considered. Optimal growth calculations predict two distinct classes of structures, clearly associated with near-wall and large-scale structures. Quantitative correspondence of the spanwise wavelength of wall-structures with experimental observations is very good. The response to harmonic forcing is also considered, and the linear growth tested with direct numerical simulation of forced turbulence. Despite the very simple eddy viscosity assumption, this linear approach predicts well the surprisingly large growth of outer-scale modes in the bulk flow. Un profil moyen turbulent est prescrit dans une conduite cylindrique, en adequation avec les observations experimentales. Nous considerons ensuite la nature des perturbations a cet ecoulement synthetique. Le calcul des croissances optimales predit deux types de structures, associees respectivement aux structures de proche-paroi et de grande echelle. Un excellent accord quantitatif est trouve avec les resultats experimentaux quant a la longueur d'onde transversale. La reponse harmonique est egalement etudiee, et la croissance lineaire observee comparee a des simulations numeriques directes de turbulence forcee. Malgre de l'hypothese simple de type `Eddy viscosity', cette approche lineaire predit efficacement la croissance spectaculaire des modes de grande echelle au coeur de l'ecoulement.Comment: 5 pages; Congres Francais de Mecanique, Marseille (2009

Relativistic Hydrodynamic Cosmological Perturbations

Relativistic cosmological perturbation analyses can be made based on several different fundamental gauge conditions. In the pressureless limit the variables in certain gauge conditions show the correct Newtonian behaviors. Considering the general curvature ($K$) and the cosmological constant ($\Lambda$) in the background medium, the perturbed density in the comoving gauge, and the perturbed velocity and the perturbed potential in the zero-shear gauge show the same behavior as the Newtonian ones in general scales. In the first part, we elaborate these Newtonian correspondences. In the second part, using the identified gauge-invariant variables with correct Newtonian correspondences, we present the relativistic results with general pressures in the background and perturbation. We present the general super-sound-horizon scale solutions of the above mentioned variables valid for general $K$, $\Lambda$, and generally evolving equation of state. We show that, for vanishing $K$, the super-sound-horizon scale evolution is characterised by a conserved variable which is the perturbed three-space curvature in the comoving gauge. We also present equations for the multi-component hydrodynamic situation and for the rotation and gravitational wave.Comment: 16 pages, no figure, To appear in Gen. Rel. Gra

Lines on projective varieties and applications

The first part of this note contains a review of basic properties of the variety of lines contained in an embedded projective variety and passing through a general point. In particular we provide a detailed proof that for varieties defined by quadratic equations the base locus of the projective second fundamental form at a general point coincides, as a scheme, with the variety of lines. The second part concerns the problem of extending embedded projective manifolds, using the geometry of the variety of lines. Some applications to the case of homogeneous manifolds are included.Comment: 15 pages. One example removed; one remark and some references added; typos correcte

Field evaluation of the CATT/Trypanosoma brucei gambiense on blood-impregnated filter papers for diagnosis of human African trypanosomiasis in southern Sudan.

Most Human African Trypanosomiasis (HAT) control programmes in areas endemic for Trypanosoma brucei gambiense rely on a strategy of active mass screening with the Card Agglutination Test for Trypanosomiasis (CATT)/T. b. gambiense. We evaluated the performance, stability and reproducibility of the CATT/T. b. gambiense on blood-impregnated filter papers (CATT-FP) in Kajo-Keji County, South-Sudan, where some areas are inaccessible to mobile teams. The CATT-FP was performed with a group of 100 people with a positive CATT on whole blood including 17 confirmed HAT patients and the results were compared with the CATT on plasma (CATT-P). The CATT-FP was repeated on impregnated filter papers stored at ambient and refrigerated temperature for 1, 3, 7 and 14 days. Another 82 patients with HAT, including 78 with a positive parasitology, were tested with the CATT-FP and duplicate filter paper samples were sent to a reference laboratory to assess reproducibility. The CATT-FP was positive in 90 of 99 patients with HAT (sensitivity: 91%). It was less sensitive than the CATT-P (mean dilution difference: -2.5). There was no significant loss of sensitivity after storage for up to 14 days both at ambient and cool temperature. Reproducibility of the CATT-FP was found to be excellent (kappa: 0.84). The CATT-FP can therefore be recommended as a screening test for HAT in areas where the use of CATT-P is not possible. Further studies on larger population samples in different endemic foci are still needed before the CATT-FP can be recommended for universal use

An optical NMR spectrometer for Larmor-beat detection and high-resolution POWER NMR

Optical nuclear magnetic resonance (ONMR) is a powerful probe of electronic properties in III-V semiconductors. Larmor-beat detection (LBD) is a sensitivity optimized, time-domain NMR version of optical detection based on the Hanle effect. Combining LBD ONMR with the line-narrowing method of POWER (perturbations observed with enhanced resolution) NMR further enables atomically detailed views of local electronic features in III-Vs. POWER NMR spectra display the distribution of resonance shifts or line splittings introduced by a perturbation, such as optical excitation or application of an electric field, that is synchronized with a NMR multiple-pulse time-suspension sequence. Meanwhile, ONMR provides the requisite sensitivity and spatial selectivity to isolate local signals within macroscopic samples. Optical NMR, LBD, and the POWER method each introduce unique demands on instrumentation. Here, we detail the design and implementation of our system, including cryogenic, optical, and radio-frequency components. The result is a flexible, low-cost system with important applications in semiconductor electronics and spin physics. We also demonstrate the performance of our systems with high-resolution ONMR spectra of an epitaxial AlGaAs/GaAs heterojunction. NMR linewidths down to 4.1 Hz full width at half maximum were obtained, a 10^3-fold resolution enhancement relative any previous optically detected NMR experiment

Percolation of Immobile Domains in Supercooled Thin Polymeric Films

We present an analysis of heterogeneous dynamics in molecular dynamics simulations of a thin polymeric film, supported by an absorbing structured surface. Near the glass transition "immobile" domains occur throughout the film, yet the probability of their occurrence decreasing with larger distance from the surface. Still, enough immobile domains are located near the free surface to cause them to percolate in the direction perpendicular to surface, at a temperature near the glass transition temperature. This result is in agreement with a recent theoretical model of glass transition