Excitations of torelon

The excitations of gluonic flux tube in a periodic lattice are examined. Monte Carlo simulations from an anisotropic lattice are presented and the comparison with effective string models is discussed.Comment: Talk at Lattice 2003; 3 pages, 4 figure

String-like behaviour of 4d SU(3) Yang-Mills flux tubes

We present here results on the fine structure of the static q\bar q potential in d=4 SU(3) Yang-Mills theory. The potential is obtained from Polyakov loop correlators having separations between 0.3 and 1.2 fermi. Measurements were carried out on lattices of spatial extents of about 4 and 5.4 fermi. The temporal extent was 5.4 fermi in both cases. The results are analyzed in terms of the force between a q\bar q pair as well as in terms of a scaled second derivative of the potential. The data is accurate enough to distinguish between different effective string models and it seems to favour the expression for ground state energy of a Nambu-Goto string.Comment: 9 pages in LaTeX with 2 figures and 2 tables in JHEP style. Replaced to match with shortened published versio

Infinite N phase transitions in continuum Wilson loop operators

We define smoothed Wilson loop operators on a four dimensional lattice and check numerically that they have a finite and nontrivial continuum limit. The continuum operators maintain their character as unitary matrices and undergo a phase transition at infinite N reflected by the eigenvalue distribution closing a gap in its spectrum when the defining smooth loop is dilated from a small size to a large one. If this large N phase transition belongs to a solvable universality class one might be able to calculate analytically the string tension in terms of the perturbative Lambda-parameter. This would be achieved by matching instanton results for small loops to the relevant large-N-universal function which, in turn, would be matched for large loops to an effective string theory. Similarities between our findings and known analytical results in two dimensional space-time indicate that the phase transitions we found only affect the eigenvalue distribution, but the traces of finite powers of the Wilson loop operators stay smooth under scaling.Comment: 31 pages, 9 figures, typos and references corrected, minor clarifications adde

Origin of molecular oxygen in Comet 67P/Churyumov-Gerasimenko

Molecular oxygen has been detected in the coma of comet 67P/Churyumov-Gerasimenko with abundances in the 1-10% range by the ROSINA-DFMS instrument on board the Rosetta spacecraft. Here we find that the radiolysis of icy grains in low-density environments such as the presolar cloud may induce the production of large amounts of molecular oxygen. We also show that molecular oxygen can be efficiently trapped in clathrates formed in the protosolar nebula, and that its incorporation as crystalline ice is highly implausible because this would imply much larger abundances of Ar and N2 than those observed in the coma. Assuming that radiolysis has been the only O2 production mechanism at work, we conclude that the formation of comet 67P/Churyumov-Gerasimenko is possible in a dense and early protosolar nebula in the framework of two extreme scenarios: (1) agglomeration from pristine amorphous icy grains/particles formed in ISM and (2) agglomeration from clathrates that formed during the disk's cooling. The former scenario is found consistent with the strong correlation between O2 and H2O observed in 67P/C-G's coma while the latter scenario requires that clathrates formed from ISM icy grains that crystallized when entering the protosolar nebula.Comment: The Astrophysical Journal Letters, in pres

The Distribution of Constituent Charm Quarks in the Hadron

Using a statistical approach in the framework of non-covariant perturbation theory the distributions for light and charmed quarks in the hadron have been derived, taking into account the mass of the charmed quark. The parameters of the model have been extracted from the comparison with NA3 data on hadroproduction of J/psi particles. A reanalysis of the EMC data on charm production in muon-nucleon scattering has been performed. It has been found in comparison with the conventional source of charmed quarks from photon-gluon fusion, that the EMC data indicate the presence of an additional contribution from deep-inelastic scattering on charmed quarks at large x. The resulting admixture of the Fock states, containing charmed quarks in the decomposition of the proton wave function is of the order of 1%. The approach presented for the excitation of the Fock states with charmed quarks can also be applied to states with beauty quarks as well as to the hadronic component of the virtual photon (resolved photon component).Comment: 23 pages, 4 PostScript figures, Latex2e. In revised version in comparison with the original one all (?) mistypings have been corrected, one more thank has been added and the comparison of the pion and the proton J/psi production is described in more detai

The Pion Structure Function in a Constituent Model

Using the recent relatively precise experimental results on the pion structure function, obtained from Drell--Yan processes, we quantitatively test an old model where the structure function of any hadron is determined by that of its constituent quarks. In this model the pion structure function can be predicted from the known nucleon structure function. We find that the data support the model, at least as a good first approximation.Comment: 9 pages, 3 figure

Elusive vector glueball

If the vector glueball exists in the mass range that theory suggests, its resonance production cross section can be seen in e+e- annihilation only if the decay width is very narrow (< a few MeV). Otherwise it willbe observed only indirectly through its mixing with psi(2S). A few tests of the glueball-psi' mixing are proposed for future charm factories.Comment: One misleading short sentence delete

Burden of cytopaenias among HIV positive pregnant women at the University College Hospital, Ibadan

Introduction: Few studies have examined cytopaenia among HIV positive pregnant women.Objectives: To assess burden of cytopaenia among HIV positive pregnant women.Methodology: This cross-sectional study of women on HAART &lt;6months, defined anemia as hematocrit &lt;33%, leucopenia as total white blood cell count &lt;3,000 cells/mm3 and thrombocytopenia as absolute platelet count &lt;100,000 cells/mm3. Univariate and bivariate analyses were performed.Results: Over 8 years, of 1,197 women, the mean age was 29.02(±5.4) years and mean gestational age 25.9(±8.1) weeks. Prevalence of anaemia was 76.8%, leucopaenia 6.9% and thrombocytopenia 4.7%. The mean haematocrit was 28.5%(±4.5); median white blood count 5,500/mm3 ; median platelet count 200,000/mm3 and median CD4 323 cells/mm3.Mean haematocrit was highest (29.7%±5.3) in women in the first trimester but lowest (28.4% ±4.6) in women in second trimester (p=0.04). Compared with earlier trimesters, women in the third trimester had higher median white blood count (5,600 cells/mm3), higher neutrophil (61.0% ±11.2) but lower lymphocytes(28.3%± 9.2) (p=0.18; 0.00, 0.00). Median absolute platelet count was highest (206,000 cells/mm3) in the first trimester but lowest (195,000 cells/mm3) in third trimester (0.04). Women with lower CD4 had higher prevalence of cytopaenias.Conclusion: Cytopaenias are not uncommon in this population especially with lower CD4

Polyakov Loop Dynamics in the Center Symmetric Phase

A study of the center symmetric phase of SU(2) Yang Mills theory is presented. Realization of the center symmetry is shown to result from non-perturbative gauge fixing. Dictated by the center symmetry, this phase exhibits already at the perturbative level confinement like properties. The analysis is performed by investigating the dynamics of the Polyakov loops. The ultralocality of these degrees of freedom implies significant changes in the vacuum structure of the theory. General properties of the confined phase and of the transition to the deconfined phase are discussed. Perturbation theory built upon the vacuum of ultralocal Polyakov loops is presented and used to calculate, via the Polyakov loop correlator, the static quark-antiquark potential.Comment: 45 pages, LaTeX, 8 figure