A slip model for micro/nano gas flows induced by body forces

A slip model for gas flows in micro/nano-channels induced by external body forces is derived based on Maxwell's collision theory between gas molecules and the wall. The model modifies the relationship between slip velocity and velocity gradient at the walls by introducing a new parameter in addition to the classic Tangential Momentum Accommodation Coefficient. Three-dimensional Molecular Dynamics simulations of helium gas flows under uniform body force field between copper flat walls with different channel height are used to validate the model and to determine this new parameter

Improved Smoothing Algorithms for Lattice Gauge Theory

The relative smoothing rates of various gauge field smoothing algorithms are investigated on ${\cal O}(a^2)$-improved \suthree Yang--Mills gauge field configurations. In particular, an ${\cal O}(a^2)$-improved version of APE smearing is motivated by considerations of smeared link projection and cooling. The extent to which the established benefits of improved cooling carry over to improved smearing is critically examined. We consider representative gauge field configurations generated with an ${\cal O}(a^2)$-improved gauge field action on \1 lattices at $\beta=4.38$ and \2 lattices at $\beta=5.00$ having lattice spacings of 0.165(2) fm and 0.077(1) fm respectively. While the merits of improved algorithms are clearly displayed for the coarse lattice spacing, the fine lattice results put the various algorithms on a more equal footing and allow a quantitative calibration of the smoothing rates for the various algorithms. We find the relative rate of variation in the action may be succinctly described in terms of simple calibration formulae which accurately describe the relative smoothness of the gauge field configurations at a microscopic level

Scaling Behavior of the Landau Gauge Overlap Quark Propagator

The properties of the momentum space quark propagator in Landau gauge are examined for the overlap quark action in quenched lattice QCD. Numerical calculations are done on three lattices with different lattice spacings and similar physical volumes to explore the approach of the quark propagator towards the continuum limit. We have calculated the nonperturbative momentum-dependent wavefunction renormalization function $Z(p^2)$ and the nonperturbative mass function $M(p^2)$ for a variety of bare quark masses and extrapolate to the chiral limit. We find the behavior of $Z(p^2)$ and $M(p^2)$ are in good agreement for the two finer lattices in the chiral limit. The quark condensate is also calculated.Comment: 3 pages, Lattice2003(Chiral fermions

Estimations for the Single Diffractive production of the Higgs boson at the Tevatron and the LHC

The single diffractive production of the standard model Higgs boson is computed using the diffractive factorization formalism, taking into account a parametrization for the Pomeron structure function provided by the H1 Collaboration. We compute the cross sections at next-to-leading order accuracy for the gluon fusion process, which includes QCD and electroweak corrections. The gap survival probability ($$) is also introduced to account for the rescattering corrections due to spectator particles present in the interaction, and to this end we compare two different models for the survival factor. The diffractive ratios are predicted for proton-proton collisions at the Tevatron and the LHC for the Higgs boson mass of $M_H$ = 120 GeV. Therefore, our results provide updated estimations for the diffractive ratios of the single diffractive production of the Higgs boson in the Tevatron and LHC kinematical regimes.Comment: 20 pages, 6 figures, 3 table

Quark propagator in a covariant gauge

Using mean--field improved gauge field configurations, we compare the results obtained for the quark propagator from Wilson fermions and Overlap fermions on a \3 lattice at a spacing of $a=0.125(2)$ fm.Comment: 5 pages, 8 figures, talk given by F.D.R. Bonnet at LHP 2001 workshop, Cairns, Australi

Infinite Volume and Continuum Limits of the Landau-Gauge Gluon Propagator

We extend a previous improved action study of the Landau gauge gluon propagator, by using a variety of lattices with spacings from $a = 0.17$ to 0.41 fm, to more fully explore finite volume and discretization effects. We also extend a previously used technique for minimizing lattice artifacts, the appropriate choice of momentum variable or ``kinematic correction'', by considering it more generally as a ``tree-level correction''. We demonstrate that by using tree-level correction, determined by the tree-level behavior of the action being considered, it is possible to obtain scaling behavior over a very wide range of momenta and lattice spacings. This makes it possible to explore the infinite volume and continuum limits of the Landau-gauge gluon propagator.Comment: 24 pages RevTex, 18 figures; Responses to referee comments, minor change

Evolution of the decay mechanisms in central collisions of XeXe + SnSn from E/AE/A = 8 to 29 MeVMeV

Collisions of Xe+Sn at beam energies of $E/A$ = 8 to 29 $MeV$ and leading to fusion-like heavy residues are studied using the $4\pi$ INDRA multidetector. The fusion cross section was measured and shows a maximum at $E/A$ = 18-20 $MeV$. A decomposition into four exit-channels consisting of the number of heavy fragments produced in central collisions has been made. Their relative yields are measured as a function of the incident beam energy. The energy spectra of light charged particles (LCP) in coincidence with the fragments of each exit-channel have been analyzed. They reveal that a composite system is formed, it is highly excited and first decays by emitting light particles and then may breakup into 2- or many- fragments or survives as an evaporative residue. A quantitative estimation of this primary emission is given and compared to the secondary decay of the fragments. These analyses indicate that most of the evaporative LCP precede not only fission but also breakup into several fragments.Comment: Invited Talk given at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS

Seasonal dynamics and mortality rates of Calanus helgolandicus over two years at a station in the English Channel

The stage-specific abundance and egg production rates of Calanus helgolandicus were determined on a near-weekly basis over 2 yr at a 50 m deep station in the SW English Channel (Stn L4). Mortality rates were derived using a vertical life-table approach across eggs, nauplii and also the CV–adult stage pair. The results demonstrate strong seasonal patterns in the mortality rates of egg and nauplii and the CV–adult stage pair, but with different relative rates and somewhat different seasonalities. Mortality was highest in the egg and egg–NI stages, averaging 6.1 and ~1.5 d–1, respectively, with the percentage surviving through the egg–NI stage pair often <<10%. Although the instantaneous removal rate of eggs was significantly related to adult abundance (p < 0.001, r2 = 0.221), densities of adult C. helgolandicus seemed too low to account for these rates. Examination of the relationship between CV–adult female mortality and the abundance of the dominant invertebrate predators revealed statistically significant relationships (p < 0.001 r2 = 0.276 for chaetognaths; p < 0.001 r2 = 0.125 for siphonophores); however, the variability explained by temperature was much higher (p < 0.001 r2 = 0.652). The egg–NI and NI–NII stage pairs also showed a highly statistically significant positive relationship between mortality and temperature. For the first time we compared mortality rates for egg–NI using 2 vertical methods—one using measurements of egg and NI abundance (Method A) the other using egg production rates and NI abundance (Method B)—and found the two to be similar, although Method B gave higher values. Finally, as many mortality equations do not consider the bias resulting from the presence of eggs incapable of hatching in the field, we derived and applied new equations for mortality of eggs and egg–NI (Method A) that incorporated egg hatching success. At low hatching success or low mortality rates, this correction can alter estimates of mortality rates significantly

The FLIC Overlap Quark Propagator

FLIC overlap fermions are a variant of the standard (Wilson) overlap action, with the FLIC (Fat Link Irrelevant Clover) action as the overlap kernel rather than the Wilson action. The structure of the FLIC overlap fermion propagator in momentum space is studied, and a comparison against previous studies of the Wilson overlap propagator in quenched QCD is performed. To explore the scaling properties of the propagator for the two actions, numerical calculations are performed in Landau Gauge across three lattices with different lattice spacing $a$ and similar physical volumes. We find that at light quark masses the acti ons agree in both the infrared and the ultraviolet, but at heavier masses some disagreement in the ultraviolet appears. This is attributed to the two action s having different discretisation errors with the FLIC overlap providing superior performance in this regime. Both actions scale reasonably, but some scaling violations are observed

Nonperturbative improvement and tree-level correction of the quark propagator

We extend an earlier study of the Landau gauge quark propagator in quenched QCD where we used two forms of the O(a)-improved propagator with the Sheikholeslami-Wohlert quark action. In the present study we use the nonperturbative value for the clover coefficient c_sw and mean-field improvement coefficients in our improved quark propagators. We compare this to our earlier results which used the mean-field c_sw and tree-level improvement coefficients for the propagator. We also compare three different implementations of tree-level correction: additive, multiplicative, and hybrid. We show that the hybrid approach is the most robust and reliable and can successfully deal even with strong ultraviolet behavior and zero-crossing of the lattice tree-level expression. We find good agreement between our improved quark propagators when using the appropriate nonperturbative improvement coefficients and hybrid tree-level correction. We also present a simple extrapolation of the quark mass function to the chiral limit.Comment: 12 pages, 18 figures, RevTeX4. Some clarifications and corrections. Final version, to appear in Phys.Rev.