Regge trajectories and quarkonium spectrum from a first principle Salpeter equation

We compute the heavy-heavy, light-light and light-heavy quarkonium spectrum starting from a first principle Salpeter equation obtained in a preceding paper. We neglect spin-orbit structures and exclude from our treatment the light pseudoscalar states which in principle would require the use of the full Bethe-Salpeter equation due to the chiral symmetry breaking problem. For the rest we find an overall good agreement with the experimental data. In particular for the light-light case we find straight Regge trajectories with the right slope and intercepts. The strong coupling constant $\alpha_s$, the string tension $\sigma$ occurring in the potential and the heavy quark masses are taken from the heavy quarkonium semirelativistic fit with only a small rearrangement. The light quark masses are set equal to baricentral value of the current quark masses as reported by the particle data group. For what concerns the light-light and the light-heavy systems the calculation is essentially parameter free.Comment: 18 pages, 3 figures, revtex.st

Slab cracking influence in the fatigue assessment of continuous composite decks

The paper analyzes the influence of the slab cracking in the fatigue assessment of continuous composite decks by considering the effects of slab casting sequences and the shrinkage components (thermal, endogenous and drying). A numerical procedure for the stress calculation accounting for the tension stiffening of the slab longitudinal rebars is presented. The long term effects of casting sequences and concrete shrinkage are analysed with a simplified procedure based on the application of the modular ratio method. With reference to a realistic continuous twin girder composite deck the fatigue verification of the longitudinal girders is carried out by considering three different casting modalities. The obtained results show the important role of the slab casting sequences in the stress range calculation and the remarkable influence of the slab cracking in the fatigue assessment

Bethe--Salpeter equation in QCD

We extend to regular QCD the derivation of a confining $q \bar{q}$ Bethe--Salpeter equation previously given for the simplest model of scalar QCD in which quarks are treated as spinless particles. We start from the same assumptions on the Wilson loop integral already adopted in the derivation of a semirelativistic heavy quark potential. We show that, by standard approximations, an effective meson squared mass operator can be obtained from our BS kernel and that, from this, by ${1\over m^2}$ expansion the corresponding Wilson loop potential can be reobtained, spin--dependent and velocity--dependent terms included. We also show that, on the contrary, neglecting spin--dependent terms, relativistic flux tube model is reproduced.Comment: 23 pages, revte

On the validity of the reduced Salpeter equation

We adapt a general method to solve both the full and reduced Salpeter equations and systematically explore the conditions under which these two equations give equivalent results in meson dynamics. The effects of constituent mass, angular momentum state, type of interaction, and the nature of confinement are all considered in an effort to clearly delineate the range of validity of the reduced Salpeter approximations. We find that for $J\not{\hspace*{-1.0mm}=}0$ the solutions are strikingly similar for all constituent masses. For zero angular momentum states the full and reduced Salpeter equations give different results for small quark mass especially with a large additive constant coordinate space potential. We also show that $\frac{1}{m}$ corrections to heavy-light energy levels can be accurately computed with the reduced equation.Comment: Latex (uses epsf macro), 24 pages of text, 12 postscript figures included. Slightly revised version, to appear in Phys. Rev.

Highly resolved WRF-BEP/BEM simulations over Barcelona urban area with LCZ

Unidad de excelencia María de Maeztu CEX2019-000940-MThis study evaluates the performance of urban schemes integrated in the Weather Research and Forecasting model (WRF) using Local Climate Zones (LCZ) as land use classification. We applied two multi-layer urban schemes: 1) Building Effect Parameterization (BEP) and 2) Building Energy Model coupled with BEP (BEP + BEM), over the Metropolitan Area of Barcelona (MAB) at 1km2 horizontal resolution for July 2016. These two simulations were compared with observations and a standard WRF simulation (BULK approach). Corine Land Cover 2012 provides background information for the entire simulation domain, while the LCZ covers MAB classifying the land cover into 10 classes according to urban morphology and thermal properties. BULK and multi-layer urban scheme experiments present a similar general error trend: overestimation of relative humidity and planetary boundary layer height and underestimation of temperature. Although BEP has the best correlation with observations, this is the scheme with the highest value of bias and RMSE for temperature and relative humidity, in particular during the night/morning. On the other hand, BEP + BEM performed with the minimum RMSE associated for temperature and relative humidity in the entire domain. BEP + BEM has shown to be more sensitive than the other schemes over locations where the land use in the model grid differs to the real one, which is a common consequent limitation of horizontal model resolution. This study also suggests that depending on the synoptic condition the scheme accuracy on determining PBLH might change considerably

Technique utilisation and efficiency in competitive Brazilian Jiu-Jitsu matches at white and blue belts

Despite its increasing popularity, little is known about Brazilian Jiu- Jitsu and what makes a successful fighter. This work aims to start answering questions about the most used and successful techniques to allow development of coaching methods towards enhancing performance at lower belt levels. One-hundred and forty tournament fights were analysed. The most common takedown was guardpull with 94% success. Significantly more single leg takedowns were attempted for blue belts (BBs), compared to white belts (WBs) (p = 0.013). However, there was no significant difference in success (p = 0.150). WBs used three main guardpasses with 93% covering knee slice, knee pin and bullfighter. A greater variety of passes were witnessed at BB with 71% coming from these three passes. The four most commonly attempted guard sweeps were scissor sweep, back take, Xguard sweep and SitUp sweep all experiencing varying levels of success: 55% for the scissor sweep, 60% back take, 63% Xguard sweep and 38% for the sit up sweep. Of all the submissions attempted 34% were for arm bar, 21% triangle, 12% cross collar choke but there were almost an inverse relationship between use and success with the least used having higher success rates, demonstrating that variety in submissions could lead to greater chances of success