Bilocal Field Approach and Semileptonic Heavy Meson Decays

In this paper we consider the bilocal field approach for $QCD$. We obtain a bilocal effective meson action with a potential kernel given in relativistic covariant form. The corresponding Schwinger--Dyson and Bethe--Salpeter equations are investigated in detail. By introducing weak interactions into the theory we study heavy meson properties as decay constants and semileptonic decay amplitudes. Thereby, the transition from the bilocal field description to the heavy quark effective theory is discussed. Considering as example the semileptonic decay of a pseudoscalar $B$--meson into a pseudoscalar $D$--meson we obtain an integral expression for the corresponding Isgur--Wise function in terms of meson wave functions.Comment: 27 pages and 2 figures (available upon request), DESY 92-07

Hydrodynamics and evaporation of a sessile drop of capillary size

Fluid dynamics video of an evaporating sessile drop of capillary size is presented. The corresponding simulation represents the description taking into account jointly time dependent hydrodynamics, vapor diffusion and thermal conduction in an evaporating sessile drop. The fluid convection in the drop is driven by Marangoni forces associated with the temperature dependence of the surface tension. For the first time the evolution of the vortex structure in the drop during an evaporation process is obtained.Comment: APS/DFD Gallery of fluid motion 201