Polarization of B -> VV: experimental status

The experimental status of the polarization measurements in B to charmless vector-vector decays by both the Belle and Babar experiments is reviewed. The results obtained in related vector-tensor, axial vector-vector, and axial vector-axial vector modes are also given.Comment: 6 pages, 5 figures, Proceedings of CKM2010, the 6th International Workshop on the CKM Unitarity Triangle, University of Warwick, UK, 6-10 September 201

Regularity criterion for 3D Navier-Stokes equations in terms of the direction of the velocity

In this short note, we give a link between the regularity of the solution $u$ to the 3D Navier-Stokes equation, and the behavior of the direction of the velocity $u/|u|$. It is shown that the control of \Div (u/|u|) in a suitable $L_t^p(L_x^q)$ norm is enough to ensure global regularity. The result is reminiscent of the criterion in terms of the direction of the vorticity, introduced first by Constantin and Fefferman. But in this case the condition is not on the vorticity, but on the velocity itself. The proof, based on very standard methods, relies on a straightforward relation between the divergence of the direction of the velocity and the growth of energy along streamlines.Comment: 6 page

Cell Adhesion: A surprising cohesive force

When an experimentalist or a biological mechanism applies an external force onto a cell chemically sticking to its substrate, a reacting "suction" force, due to the slow penetration of the surrounding fluid between the cell and the substrate, opposes to the dissociation. This force can overcome other known adhesive forces when the process is sufficiently violent (typically 10^5^ pN). Its maximal contribution to the total adhesive energy of the cell can then be estimated to 2 10^-3^ J/m2. The physical origin of this effect is quite simple, and it may be compared with that leaning a "suction-cup" against a bathroom wall. We address the consequences of this effect on (i) the separation energy, (ii) the motion of the fluid surrounding the cell, more especially, on the pumping of the fluid by moving cells, and (iii) the inhibition of cell motion

Delocalization due to correlations in two-dimensional disordered systems

We study the spectral statistics of interacting spinless fermions in a two-dimensional disordered lattice. Within a full quantum treatment for small few-particle-systems, we compute the low-energy many-body states numerically. While at weak disorder the interactions reduce spectral correlations and lead to localization, for the case of strong disorder we find that a moderate Coulomb interaction has a delocalizing effect. In addition, we observe a non-universal structure in the level-spacing distribution which we attribute to a mechanism reinforcing spectral correlations taking place in small systems at strong disorder.Comment: 6 pages, 4 figures, corrected typo