Theory of W and Z boson production

Success of precision studies in W and Z boson production at the Tevatron and LHC depends on the progress in reducing theoretical uncertainties to the level of 1-2%. I review recent developments in theoretical understanding of W and Z boson production and remaining issues to be solved to meet demands of the near-future experiments.Comment: Contribution to the proceedings of the 15th Topical Conference on Hadron Collider Physics (HCP 2004, June 14-18, 2004, East Lansing, MI); 14 pages, 8 figure

Nonlinear combining of laser beams

We propose to combine multiple laser beams into a single diffraction-limited beam by the beam self-focusing (collapse) in the Kerr medium. The beams with the total power above critical are first combined in the near field and then propagated in the optical fiber/waveguide with the Kerr nonlinearity. Random fluctuations during propagation eventually trigger strong self-focusing event and produce diffraction-limited beam carrying the critical power.Comment: 5 pages, 5 figure

Solar wind protons at 1 AU: trends and bounds, constraints and correlations

The proton temperature anisotropy in the solar wind exhibits apparent bounds which are compatible with the theoretical constraints imposed by temperature-anisotropy driven kinetic instabilities. Recent statistical analyses based on conditional averaging indicate that near these theoretical constraints the solar wind protons have typically enhanced temperatures and a weaker collisionality. Here we carefully analyze the solar wind data and show that these results are a consequence of superposition of multiple correlations in the solar wind, namely, they mostly result from the correlation between the proton temperature and the solar wind velocity and from the superimposed anti-correlation between the proton temperature anisotropy and the proton parallel beta in the fast solar wind. Colder and more collisional data are distributed around temperature isotropy whereas hotter and less collisional data have a wider range of the temperature anisotropy anti-correlated with the proton parallel beta with signatures of constraints owing to the temperature-anisotropy driven instabilities. However, most of the hot and weakly collisional data, including the hottest and least collisional ones, lies far from the marginal stability regions. Consequently, we conclude that there is no clear relation between the enhanced temperatures and instability constraints and that the conditional averaging used for these analyses must be used carefully and need to be well tested.Comment: Accepted for publication in ApJ