Ramsauer approach for light scattering on non-absorbing spherical particles and application to the Henyey-Greenstein phase function

We present a new method to study light scattering on non-absorbing spherical particles. This method is based on the Ramsauer approach, a model known in atomic an nuclear physics. Its main advantage is its intuitive understanding of the underlying physics phenomena. We show that although the approximations are numerous, the Ramsauer analytical solutions describe fairly well the scattering phase function and the total cross section. Then this model is applied to the Henyey-Greenstein parameterisation of scattering phase function to give a relation between its asymmetry parameter and the mean particle size.Comment: 25 pages, 12 figures, journal paper, accepted in Applied Optics. arXiv admin note: text overlap with arXiv:0903.297

On the hierarchy of neutrino masses

We present a model of neutrino masses combining the seesaw mechanism and strong Dirac mass hierarchy and at the same time exhibiting a significantly reduced hierarchy at the level of active neutrino masses. The heavy Majorana masses are assumed to be degenerate. The suppression of the hierarchy is due to a symmetric and unitary operator R whose role is discussed. The model gives realistic mixing and mass spectrum. The mixing of atmospheric neutrinos is attributed to the charged lepton sector whereas the mixing of solar neutrinos is due to the neutrino sector. Small U_e3 is a consequence of the model. The masses of the active neutrinos are given by $\mu_3\approx\sqrt{\Delta m_{@}^2}$ and $\mu_1/\mu_2\approx \tan^2\theta_\odot$.Comment: 12 pages; Talk presented by M. Jezabek at 'Supersymmetry and Brane Worlds,' Fifth European Meeting Planck 02, Kazimierz, Poland, May 25-29, 2002, to appear in Acta Phys. Polon.

BEC-BCS Crossover in Neutron Matter with Renormalization Group based Effective Interactions

We study pure neutron matter in the BEC-BCS crossover regime using renormalization group based low-momentum interactions within the Nozi\`eres-Schmitt-Rink framework. This is an attempt to go beyond the mean field description for low-density matter. We work in the basis of so-called Weinberg eigenvectors where the operator $G_0V$ is diagonal, which proves to be an excellent choice that allows one to use non-local interactions in a very convenient way. We study the importance of correlations as a function of density. We notice that there is a significant reduction of the BCS critical temperature at low-densities as the neutron matter approaches the unitary limit.Comment: 10 pages and 8 figures, Figs 6 and 7 now includes higher cut-offs, discussion of the cut-off dependence improved, new Summary and Outlook section and new references adde

FDI Technology Spillovers and Wages

This study distinguishes multinational firm (MNE) technology-spillover from learning effects. Whenever learning takes time, the model predicts that foreign investors deduct the economic value of learning from wages of inexperienced workers and add it to experienced ones to prevent them from moving to local competitors. Hence, the national wage bill is unaffected by the presence of MNEs. In contrast to learning, technology spillover effects occur whenever a worker with MNE experience contributes more to local firms’ than to MNEs’ productivity. In this case, experienced MNE workers are hired by indigenous firms and the host country obtains a welfare gain from the presence of MNEs. Implications of this model for the empirical findings of the MNE wage premium and the empirical FDI technology spillover literature are also discussed.FDI, foreign takeover, cross-border M&A, FDI technology spillover

Thomas-Fermi approximation to static vortex states in superfluid trapped atomic gases

We revise the Thomas-Fermi approximation for describing vortex states in Bose condensates of magnetically trapped atoms. Our approach is based on considering the hbar -> 0 limit rather than the N -> infinity limit as Thomas-Fermi approximation in close analogy with the Fermi systems. Even for relatively small numbers of trapped particles we find good agreement between Gross-Pitaevskii and Thomas-Fermi calculations for the different contributions to the total energy of the atoms in the condensate. We also discuss the application of our approach to the description of vortex states in superfluid fermionic systems in the Ginzburg-Landau regime.Comment: 11 pages, 6 figures, revtex4, substantially revised versio

A Microscopic Calculation of Photoabsorption Cross Sections on Protons and Nuclei

A recently developed model for $\rho$-meson propagation in dense hadronic matter is applied to total photoabsorption cross sections in $\gamma$-proton and $\gamma$-nucleus reactions. Within the vector dominance model the photon coupling to the virtual pion cloud of the nucleon, two-body meson-exchange currents, as well as $\gamma$-nucleon resonances are included. Whereas the $\gamma p$ reaction is determined by the low-density limit of the model, higher orders in the nuclear density are important to correctly account for the experimental spectra observed on both light and heavy nuclei over a wide range of photon energies, including the region below the pion threshold. In connection with soft dilepton spectra in high-energy heavy-ion collisions we emphasize the importance of photoabsorption to further constrain the parameters of the model.Comment: 10 pages RevTeX, 2 eps-figure