20,874 research outputs found

    Unidade demonstrativa do agronegócio para a agricultura familiar.

    Get PDF
    bitstream/CNPA-2009-09/14337/1/COMTEC115.pd

    Lorentz-violating nonminimal coupling contributions in mesonic hydrogen atoms and generation of photon higher-order derivative terms

    Full text link
    We have studied the contributions of Lorentz-violating CPT-odd and CPT-even nonminimal couplings to the energy spectrum of the mesonic hydrogen and the higher-order radiative corrections to the effective action of the photon sector of a Lorentz-violating version of the scalar electrodynamics. By considering the complex scalar field describes charged mesons (pion or kaon), the non-relativistic limit of the model allows to attain upper-bounds by analyzing its contribution to the mesonic hydrogen energy. By using the experimental data for the 1S1S strong correction shift and the pure QED transitions 4P→3P4P \rightarrow 3P, the best upper-bound for the CPT-odd coupling is <10−12eV−1<10^{-12}\text{eV}^{-1} and for the CPT-even one is <10−16eV−2<10^{-16}\text{eV}^{-2}. Besides, the CPT-odd radiative correction to the photon action is a dimension-5 operator which looks like a higher-order Carroll-Field-Jackiw term. The CPT-even radiative contribution to the photon effective action is a dimension-6 operator which would be a higher-order derivative version of the minimal CPT-even term of the standard model extension

    Coupling vortex dynamics with collective excitations in Bose-Einstein Condensates

    Full text link
    Here we analyze the collective excitations as well as the expansion of a trapped Bose-Einstein condensate with a vortex line at its center. To this end, we propose a variational method where the variational parameters have to be carefully chosen in order to produce reliable results. Our variational calculations agree with numerical simulations of the Gross-Pitaevskii equation. The system considered here turns out to exhibit four collective modes of which only three can be observed at a time depending of the trap anisotropy. We also demonstrate that these collective modes can be excited using well established experimental methods such as modulation of the s-wave scattering length
    • …
    corecore