143,562 research outputs found
Optically induced spin polarization of an electric current through a quantum dot
We examine electron transport through semiconductor quantum dot subject to a
continuous circularly polarized optical irradiation resonant to the electron -
heavy hole transition. Electrons having certain spin polarization experience
Rabi oscillation and their energy levels are shifted by the Rabi frequency.
Correspondingly, the equilibrium chemical potential of the leads and the
lead-to-lead bias voltage can be adjusted so only electrons with spin-up
polarization or only electrons with spin-down polarization contribute to the
current. The temperature dependence of the spin polarization of the current is
also discussed.Comment: Several misprints are correcte
Kinetic equations for ultrarelativistic particles in a Robertson-Walker Universe and isotropization of relict radiation by gravitational interactions
Kinetic equations for ultrarelativistic particles with due account of
gravitational interactions with massive particles in the Robertson-Walker
universe are obtained. On the basis of an exact solution of the kinetic
equations thus obtained, a conclusion is made as to the high degree of the
uniformity of the relict radiation on scales with are less than .Comment: 19 pages, 2 figures, 13 reference
QCD analysis of near-to-planar 3-jet events
Perturbative QCD analysis is presented of the cumulative out-of-plane
momentum distribution in the near-to-planar e+e- annihilation events, K_out <<
Q. In this kinematical region multiple gluon radiation effects become
essential. They are resummed with the single-logarithmic accuracy, which
programme includes the 2-loop treatment of the basic radiation and matching
with the exact O(alpha_s^2) result.
Dedicated experimental analyses of 3-jet event characteristics are of special
interest for the study of the non-perturbative confinement effects.Comment: 32 pages, 1 figure, JHEP class include
QCD analysis of D-parameter in near-to-planar three-jet events
We present the QCD analysis of D-parameter distribution in near-to-planar
3-jet e+e- annihilation events. We derive the all-order resummed perturbative
prediction and the leading power suppressed non-perturbative corrections both
to the mean value and the distribution. Here non-perturbative corrections are
larger than in 2-jet shape observables, so that higher order non-perturbative
effects could be relevant. Experimental data (not yet available) are needed in
order to cast light on this important point. The technique we develop aims at
improving the accuracy of the theoretical description of multi-jet ensembles,
in particular in hadron-hadron collisions.Comment: 26 pages, 6 figures, JHEP class include
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