17,480 research outputs found
On the small- behavior of the orbital angular momentum distributions in QCD
We present the numerical solution of the leading order QCD evolution equation
for the orbital angular momentum distributions of quarks and gluons and discuss
its implications for the nucleon spin sum rule. We observe that at small-,
the gluon helicity and orbital angular momentum distributions are roughly of
the same magnitude but with opposite signs, indicating a significant
cancellation between them. A similar cancellation occurs also in the quark
sector. We explain analytically the reason for this cancellation.Comment: 12 pages. v2: two figures added, version to appear in Physics Letters
Kondo correlation and spin-flip scattering in spin-dependent transport through a quantum dot coupled to ferromagnetic leads
We investigate the linear and nonlinear dc transport through an interacting
quantum dot connected to two ferromagnetic electrodes around Kondo regime with
spin-flip scattering in the dot. Using a slave-boson mean field approach for
the Anderson Hamiltonian having finite on-site Coulomb repulsion, we find that
a spin-flip scattering always depresses the Kondo correlation at arbitrary
polarization strength in both parallel and antiparallel alignment of the lead
magnetization and that it effectively reinforces the tunneling related
conductance in the antiparallel configuration. For systems deep in the Kondo
regime, the zero-bias single Kondo peak in the differential conductance is
split into two peaks by the intradot spin-flip scattering; while for systems
somewhat further from the Kondo center, the spin-flip process in the dot may
turn the zero-bias anomaly into a three-peak structure.Comment: 4 pages, 2 figure
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