44,404 research outputs found
Revisit the spin-FET: Multiple reflections, inelastic scattering, and lateral size effects
We revisit the spin-injected field effect transistor (spin-FET) by simulating
a lattice model based on recursive lattice Green's function approach. In the
one-dimensional case and coherent regime, the simulated results reveal
noticeable differences from the celebrated Datta-Das model, which motivate thus
an improved treatment and lead to analytic and generalized result. The
simulation also allows us to address inelastic scattering (using B\"uttiker's
fictitious reservoir approach) and lateral confinement effects on the control
of spins which are important issues in the spin-FET device.Comment: 9 pages, 4 figure
Transplanckian Dispersion Relation and Entanglement Entropy of Blackhole
The quantum correction to the entanglement entropy of the event horizon is
plagued by the UV divergence due to the infinitely blue-shifted near horizon
modes. The resolution of this UV divergence provides an excellent window to a
better understanding and control of the quantum gravity effects. We claim that
the key to resolve this UV puzzle is the transplanckian dispersion relation. We
calculate the entanglement entropy using a very general type of transplanckian
dispersion relation such that high energy modes above a certain scale are
cutoff, and show that the entropy is rendered UV finite. We argue that modified
dispersion relation is a generic feature of string theory, and this boundedness
nature of the dispersion relation is a general consequence of the existence of
a minimal distance in string theory.Comment: 7 pages. To appear in the proceedings of 36th International Symposium
Ahrenshoop on the theory of Elementary Particles: Recent Developments in
String/M Theory and Field Theory, Berlin, Germany, 26-30 Aug 200
Study of the weak annihilation contributions in charmless decays
In this paper, in order to probe the spectator-scattering and weak
annihilation contributions in charmless (where stands for a
light vector meson) decays, we perform the -analyses for the end-point
parameters within the QCD factorization framework, under the constraints from
the measured , , and
decays. The fitted results indicate that the end-point
parameters in the factorizable and nonfactorizable annihilation topologies are
non-universal, which is also favored by the charmless and (where
stands for a light pseudo-scalar meson) decays observed in the previous
work. Moreover, the abnormal polarization fractions measured by the LHCb
collaboration can be reconciled through the weak annihilation corrections.
However, the branching ratio of decay exhibits a
tension between the data and theoretical result, which dominates the
contributions to in the fits. Using the fitted end-point
parameters, we update the theoretical results for the charmless
decays, which will be further tested by the LHCb and Belle-II experiments in
the near future.Comment: 31 pages, 4 figures, 6 table
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