39,288 research outputs found
Remittances and inequality: a dynamic migration model
We develop a model to study the effects of migration and remittances on inequality
in the origin communities. While wealth inequality is shown to be monotonically
reduced along the time-span, the short- and the long-run impacts on income
inequality may be of opposite signs, suggesting that the dynamic relationship
between migration/remittances and inequality may well be characterized by an
inverse U-shaped pattern. This is consistent with the findings of the empirical
literature, yet offers a different interpretation from the usually assumed migration
network effects. With no need to endogenize migration costs through the role of
migration networks, we generate the same result via intergenerational wealth
accumulation
Anomalous high energy dispersion in photoemission spectra from insulating cuprates
Angle resolved photoelectron spectroscopic measurements have been performed
on an insulating cuprate Ca_2CuO_2Cl_2. High resolution data taken along the
\Gamma to (pi,pi) cut show an additional dispersive feature that merges with
the known dispersion of the lowest binding energy feature, which follows the
usual strongly renormalized dispersion of ~0.35 eV. This higher energy part
reveals a dispersion that is very close to the unrenormalized band predicted by
band theory. A transfer of spectral weight from the low energy feature to the
high energy feature is observed as the \Gamma point is approached. By comparing
with theoretical calculations the high energy feature observed here
demonstrates that the incoherent portion of the spectral function has
significant structure in momentum space due to the presence of various energy
scales.Comment: 5 pages, 3 figure
Efficient fault-tolerant routing in multihop optical WDM networks
This paper addresses the problem of efficient routing in unreliable multihop optical networks supported by Wavelength Division Multiplexing (WDM). We first define a new cost model for routing in (optical) WDM networks that is more general than the existing models. Our model takes into consideration not only the cost of wavelength access and conversion but also the delay for queuing signals arriving at different input channels that share the same output channel at the same node. We then propose a set of efficient algorithms in a reliable WDM network on the new cost model for each of the three most important communication patterns - multiple point-to-point routing, multicast, and multiple multicast. Finally, we show how to obtain a set of efficient algorithms in an unreliable WDM network with up to f faulty optical channels and wavelength conversion gates. Our strategy is to first enhance the physical paths constructed by the algorithms for reliable networks to ensure success of fault-tolerant routing, and then to route among the enhanced paths to establish a set of fault-free physical routes to complete the corresponding routing request for each of the communication patterns.published_or_final_versio
Experimental study on discretely modulated continuous-variable quantum key distribution
We present a discretely modulated continuous-variable quantum key
distribution system in free space by using strong coherent states. The
amplitude noise in the laser source is suppressed to the shot-noise limit by
using a mode cleaner combined with a frequency shift technique. Also, it is
proven that the phase noise in the source has no impact on the final secret key
rate. In order to increase the encoding rate, we use broadband homodyne
detectors and the no-switching protocol. In a realistic model, we establish a
secret key rate of 46.8 kbits/s against collective attacks at an encoding rate
of 10 MHz for a 90% channel loss when the modulation variance is optimal.Comment: 7 pages,6 figure
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