635 research outputs found
Changing Patterns of Income Inequality in U.S. Counties, 1970–2000
The upswing in economic inequality that has affected a number of advanced industrial societies in the late 20th century has been particularly conspicuous in the United States. The authors explore its causes using data on the distribution of family income in 3,098 U.S. counties in 1970, 1980, 1990, and 2000. The authors build a model of within-county income inequality that assumes that distribution processes involving labor market and sociodemographic variables operate primarily at the county level and those involving the political and institutional context operate primarily at the state level. Multilevel methods are used to distinguish county cross-sectional, state cross-sectional, and longitudinal effects on inequality. The authors find that, when features of the state-level institutional and political context are associated with inequality, these effects are larger longitudinally than cross-sectionally. A range of other factors, including economic development, labor force changes, shifts in the racial/ethnic and gender composition of the labor force, educational expansion, and urbanization are found to have comparatively large effects, both longitudinally and cross-sectionally
Quantum network coding for quantum repeaters
This paper considers quantum network coding, which is a recent technique that
enables quantum information to be sent on complex networks at higher rates than
by using straightforward routing strategies. Kobayashi et al. have recently
showed the potential of this technique by demonstrating how any classical
network coding protocol gives rise to a quantum network coding protocol. They
nevertheless primarily focused on an abstract model, in which quantum resource
such as quantum registers can be freely introduced at each node. In this work,
we present a protocol for quantum network coding under weaker (and more
practical) assumptions: our new protocol works even for quantum networks where
adjacent nodes initially share one EPR-pair but cannot add any quantum
registers or send any quantum information. A typically example of networks
satisfying this assumption is {\emph{quantum repeater networks}}, which are
promising candidates for the implementation of large scale quantum networks.
Our results thus show, for the first time, that quantum network coding
techniques can increase the transmission rate in such quantum networks as well.Comment: 9 pages, 11figure
Globalization and the Great U-Turn: Income Inequality Trends in 16 OECD Countries
The debate on the resurgence of income inequality in some advanced industrial societies has often focused on the impact of an increasingly integrated world economy, typified by growing capital mobility, heightened international competition, and an increase in migration. This study represents one of the first systematic, cross-national examinations of the role of globalization in the inequality "U-turn." Results indicate, on the one hand, that total inequality variation is principally affected by the percentage of the labor force in agriculture, followed by the institutional factors union density and decom-modification, and only then by globalization. On the other hand, longitudinal variation in inequality, while still dominated by the percentage of the labor force in agriculture, is also principally affected by aspects of globalization, such as southern import penetration and direct investment outflow, and to a lesser extent by migration. In other words, globalization explains the longitudinal trend of increasing inequality that took place within many industrial countries better than it does cross-sectional inequality differences among countries
Exponential Separation of Quantum and Classical Online Space Complexity
Although quantum algorithms realizing an exponential time speed-up over the
best known classical algorithms exist, no quantum algorithm is known performing
computation using less space resources than classical algorithms. In this
paper, we study, for the first time explicitly, space-bounded quantum
algorithms for computational problems where the input is given not as a whole,
but bit by bit. We show that there exist such problems that a quantum computer
can solve using exponentially less work space than a classical computer. More
precisely, we introduce a very natural and simple model of a space-bounded
quantum online machine and prove an exponential separation of classical and
quantum online space complexity, in the bounded-error setting and for a total
language. The language we consider is inspired by a communication problem (the
set intersection function) that Buhrman, Cleve and Wigderson used to show an
almost quadratic separation of quantum and classical bounded-error
communication complexity. We prove that, in the framework of online space
complexity, the separation becomes exponential.Comment: 13 pages. v3: minor change
Experimental violation of a Bell's inequality in time with weak measurement
The violation of J. Bell's inequality with two entangled and spatially
separated quantum two- level systems (TLS) is often considered as the most
prominent demonstration that nature does not obey ?local realism?. Under
different but related assumptions of "macrorealism", plausible for macroscopic
systems, Leggett and Garg derived a similar inequality for a single degree of
freedom undergoing coherent oscillations and being measured at successive
times. Such a "Bell's inequality in time", which should be violated by a
quantum TLS, is tested here. In this work, the TLS is a superconducting quantum
circuit whose Rabi oscillations are continuously driven while it is
continuously and weakly measured. The time correlations present at the detector
output agree with quantum-mechanical predictions and violate the inequality by
5 standard deviations.Comment: 26 pages including 10 figures, preprint forma
Kernel Bundle EPDiff: Evolution Equations for Multi-Scale Diffeomorphic Image Registration
International audienceIn the LDDMM framework, optimal warps for image registration are found as end-points of critical paths for an energy functional, and the EPDiff equations describe the evolution along such paths. The Large Deformation Diffeomorphic Kernel Bundle Mapping (LDDKBM) extension of LDDMM allows scale space information to be automatically incorporated in registrations and promises to improve the standard framework in several aspects. We present the mathematical foundations of LDDKBM and derive the KB-EPDiff evolution equations, which provide optimal warps in this new framework. To illustrate the resulting diffeomorphism paths, we give examples showing the decoupled evolution across scales and how the method automatically incorporates deformation at appropriate scales
Frictional Instabilities and Carbonation of Basalts Triggered by Injection of Pressurized H2O- and CO2- Rich Fluids
The safe application of geological carbon storage depends also on the seismic hazard associated with fluid injection. In this regard, we performed friction experiments using a rotary shear apparatus on precut basalts with variable degree of hydrothermal alteration by injecting distilled H2O, pure CO2, and H2O + CO2 fluid mixtures under temperature, fluid pressure, and stress conditions relevant for large-scale subsurface CO2 storage reservoirs. In all experiments, seismic slip was preceded by short-lived slip bursts. Seismic slip occurred at equivalent fluid pressures and normal stresses regardless of the fluid injected and degree of alteration of basalts. Injection of fluids caused also carbonation reactions and crystallization of new dolomite grains in the basalt-hosted faults sheared in H2O + CO2 fluid mixtures. Fast mineral carbonation in the experiments might be explained by shear heating during seismic slip, evidencing the high chemical reactivity of basalts to H2O + CO2 mixtures
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