19,101 research outputs found
Is Employment Globalizing?
We investigate the claim that national labor markets have become more globally interconnected in recent decades. We do so by deriving estimates over time of three different notions of interconnection: (i) the share of labor demand that is export induced (i.e., all labor demand created by foreign entities buying products exported by the home country)—we provide estimates for 40 countries; (ii) the share of workers employed in sectors producing tradable goods or services—68 countries; and (iii) the ratio of the number of jobs that are either located in a tradable sector, or that are involved in producing services that are required by these tradable sectors, to all jobs in the economy, which we call the trade-linked employment share—40 countries. Our estimates lead to the conclusion that the evidence of a large increase in the interconnections between national labor markets is far weaker than commonly asserted: levels of interconnectivity, and the direction of changes over time, vary across notions of interconnection and countries. The main reasons for this are labor- displacing productivity growth in tradable sectors of each economy and the diminishing fraction of national labor forces hired into manufacturing jobs worldwide. We also discuss the implications of our results for different policy debates that each of the three measures is associated with: international coordination of macroeconomic policies (export-induced labor demand), currency devaluations (share of workers producing tradables), and education and labor protection (trade-linked share)
A Universal Interacting Crossover Regime in Two-Dimensional Quantum Dots
Interacting electrons in quantum dots with large Thouless number in the
three classical random matrix symmetry classes are well-understood. When a
specific type of spin-orbit coupling known to be dominant in two dimensional
semiconductor quantum dots is introduced, we show that a new interacting
quantum critical crossover energy scale emerges and low-energy quasiparticles
generically have a decay width proportional to their energy. The low-energy
physics of this system is an example of a universal interacting crossover
regime.Comment: 4 pages, 1 figur
Kuramoto model with coupling through an external medium
Synchronization of coupled oscillators is often described using the Kuramoto
model. Here we study a generalization of the Kuramoto model where oscillators
communicate with each other through an external medium. This generalized model
exhibits interesting new phenomena such as bistability between synchronization
and incoherence and a qualitatively new form of synchronization where the
external medium exhibits small-amplitude oscillations. We conclude by
discussing the relationship of the model to other variations of the Kuramoto
model including the Kuramoto model with a bimodal frequency distribution and
the Millennium Bridge problem.Comment: 9 pages, 3 figure
Virus isolation studies suggest short-term variations in abundance in natural cyanophage populations of the Indian Ocean
Cyanophage abundance has been shown to fluctuate over long timescales and with depth, but little is known about how it varies over short timescales. Previous short-term studies have relied on counting total virus numbers and therefore the phages which infect cyanobacteria cannot be distinguished from the total count.
In this study, an isolation-based approach was used to determine cyanophage abundance from water samples collected over a depth profile for a 24 h period from the Indian Ocean. Samples were used to infect Synechococcus sp. WH7803 and the number of plaque forming units (pfu) at each time point and depth were counted. At 10 m phage numbers were similar for most time-points, but there was a distinct peak in abundance at 0100 hours. Phage numbers were lower at 25 m and 50 m and did not show such strong temporal variation. No phages were found below this depth. Therefore, we conclude that only the abundance of phages in surface waters showed a clear temporal pattern over a short timescale. Fifty phages from a range of depths and time points were isolated and purified. The molecular diversity of these phages was estimated using a section of the phage-encoded psbD gene and the results from a phylogenetic analysis do not suggest that phages from the deeper waters form a distinct subgroup
Modelling highway-traffic headway distributions using superstatistics
We study traffic clearance distributions (i.e., the instantaneous gap between
successive vehicles) and time headway distributions by applying Beck and
Cohen's superstatistics. We model the transition from free phase to congested
phase with the increase of vehicle density as a transition from the Poisson
statistics to that of the random matrix theory. We derive an analytic
expression for the spacing distributions that interpolates from the Poisson
distribution and Wigner's surmise and apply it to the distributions of the nett
distance and time gaps among the succeeding cars at different densities of
traffic flow. The obtained distribution fits the experimental results for
single-vehicle data of the Dutch freeway A9 and the German freeway A5.Comment: 10 pages, 2 figure
Phenomenological model for symmetry breaking in chaotic system
We assume that the energy spectrum of a chaotic system undergoing symmetry
breaking transitions can be represented as a superposition of independent level
sequences, one increasing on the expense of the others. The relation between
the fractional level densities of the sequences and the symmetry breaking
interaction is deduced by comparing the asymptotic expression of the
level-number variance with the corresponding expression obtained using the
perturbation theory. This relation is supported by a comparison with previous
numerical calculations. The predictions of the model for the
nearest-neighbor-spacing distribution and the spectral rigidity are in
agreement with the results of an acoustic resonance experiment.Comment: accepted for publication in Physical Review
Superstatistical random-matrix-theory approach to transition intensities in mixed systems
We study the fluctuation properties of transition intensities applying a
recently proposed generalization of the random matrix theory, which is based on
Beck and Cohen's superstatistics. We obtain an analytic expression for the
distribution of the reduced transition probabilities that applies to systems
undergoing a transition out of chaos. The obtained distribution fits the
results of a previous nuclear shell model calculations for some electromagnetic
transitions that deviate from the Porter-Thomas distribution. It agrees with
the experimental reduced transition probabilities for the 26A nucleus better
than the commonly used chi-squared distribution.Comment: 14 pages, 3 figure
Does dynamics reflect topology in directed networks?
We present and analyze a topologically induced transition from ordered,
synchronized to disordered dynamics in directed networks of oscillators. The
analysis reveals where in the space of networks this transition occurs and its
underlying mechanisms. If disordered, the dynamics of the units is precisely
determined by the topology of the network and thus characteristic for it. We
develop a method to predict the disordered dynamics from topology. The results
suggest a new route towards understanding how the precise dynamics of the units
of a directed network may encode information about its topology.Comment: 7 pages, 4 figures, Europhysics Letters, accepte
Quantum criticality near the Stoner transition in a two-dot with spin-orbit coupling
We study a system of two tunnel-coupled quantum dots, with the first dot
containing interacting electrons (described by the Universal Hamiltonian) not
subject to spin-orbit coupling, whereas the second contains non-interacting
electrons subject to spin-orbit coupling. We focus on describing the behavior
of the system near the Stoner transition. Close to the critical point quantum
fluctuations become important and the system enters a quantum critical regime.
The large- approximation allows us to calculate physical quantitites
reliably even in this strongly fluctuating regime. In particular, we find a
scaling function to describe the crossover of the quasiparticle decay rate
between the renormalized Fermi liquid regime and the quantum critical regime.Comment: 19 pages, 5 figure
Weak Measurements with Arbitrary Pointer States
The exact conditions on valid pointer states for weak measurements are
derived. It is demonstrated that weak measurements can be performed with any
pointer state with vanishing probability current density. This condition is
found both for weak measurements of noncommuting observables and for -number
observables. In addition, the interaction between pointer and object must be
sufficiently weak. There is no restriction on the purity of the pointer state.
For example, a thermal pointer state is fully valid.Comment: 4 page
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