13,015 research outputs found
Impact of Social Media on Economic Growth - Evidence from Social Media
This paper attempts to investigate the impact of social media on economic growth. Using information obtained from memberships to social networks, we find that social media has a negative and significant impact on economic growth. This provides evidence in favour of our hypothesis that social media increases the search costs for information and also increases the substitution effect from labour to leisure thereby producing a negative impact on growth
Chaotic diffusion of particles with finite mass in oscillating convection flows
Deterministic diffusion in temporally oscillating convection is studied for
particles with finite mass. The particles are assumed to obey a simple
dissipative dynamical system and the particle diffusion is induced by the
strange attractor. The diffusion constants are numerically calculated for
convection models with free and rigid boundary conditions.Comment: 5 figure
Martian surface physical properties to be derived by radar altimeter on the Mars observer spacecraft
The potential is described of a candidate Mars Observer altimeter for determining dielectric properties of Mars regolith. It is pointed out that it is straightforward to use the time between altimeter pulse trains for passive radiometry (hence dielectric properties) and roughness can be derived. Given the mission plan the whole surface can be mapped at least three times, yielding data on seasonal variability
Spin-squeezed Ground States in the Bilayer Quantum Hall Ferromagnet
A "squeezed-vacuum" state considered in quantum optics is shown to be
realized in the ground-state wavefunction for the bilayer quantum Hall system
at the total Landau level filling of (m: odd integer). This is
derived in the boson approximation, where a particle-hole pair creation across
the symmetric-antisymmetric gap, , is regarded as a boson. In
terms of the pseudospin describing the layers, the state is a spin-squeezed
state, where the degree of squeezing is controlled by the layer separation and
. An exciton condensation, which amounts to a rotated
spin-squeezed state, has a higher energy due to the degraded SU(2) symmetry for
.Comment: 4 pages, revtex, one figure, to appear in PRB Rapid Communicatio
Variable Step Random Walks and Self-Similar Distributions
We study a scenario under which variable step random walks give anomalous
statistics. We begin by analyzing the Martingale Central Limit Theorem to find
a sufficient condition for the limit distribution to be non-Gaussian. We note
that the theorem implies that the scaling index is 1/2. For
corresponding continuous time processes, it is shown that the probability
density function satisfies the Fokker-Planck equation. Possible forms
for the diffusion coefficient are given, and related to . Finally, we
show how a time-series can be used to distinguish between these variable
diffusion processes and L\'evy dynamics.Comment: 13pages, 2 figure
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