3,272 research outputs found
Singularities of the susceptibility of an SRB measure in the presence of stable-unstable tangencies
Let be an SRB (or "physical"), measure for the discrete time evolution
given by a map , and let denote the expectation value of a smooth
function . If depends on a parameter, the derivative of
with respect to the parameter is formally given by the value of the
so-called susceptibility function at . When is a uniformly
hyperbolic diffeomorphism, it has been proved that the power series
has a radius of convergence , and that , but
it is known that in some other cases. One reason why may fail
to be uniformly hyperbolic is if there are tangencies between the stable and
unstable manifolds for . The present paper gives a crude,
nonrigorous, analysis of this situation in terms of the Hausdorff dimension
of in the stable direction. We find that the tangencies produce
singularities of for if
. In particular, if we may hope that makes sense, and
the derivative has thus a chance to be definedComment: 12 page
Simultaneous Continuation of Infinitely Many Sinks Near a Quadratic Homoclinic Tangency
We prove that the diffeomorphisms on surfaces, exhibiting infinitely
many sinksnear the generic unfolding of a quadratic homoclinic tangency of a
dissipative saddle, can be perturbed along an infinite dimensional manifold of
diffeomorphisms such that infinitely many sinks persist simultaneously.
On the other hand, if they are perturbed along one-parameter families that
unfold generically the quadratic tangencies, then at most a finite number of
those sinks have continuation
Creative fictions: Incentive work and humanitarian labour in South Sudan
The career of the incentive has been meteoric and global, cropping up in peace‐building, state‐building, global health, and humanitarian contexts across the world. In this paper, I consider incentive work from the vantage point of independence‐era South Sudan. In doing so, I build conversations between geography and spatially sensitive anthropology about the power of social forms to shape action, through an attention to the porous and polyvalent logics of legitimation entailed in ‘creative fictions’. Attention to the modes of legitimation help to understand not only what social forms do, but also how they emerge, travel, and are appropriated and repurposed for use by new sets of actors. In tracing the transit of incentive work from development practice into humanitarian programming, I understand incentive work as a creative fiction—an intangible social form that animates and channels action to generative ends. While incentive work emerged as a tidy solution to constraints within the humanitarian sector on who might be paid for what kind work, the social form of incentive work proliferated. Set free from those constraints, incentive work offered up channels of accumuclation to new actors—including mid‐level state functionaries—by mobilizing and ligitimating claims on un‐ and under‐compensated labour though a call to voluntas, the morally inflected volitional ethos of volunteerism
For Richer or For Poorer? Evidence from Indonesia, South Africa, Spain, and Venezuela
We analyze household income dynamics using longitudinal data from Indonesia, South Africa (KwaZulu-Natal), Spain and Venezuela. In all four countries, households with the lowest reported base-year income experienced the largest absolute income gains. This result is robust to reasonable amounts of measurement error in two of the countries. In three of the four countries, households with the lowest predicted base-year income experienced gains at least as large as their wealthier counterparts. Thus, with one exception, the empirical importance of cumulative advantage, poverty traps, and skill-biased technical change was no greater than structural or macroeconomic changes that favored initially poor households in these four countries
Randomised feasibility study of a novel experience-based internet intervention to support self-management in chronic asthma.
ElectronicPeer reviewedPublisher PD
Reaction kinetics on clusters and islands
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70583/2/JCPSA6-85-11-6804-1.pd
Absence of kinetic effects in reaction-diffusion processes in scale-free networks
We show that the chemical reactions of the model systems of A+A->0 and A+B->0
when performed on scale-free networks exhibit drastically different behavior as
compared to the same reactions in normal spaces. The exponents characterizing
the density evolution as a function of time are considerably higher than 1,
implying that both reactions occur at a much faster rate. This is due to the
fact that the discerning effects of the generation of a depletion zone (A+A)
and the segregation of the reactants (A+B) do not occur at all as in normal
spaces. Instead we observe the formation of clusters of A (A+A reaction) and of
mixed A and B (A+B reaction) around the hubs of the network. Only at the limit
of very sparse networks is the usual behavior recovered.Comment: 4 pages, 4 figures, to be published in Physical Review Letter
Infinitely Many Stochastically Stable Attractors
Let f be a diffeomorphism of a compact finite dimensional boundaryless
manifold M exhibiting infinitely many coexisting attractors. Assume that each
attractor supports a stochastically stable probability measure and that the
union of the basins of attraction of each attractor covers Lebesgue almost all
points of M. We prove that the time averages of almost all orbits under random
perturbations are given by a finite number of probability measures. Moreover
these probability measures are close to the probability measures supported by
the attractors when the perturbations are close to the original map f.Comment: 14 pages, 2 figure
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