4,792 research outputs found
From the lab to the field: envelopes, dictators and manners
Results are reported of the first natural field experiment on the dictator game, where subjects are unaware that they participate in an experiment. In contrast to predictions of the standard economic model, dictators show a large degree of pro-social behavior. This paper builds a bridge from the laboratory to the field to explore how predictive findings from the laboratory are for the field. External validity is remarkably high. In all experiments, subjects display an equally high amount of pro-social behavior, whether they are students or not, participate in a laboratory or not, or are aware that they participate in an experiment or not.altruism, natural field experiment, external validity
Auditory power-law activation-avalanches exhibit a fundamental computational ground-state
The cochlea provides a biological information-processing paradigm that we
only begin to under- stand in its full complexity. Our work reveals an
interacting network of strongly nonlinear dynami- cal nodes, on which even
simple sound input triggers subnetworks of activated elements that follow
power-law size statistics ('avalanches'). From dynamical systems theory,
power-law size distribu- tions relate to a fundamental ground-state of
biological information processing. Learning destroys these power laws. These
results strongly modify the models of mammalian sound processing and provide a
novel methodological perspective for understanding how the brain processes
information.Comment: Videos are not included, please ask author
Kibble-Zurek mechanism in curved elastic surface crystals
Topological defects shape the material and transport properties of physical
systems. Examples range from vortex lines in quantum superfluids,
defect-mediated buckling of graphene, and grain boundaries in ferromagnets and
colloidal crystals, to domain structures formed in the early universe. The
Kibble-Zurek (KZ) mechanism describes the topological defect formation in
continuous non-equilibrium phase transitions with a constant finite quench
rate. Universal KZ scaling laws have been verified experimentally and
numerically for second-order transitions in planar Euclidean geometries, but
their validity for discontinuous first-order transitions in curved and
topologically nontrivial systems still poses an open question. Here, we use
recent experimentally confirmed theory to investigate topological defect
formation in curved elastic surface crystals formed by stress-quenching a
bilayer material. Studying both spherical and toroidal crystals, we find that
the defect densities follow KZ-type power laws independent of surface geometry
and topology. Moreover, the nucleation sequences agree with recent experimental
observations for spherical colloidal crystals. These results suggest that KZ
scaling laws hold for a much broader class of dynamical phase transitions than
previously thought, including non-thermal first-order transitions in non-planar
geometries.Comment: 8 pages, 3 figures; introduction and typos correcte
Nonlinear buckling and symmetry breaking of a soft elastic sheet sliding on a cylindrical substrate
We consider the axial compression of a thin sheet wrapped around a rigid
cylindrical substrate. In contrast to the wrinkling-to-fold transitions
exhibited in similar systems, we find that the sheet always buckles into a
single symmetric fold, while periodic solutions are unstable. Upon further
compression, the solution breaks symmetry and stabilizes into a recumbent fold.
Using linear analysis and numerics, we theoretically predict the buckling force
and energy as a function of the compressive displacement. We compare our theory
to experiments employing cylindrical neoprene sheets and find remarkably good
agreement.Comment: 20 pages, 5 figure
Clogging and Jamming of Colloidal Monolayers Driven Across a Disordered Landscape
We experimentally investigate the clogging and jamming of interacting
paramagnetic colloids driven through a quenched disordered landscape of fixed
obstacles. When the particles are forced to cross a single aperture between two
obstacles, we find an intermittent dynamics characterized by an exponential
distribution of burst size. At the collective level, we observe that quenched
disorder decreases the particle ow, but it also greatly enhances the "faster is
slower" effect, that occurs when increasing the particle speed. Further, we
show that clogging events may be controlled by tuning the pair interactions
between the particles during transport, such that the colloidal ow decreases
for repulsive interactions, but increases for anisotropic attraction. We
provide an experimental test-bed to investigate the crucial role of disorder on
clogging and jamming in driven microscale matter
Natural data structure extracted from neighborhood-similarity graphs
'Big' high-dimensional data are commonly analyzed in low-dimensions, after
performing a dimensionality-reduction step that inherently distorts the data
structure. For the same purpose, clustering methods are also often used. These
methods also introduce a bias, either by starting from the assumption of a
particular geometric form of the clusters, or by using iterative schemes to
enhance cluster contours, with uncontrollable consequences. The goal of data
analysis should, however, be to encode and detect structural data features at
all scales and densities simultaneously, without assuming a parametric form of
data point distances, or modifying them. We propose a novel approach that
directly encodes data point neighborhood similarities as a sparse graph. Our
non-iterative framework permits a transparent interpretation of data, without
altering the original data dimension and metric. Several natural and synthetic
data applications demonstrate the efficacy of our novel approach
Two universal physical principles shape the power-law statistics of real-world networks
The study of complex networks has pursued an understanding of macroscopic
behavior by focusing on power-laws in microscopic observables. Here, we uncover
two universal fundamental physical principles that are at the basis of complex
networks generation. These principles together predict the generic emergence of
deviations from ideal power laws, which were previously discussed away by
reference to the thermodynamic limit. Our approach proposes a paradigm shift in
the physics of complex networks, toward the use of power-law deviations to
infer meso-scale structure from macroscopic observations.Comment: 14 pages, 7 figure
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