4,173 research outputs found
Tactical Voting in Plurality Elections
How often will elections end in landslides? What is the probability for a
head-to-head race? Analyzing ballot results from several large countries rather
anomalous and yet unexplained distributions have been observed. We identify
tactical voting as the driving ingredient for the anomalies and introduce a
model to study its effect on plurality elections, characterized by the relative
strength of the feedback from polls and the pairwise interaction between
individuals in the society. With this model it becomes possible to explain the
polarization of votes between two candidates, understand the small margin of
victories frequently observed for different elections, and analyze the polls'
impact in American, Canadian, and Brazilian ballots. Moreover, the model
reproduces, quantitatively, the distribution of votes obtained in the Brazilian
mayor elections with two, three, and four candidates.Comment: 7 pages, 4 figure
Direct evidence for charge stripes in a layered cobalt oxide
Recent experiments indicate that static stripe-like charge order is generic to the hole-doped copper oxide superconductors and competes with superconductivity. Here we show that a similar type of charge order is present in La5/3 Sr1/3 CoO4 , an insulating analogue of the copper oxide superconductors containing cobalt in place of copper. The stripe phase we have detected is accompanied by short-range, quasi-one-dimensional, antiferromagnetic order, and provides a natural explanation for the distinctive hour- glass shape of the magnetic spectrum previously observed in neutron scattering mea- surements of La2âxSrx CoO4 and many hole-doped copper oxide superconductors. The results establish a solid empirical basis for theories of the hourglass spectrum built on short-range, quasi-static, stripe correlations
Biological, biochemical and molecular features of Trypanosoma cruzi strains isolated from patients infected through oral transmission during a 2005 outbreak in the state of Santa Catarina, Brazil: its correspondence with the new T. cruzi Taxonomy Consensus (2009)
Particle separation in surface acoustic wave microfluidic devices using reprogrammable, pseudo-standing waves
We report size and density/compressibility-based particle sorting using on-off quasi-standing
waves based on the frequency difference between two ultrasonic transducers. The 13.3 MHz fundamental operating frequency of the surface acoustic wave microfluidic device allows the manipulation of particles on the micrometer scale. Experiments, validated by computational fluid dynamics,
were carried out to demonstrate size-based sorting of 5â14.5 lm diameter polystyrene (PS) particles and density/compressibility-based sorting of 10 lm PS, iron-oxide, and poly(methyl methacrylate) particles, with densities ranging from 1.05 to 1.5 g/cm3
. The method shows a sorting
efficiency of >90% and a purity of >80% for particle separation of 10 lm and 14.5 lm, demonstrating better performance than similar sorting methods recently published (72%â83% efficiency).
The sorting technique demonstrates high selectivity separation of particles, with the smallest particle ratio being 1.33, compared to 2.5 in previous work. Density/compressibility-based sorting of
polystyrene and iron-oxide particles showed an efficiency of 97 6 4% and a purity of 91 6 5%. By
varying the sign of the acoustic excitation signal, continuous batch acoustic sorting of target particles to a desired outlet was demonstrated with good sorting stability against variations of the
inflow rate
Gravitational energy of a magnetized Schwarzschild black hole - a teleparallel approach
We investigate the distribution of gravitational energy on the spacetime of a
Schwarzschild black hole immersed in a cosmic magnetic field. This is done in
the context of the {\it Teleparallel Equivalent of General Relativity}, which
is an alternative geometrical formulation of General Relativity, where gravity
is describe by a spacetime endowed with torsion, rather than curvature, with
the fundamental field variables being tetrads. We calculate the energy enclosed
by a two-surface of constant radius - in particular, the energy enclosed by the
event horizon of the black hole. In this case we find that the magnetic field
has the effect of increasing the gravitational energy as compared to the vacuum
Schwarzschild case. We also compute the energy (i) in the weak magnetic field
limit, (ii) in the limit of vanishing magnetic field, and (iii) in the absence
of the black hole. In all cases our results are consistent with what should be
expected on physical grounds.Comment: version to match the one to be published on General Relativity and
Gravitatio
Gauss-Bonnet Black Holes and Heavy Fermion Metals
We consider charged black holes in Einstein-Gauss-Bonnet Gravity with
Lifshitz boundary conditions. We find that this class of models can reproduce
the anomalous specific heat of condensed matter systems exhibiting
non-Fermi-liquid behaviour at low temperatures. We find that the temperature
dependence of the Sommerfeld ratio is sensitive to the choice of Gauss-Bonnet
coupling parameter for a given value of the Lifshitz scaling parameter. We
propose that this class of models is dual to a class of models of
non-Fermi-liquid systems proposed by Castro-Neto et.al.Comment: 17 pages, 6 figures, pdfLatex; small corrections to figure 10 in this
versio
No chiral truncation of quantum log gravity?
At the classical level, chiral gravity may be constructed as a consistent
truncation of a larger theory called log gravity by requiring that left-moving
charges vanish. In turn, log gravity is the limit of topologically massive
gravity (TMG) at a special value of the coupling (the chiral point). We study
the situation at the level of linearized quantum fields, focussing on a unitary
quantization. While the TMG Hilbert space is continuous at the chiral point,
the left-moving Virasoro generators become ill-defined and cannot be used to
define a chiral truncation. In a sense, the left-moving asymptotic symmetries
are spontaneously broken at the chiral point. In contrast, in a non-unitary
quantization of TMG, both the Hilbert space and charges are continuous at the
chiral point and define a unitary theory of chiral gravity at the linearized
level.Comment: 20 pages, no figures, references adde
Holography For a De Sitter-Esque Geometry
Warped dS arises as a solution to topologically massive gravity (TMG)
with positive cosmological constant and Chern-Simons coefficient
in the region . It is given by a real line fibration
over two-dimensional de Sitter space and is equivalent to the rotating Nariai
geometry at fixed polar angle. We study the thermodynamic and asymptotic
structure of a family of geometries with warped dS asymptotics.
Interestingly, these solutions have both a cosmological horizon and an internal
one, and their entropy is unbounded from above unlike black holes in regular de
Sitter space. The asymptotic symmetry group resides at future infinity and is
given by a semi-direct product of a Virasoro algebra and a current algebra. The
right moving central charge vanishes when . We discuss the
possible holographic interpretation of these de Sitter-esque spacetimes.Comment: 22 pages, 1 figure; v2: typos corrected, to match with published
versio
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