1,659 research outputs found
Negative response to an excessive bias by a mixed population of voters
We study an outcome of a vote in a population of voters exposed to an
externally applied bias in favour of one of two potential candidates. The
population consists of ordinary individuals, that are in majority and tend to
align their opinion with the external bias, and some number of contrarians ---
individuals who are always hostile to the bias but are not in a conflict with
ordinary voters. The voters interact among themselves, all with all, trying to
find an opinion reached by the community as a whole. We demonstrate that for a
sufficiently weak external bias, the opinion of ordinary individuals is always
decisive and the outcome of the vote is in favour of the preferential
candidate. On the contrary, for an excessively strong bias, the contrarians
dominate in the population's opinion, producing overall a negative response to
the imposed bias. We also show that for sufficiently strong interactions within
the community, either of two subgroups can abruptly change an opinion of the
other group.Comment: 11 pages, 6 figure
Fourier's Law in a Quantum Spin Chain and the Onset of Quantum Chaos
We study heat transport in a nonequilibrium steady state of a quantum
interacting spin chain. We provide clear numerical evidence of the validity of
Fourier law. The regime of normal conductivity is shown to set in at the
transition to quantum chaos.Comment: 4 pages, 5 figures, RevTe
Memory Effects in Nonequilibrium Transport for Deterministic Hamiltonian Systems
We consider nonequilibrium transport in a simple chain of identical
mechanical cells in which particles move around. In each cell, there is a
rotating disc, with which these particles interact, and this is the only
interaction in the model. It was shown in \cite{eckmann-young} that when the
cells are weakly coupled, to a good approximation, the jump rates of particles
and the energy-exchange rates from cell to cell follow linear profiles. Here,
we refine that study by analyzing higher-order effects which are induced by the
presence of external gradients for situations in which memory effects, typical
of Hamiltonian dynamics, cannot be neglected. For the steady state we propose a
set of balance equations for the particle number and energy in terms of the
reflection probabilities of the cell and solve it phenomenologically. Using
this approximate theory we explain how these asymmetries affect various aspects
of heat and particle transport in systems of the general type described above
and obtain in the infinite volume limit the deviation from the theory in
\cite{eckmann-young} to first-order. We verify our assumptions with extensive
numerical simulations.Comment: Several change
Diferencias en actitudes hacia las matemáticas y actitudes matemáticas en estudiantes universitarios de matemáticas e ingeniería
En educación matemática la preocupación y el interés por conocer los factores que obstaculizan o favorecen los procesos de aprendizaje de las matemáticas ha dado lugar a varios estudios. Aunque se reconoce que son muchas las variables que intervienen en el aprendizaje de las matemáticas, para Sánchez y Ursini (2010) "las actitudes han sido consideradas para estudiar este proceso porque… condicionan diversos procesos psicológicos, constituyen parte del sistema de valores del individuo y parecen estar relacionadas con el rendimiento escolar" (p.305). Precisamente en ello radica el interés e importancia de las actitudes. Las actitudes hacia un determinado tema suelen ser estables, ser positivas o negativas, se pueden graduar según su intensidad y expresan sentimientos vinculados a elementos que no son estrictamente parte de una asignatura sino al profesor o tipo de actividad (Estrada, Bazán & Aparicio, 2013)
Labor productivity and natural resources: an assessment at the national level in Honduras
The study establishes the link between agricultural labor productivity and natural resources variables at the national level in Honduras. We show through spatial analysis of productivity and natural resources that the relationship between natural resource conditions and agricultural productivity is not as direct as one can imagine. Length of the rain)" season has a strong and quasi linear relation with income. Soil has little impact on productivity as well as slope and altitude since coffee production in the mountain has a strong relation on productivity. Access to the main cities and to the main seaports has little relation with productivity since some of the main cities are located in unproductive areas. Improving the small road network would have a more positive impact. The study suggests that good research and good policies can have a good impact on productivity
Simulating noisy quantum protocols with quantum trajectories
The theory of quantum trajectories is applied to simulate the effects of
quantum noise sources induced by the environment on quantum information
protocols. We study two models that generalize single qubit noise channels like
amplitude damping and phase flip to the many-qubit situation. We calculate the
fidelity of quantum information transmission through a chaotic channel using
the teleportation scheme with different environments. In this example, we
analyze the role played by the kind of collective noise suffered by the quantum
processor during its operation. We also investigate the stability of a quantum
algorithm simulating the quantum dynamics of a paradigmatic model of chaos, the
baker's map. Our results demonstrate that, using the quantum trajectories
approach, we are able to simulate quantum protocols in the presence of noise
and with large system sizes of more than 20 qubits.Comment: 11 pages, 7 fig
Characterizing SL2S galaxy groups using the Einstein radius
We analyzed the Einstein radius, , in our sample of SL2S galaxy
groups, and compared it with (the distance from the arcs to the center of
the lens), using three different approaches: 1.- the velocity dispersion
obtained from weak lensing assuming a Singular Isothermal Sphere profile
(), 2.- a strong lensing analytical method ()
combined with a velocity dispersion-concentration relation derived from
numerical simulations designed to mimic our group sample, 3.- strong lensing
modeling () of eleven groups (with four new models presented in
this work) using HST and CFHT images. Finally, was analyzed as a function
of redshift to investigate possible correlations with L, N, and the
richness-to-luminosity ratio (N/L). We found a correlation between
and , but with large scatter. We estimate = (2.2 0.9)
+ (0.7 0.2), = (0.4 1.5) + (1.1
0.4), and = (0.4 1.5) + (0.9 0.3) for
each method respectively. We found a weak evidence of anti-correlation between
and , with Log = (0.580.06) - (0.040.1), suggesting
a possible evolution of the Einstein radius with , as reported previously by
other authors. Our results also show that is correlated with L and N
(more luminous and richer groups have greater ), and a possible
correlation between and the N/L ratio. Our analysis indicates that
is correlated with in our sample, making useful to
characterize properties like L and N (and possible N/L) in galaxy groups.
Additionally, we present evidence suggesting that the Einstein radius evolves
with .Comment: Accepted for publication in Astronomy & Astrophysics. Typos correcte
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