15,426 research outputs found
Self-organizing social hierarchies on scale-free networks
In this work we extend the model of Bonabeau et al. in the case of scale-free
networks. A sharp transition is observed from an egalitarian to an hierarchical
society, with a very low population density threshold. The exact threshold
value also depends on the network size. We find that in an hierarchical society
the number of individuals with strong winning attitude is much lower than the
number of the community members that have a low winning probability
Reshuffling spins with short range interactions: When sociophysics produces physical results
Galam reshuffling introduced in opinion dynamics models is investigated under
the nearest neighbor Ising model on a square lattice using Monte Carlo
simulations. While the corresponding Galam analytical critical temperature T_C
\approx 3.09 [J/k_B] is recovered almost exactly, it is proved to be different
from both values, not reshuffled (T_C=2/arcsinh(1) \approx 2.27 [J/k_B]) and
mean-field (T_C=4 [J/k_B]). On this basis, gradual reshuffling is studied as
function of 0 \leq p \leq 1 where p measures the probability of spin
reshuffling after each Monte Carlo step. The variation of T_C as function of p
is obtained and exhibits a non-linear behavior. The simplest Solomon network
realization is noted to reproduce Galam p=1 result. Similarly to the critical
temperature, critical exponents are found to differ from both, the classical
Ising case and the mean-field values.Comment: 11 pages, 5 figures in 6 eps files, to appear in IJMP
CVD of CrO2: towards a lower temperature deposition process
We report on the synthesis of highly oriented a-axis CrO2 films onto (0001)
sapphire by atmospheric pressure CVD from CrO3 precursor, at growth
temperatures down to 330 degree Celsius, i.e. close to 70 degrees lower than in
published data for the same chemical system. The films keep the high quality
magnetic behaviour as those deposited at higher temperature, which can be
looked as a promising result in view of their use with thermally sensitive
materials, e.g. narrow band gap semiconductors.Comment: 13 pages, 4 figure
Modelling formation and evolution of transverse dune fields
We model formation and evolution of transverse dune fields. In the model,
only the cross section of the dune is simulated. The only physical variable of
relevance is the dune height, from which the dune width and velocity are
determined, as well as phenomenological rules for interaction between two dunes
of different heights. We find that dune fields with no sand on the ground
between dunes are unstable, i.e. small dunes leave the higher ones behind. We
then introduce a saturation length to simulate transverse dunes on a sand bed
and show that this leads to stable dune fields with regular spacing and dune
heights. Finally, we show that our model can be used to simulate coastal dune
fields if a constant sand influx is considered, where the dune height increases
with the distance from the beach, reaching a constant value.Comment: 18 pages including 9 figure
Electrical activation and electron spin coherence of ultra low dose antimony implants in silicon
We implanted ultra low doses (2x10^11 cm-2) of 121Sb ions into isotopically
enriched 28Si and find high degrees of electrical activation and low levels of
dopant diffusion after rapid thermal annealing. Pulsed Electron Spin Resonance
shows that spin echo decay is sensitive to the dopant depths, and the interface
quality. At 5.2 K, a spin decoherence time, T2, of 0.3 ms is found for profiles
peaking 50 nm below a Si/SiO2 interface, increasing to 0.75 ms when the surface
is passivated with hydrogen. These measurements provide benchmark data for the
development of devices in which quantum information is encoded in donor
electron spins
High fidelity one-qubit operations under random telegraph noise
We address the problem of implementing high fidelity one-qubit operations
subject to time dependent noise in the qubit energy splitting. We show with
explicit numerical results that high fidelity bit flips and one-qubit NOT gates
may be generated by imposing bounded control fields. For noise correlation
times shorter than the time for a pi-pulse, the time optimal pi-pulse yields
the highest fidelity. For very long correlation times, fidelity loss is
approximately due to systematic error, which is efficiently tackled by
compensation for off-resonance with a pulse sequence (CORPSE). For intermediate
ranges of the noise correlation time we find that short CORPSE, which is less
accurate than CORPSE in correcting systematic errors, yields higher fidelities.
Numerical optimization of the pulse sequences using gradient ascent pulse
engineering results in noticeable improvement of the fidelities for the bit
flip and marginal improvement for the NOT gate.Comment: 7 pages, 6 figure
Efeito de diferentes solventes orgânicos sobre a viabilidade do pólen de jerivá (Syagrus romanzoffiana S. CHAM).
EVINCI. Resumo
Avaliação genômica de Piper yellow mottle virus da pimenteira do reino (Piper nigrum L.).
Edição dos resumos do 44º Congresso Brasileiro de Fitopatologia, 2011, Bento Gonçalves. Resumo 776
Pseudoscalars Mesons in Hot, Dense Matter
Phase transitions in hot and dense matter and the in--medium behavior of
pseudoscalar mesons () are investigated, in the framework of the three flavor Nambu--Jona-Lasinio
model, including the 't Hooft interaction, which breaks the symmetry.
Three different scenarios are considered: zero density and finite temperature,
zero temperature and finite density in quark matter with different degrees of
strangeness, and finite temperature and density. At T=0, the role of strange
valence quarks in the medium is discussed, in connection with the phase
transition and the mesonic behavior. It is found that the appearance of strange
quarks, above certain densities, leads to meaningful changes in different
observables, especially in matter with \betaT-\rho$ plane is analyzed in connection with possible signatures
of restoration of symmetries.Comment: 33 pages, 12 figures, PRC versio
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