14,047 research outputs found
Counterions at charge-modulated substrates
We consider counterions in the presence of a single planar surface with a
spatially inhomogeneous charge distribution using Monte-Carlo simulations and
strong-coupling theory. For high surface charges, multivalent counterions, or
pronounced substrate charge modulation the counterions are laterally correlated
with the surface charges and their density profile deviates strongly from the
limit of a smeared-out substrate charge distribution, in particular exhibiting
a much increased laterally averaged density at the surface.Comment: 7 page
Micro-bias and macro-performance
We use agent-based modeling to investigate the effect of conservatism and
partisanship on the efficiency with which large populations solve the density
classification task--a paradigmatic problem for information aggregation and
consensus building. We find that conservative agents enhance the populations'
ability to efficiently solve the density classification task despite large
levels of noise in the system. In contrast, we find that the presence of even a
small fraction of partisans holding the minority position will result in
deadlock or a consensus on an incorrect answer. Our results provide a possible
explanation for the emergence of conservatism and suggest that even low levels
of partisanship can lead to significant social costs.Comment: 11 pages, 5 figure
Wigner-Crystal Formulation of Strong-Coupling Theory for Counter-ions Near Planar Charged Interfaces
We present a new analytical approach to the strong electrostatic coupling
regime (SC), that can be achieved equivalently at low temperatures, high
charges, low dielectric permittivity etc. Two geometries are analyzed in
detail: one charged wall first, and then, two parallel walls at small
distances, that can be likely or oppositely charged. In all cases, one type of
mobile counter-ions only is present, and ensures electroneutrality (salt free
case). The method is based on a systematic expansion around the ground state
formed by the two-dimensional Wigner crystal(s) of counter-ions at the
plate(s). The leading SC order stems from a single-particle theory, and
coincides with the virial SC approach that has been much studied in the last 10
years. The first correction has the functional form of the virial SC
prediction, but the prefactor is different. The present theory is free of
divergences and the obtained results, both for symmetrically and asymmetrically
charged plates, are in excellent agreement with available data of Monte-Carlo
simulations under strong and intermediate Coulombic couplings. All results
obtained represent relevant improvements over the virial SC estimates. The
present SC theory starting from the Wigner crystal and therefore coined Wigner
SC, sheds light on anomalous phenomena like the counter-ion mediated
like-charge attraction, and the opposite-charge repulsion
Non-Local Product Rules for Percolation
Despite original claims of a first-order transition in the product rule model
proposed by Achlioptas et al. [Science 323, 1453 (2009)], recent studies
indicate that this percolation model, in fact, displays a continuous
transition. The distinctive scaling properties of the model at criticality,
however, strongly suggest that it should belong to a different universality
class than ordinary percolation. Here we introduce a generalization of the
product rule that reveals the effect of non-locality on the critical behavior
of the percolation process. Precisely, pairs of unoccupied bonds are chosen
according to a probability that decays as a power-law of their Manhattan
distance, and only that bond connecting clusters whose product of their sizes
is the smallest, becomes occupied. Interestingly, our results for
two-dimensional lattices at criticality shows that the power-law exponent of
the product rule has a significant influence on the finite-size scaling
exponents for the spanning cluster, the conducting backbone, and the cutting
bonds of the system. In all three cases, we observe a continuous variation from
ordinary to (non-local) explosive percolation exponents.Comment: 5 pages, 4 figure
Production of exotic charmonium in interactions at hadronic colliders
In this paper we investigate the Exotic Charmonium (EC) production in interactions present in proton-proton, proton-nucleus and
nucleus-nucleus collisions at the CERN Large Hadron Collider (LHC) energies as
well as for the proposed energies of the Future Circular Collider (FCC). Our
results demonstrate that the experimental study of these processes is feasible
and can be used to constrain the theoretical decay widths and shed some light
on the configuration of the considered multiquark states.Comment: 7 pages, 2 figures, 3 tables. v2: Revised version published in
Physical Review
Universal reduction of pressure between charged surfaces by long-wavelength surface charge modulation
We predict theoretically that long-wavelength surface charge modulations
universally reduce the pressure between the charged surfaces with counterions
compared with the case of uniformly charged surfaces with the same average
surface charge density. The physical origin of this effect is the fact that
surface charge modulations always lead to enhanced counterion localization near
the surfaces, and hence, fewer charges at the midplane. We confirm the last
prediction with Monte Carlo simulations.Comment: 8 pages 1 figure, Europhys. Lett., in pres
Dinâmica da matéria orgânica na recuperação de clareiras da floresta amazônica.
O objetivo deste trabalho foi avaliar a dinâmica da matĂ©ria orgânica e da biomassa microbiana em áreas de reflorestamento com 0, 1, 2, 4 e 10 anos de idade realizados na provĂncia petrolĂfera do rio Urucu, localizada no municĂpio de Coari, regiĂŁo central do Estado do Amazonas
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