12,751 research outputs found
Another analytic view about quantifying social forces
Montroll had considered a Verhulst evolution approach for introducing a
notion he called "social force", to describe a jump in some economic output
when a new technology or product outcompetes a previous one. In fact,
Montroll's adaptation of Verhulst equation is more like an economic field
description than a "social force". The empirical Verhulst logistic function and
the Gompertz double exponential law are used here in order to present an
alternative view, within a similar mechanistic physics framework. As an
example, a "social force" modifying the rate in the number of temples
constructed by a religious movement, the Antoinist community, between 1910 and
1940 in Belgium is found and quantified. Practically, two temple inauguration
regimes are seen to exist over different time spans, separated by a gap
attributed to a specific "constraint", a taxation system, but allowing for a
different, smooth, evolution rather than a jump. The impulse force duration is
also emphasized as being better taken into account within the Gompertz
framework. Moreover, a "social force" can be as here, attributed to a change in
the limited need/capacity of some population, coupled to some external field,
in either Verhulst or Gompertz equation, rather than resulting from already
existing but competing goods as imagined by Montroll.Comment: 4 figures, 29 refs., 15 pages; prepared for Advances in Complex
System
Analytical and numerical studies of disordered spin-1 Heisenberg chains with aperiodic couplings
We investigate the low-temperature properties of the one-dimensional spin-1
Heisenberg model with geometric fluctuations induced by aperiodic but
deterministic coupling distributions, involving two parameters. We focus on two
aperiodic sequences, the Fibonacci sequence and the 6-3 sequence. Our goal is
to understand how these geometric fluctuations modify the physics of the
(gapped) Haldane phase, which corresponds to the ground state of the uniform
spin-1 chain. We make use of different adaptations of the strong-disorder
renormalization-group (SDRG) scheme of Ma, Dasgupta and Hu, widely employed in
the study of random spin chains, supplemented by quantum Monte Carlo and
density-matrix renormalization-group numerical calculations, to study the
nature of the ground state as the coupling modulation is increased. We find no
phase transition for the Fibonacci chain, while we show that the 6-3 chain
exhibits a phase transition to a gapless, aperiodicity-dominated phase similar
to the one found for the aperiodic spin-1/2 XXZ chain. Contrary to what is
verified for random spin-1 chains, we show that different adaptations of the
SDRG scheme may lead to different qualitative conclusions about the nature of
the ground state in the presence of aperiodic coupling modulations.Comment: Accepted for publication in Physical Review
The Anomalous Hall effect in re-entrant AuFe alloys and the real space Berry phase
The Hall effect has been studied in a series of AuFe samples in the
re-entrant concentration range, as well as in the spin glass range. The data
demonstrate that the degree of canting of the local spins strongly modifies the
anomalous Hall effect, in agreement with theoretical predictions associating
canting, chirality and a real space Berry phase. The canonical parametrization
of the Hall signal for magnetic conductors becomes inappropriate when local
spins are canted.Comment: 4 pages, 1 eps figur
First record of Alosa fallax (Lacépède, 1803) (Teleostei: Clupeiformes:Clupeidae) in the Azores Archipelago, Portugal (NE Atlantic)
Copyright © 2014 All rights reserved.This note reports the first record of Alosa fallax (Lacépède, 1803) in the Azores Archipelago (NE Atlantic, Portugal). Being an anadromous species, this occurrence is quite unexpected since there are no suitable breeding habitats for this species in these volcanic islands, isolated and river less. Although A. fallax is known to migrate offshore, it has never been previously reported in oceanic environments. We discuss this occurrence and theorize on the possibility of the species’ being found in Madeira, another Macaronesian Archipelago, albeit much older and closer to European coasts and thus more suitable to be crossed by A. fallax during their migration routes in pelagic environments. With this record, the number of Clupeid fishes for Azorean waters increases to two, the other being the well known and resident Sardina pilchardus
Analytical approach to directed sandpile models on the Apollonian network
We investigate a set of directed sandpile models on the Apollonian network,
which are inspired on the work by Dhar and Ramaswamy (PRL \textbf{63}, 1659
(1989)) for Euclidian lattices. They are characterized by a single parameter
, that restricts the number of neighbors receiving grains from a toppling
node. Due to the geometry of the network, two and three point correlation
functions are amenable to exact treatment, leading to analytical results for
the avalanche distributions in the limit of an infinite system, for .
The exact recurrence expressions for the correlation functions are numerically
iterated to obtain results for finite size systems, when larger values of
are considered. Finally, a detailed description of the local flux properties is
provided by a multifractal scaling analysis.Comment: 7 pages in two-column format, 10 illustrations, 5 figure
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