7 research outputs found
Coevolving nonlinear voter model with triadic closure
We study a nonlinear coevolving voter model with triadic closure local
rewiring. We find three phases with different topological properties and
configuration in the steady state: absorbing consensus phase with a single
component, absorbing fragmented phase with two components in opposite consensus
states, and a dynamically active shattered phase with many isolated nodes. This
shattered phase, which does not exist for a coevolving model with global
rewiring, has a lifetime that scale exponentially with system size. We
characterize the transitions between these phases in terms of the size of the
largest cluster, the number of clusters, and the magnetization. Our analysis
provides a possible solution to reproduce isolated parts in adaptive networks
and high clustering widely observed in social systems
Ordering dynamics in the voter model with aging
The voter model with memory-dependent dynamics is theoretically and
numerically studied at the mean-field level. The `internal age', or time an
individual spends holding the same state, is added to the set of binary states
of the population, such that the probability of changing state (or activation
probability ) depends on this age. A closed set of integro-differential
equations describing the time evolution of the fraction of individuals with a
given state and age is derived, and from it analytical results are obtained
characterizing the behavior of the system close to the absorbing states. In
general, different age-dependent activation probabilities have different
effects on the dynamics. When the activation probability is an increasing
function of the age , the system reaches a steady state with coexistence of
opinions. In the case of aging, with being a decreasing function, either
the system reaches consensus or it gets trapped in a frozen state, depending on
the value of (zero or not) and the velocity of approaching
. Moreover, when the system reaches consensus, the time ordering of
the system can be exponential () or power-law like ().
Exact conditions for having one or another behavior, together with the
equations and explicit expressions for the exponents, are provided
Emergence of complex structures from nonlinear interactions and noise in coevolving networks
We study the joint effect of the non-linearity of interactions and noise on
coevolutionary dynamics. We choose the coevolving voter model as a prototype
framework for this problem. By numerical simulations and analytical
approximations we find three main phases that differ in the absolute
magnetization and the size of the largest component: a consensus phase, a
coexistence phase, and a dynamical fragmentation phase. More detailed analysis
reveals inner differences in these phases, allowing us to divide two of them
further. In the consensus phase we can distinguish between a weak or
alternating consensus (switching between two opposite consensus states), and a
strong consensus, in which the system remains in the same state for the whole
realization of the stochastic dynamics. Additionally, weak and strong consensus
phases scale differently with the system size. The strong consensus phase
exists for superlinear interactions and it is the only consensus phase that
survives in the thermodynamic limit. In the coexistence phase we distinguish a
fully-mixing phase (both states well mixed in the network) and a structured
coexistence phase, where the number of links connecting nodes in different
states (active links) drops significantly due to the formation of two
homogeneous communities of opposite states connected by a few links. The
structured coexistence phase is an example of emergence of community structure
from not exclusively topological dynamics, but coevolution. Our numerical
observations are supported by an analytical description using a pair
approximation approach and an ad-hoc calculation for the transition between the
coexistence and dynamical fragmentation phases. Our work shows how simple
interaction rules including the joint effect of non-linearity, noise, and
coevolution lead to complex structures relevant in the description of social
systems
Opinion dynamics in social networks: From models to data
Opinions are an integral part of how we perceive the world and each other.
They shape collective action, playing a role in democratic processes, the
evolution of norms, and cultural change. For decades, researchers in the social
and natural sciences have tried to describe how shifting individual
perspectives and social exchange lead to archetypal states of public opinion
like consensus and polarization. Here we review some of the many contributions
to the field, focusing both on idealized models of opinion dynamics, and
attempts at validating them with observational data and controlled sociological
experiments. By further closing the gap between models and data, these efforts
may help us understand how to face current challenges that require the
agreement of large groups of people in complex scenarios, such as economic
inequality, climate change, and the ongoing fracture of the sociopolitical
landscape.Comment: 22 pages, 3 figure
Statistical Physics Of Opinion Formation: is it a SPOOF?
We present a short review based on the nonlinear -voter model about
problems and methods raised within statistical physics of opinion formation
(SPOOF). We describe relations between models of opinion formation, developed
by physicists, and theoretical models of social response, known in social
psychology. We draw attention to issues that are interesting for social
psychologists and physicists. We show examples of studies directly inspired by
social psychology like: "independence vs. anticonformity" or "personality vs.
situation". We summarize the results that have been already obtained and point
out what else can be done, also with respect to other models in SPOOF. Finally,
we demonstrate several analytical methods useful in SPOOF, such as the concept
of effective force and potential, Landau's approach to phase transitions, or
mean-field and pair approximations.Comment: 29 pages, 4 figures, new section 6 slightly extended, figures of
higher quality, corrected typos, extended references, other minor
improvements throughout the tex
Vulnerability of democratic electoral systems
The two most common types of electoral systems (ES) used in electing national
legislatures are proportional representation and plurality voting. When they
are evaluated, most often the arguments come from social choice theory and
political sciences. The former overall uses an axiomatic approach including a
list of mathematical criteria a system should fulfill. The latter predominantly
focuses on the trade-off between proportionality of apportionment and
governability. However, there is no consensus on the best ES, nor on the set of
indexes and measures that would be the most important in such assessment.
Moreover, the ongoing debate about the fairness of national elections neglects
the study of their vulnerabilities. Here we address this research gap with a
framework that can measure electoral systems' vulnerability to different means
of influence. Using in silico analysis we show that plurality voting systems
are less stable than proportional representation. They are also more
susceptible to political agitators and media propaganda. A review of real-world
ES reveals possible improvements in their design leading to lower
susceptibility. Additionally, our simulation framework allows computation of
popular indexes, as the Gallagher index or the effective number of parties, in
different scenarios. Our work provides a new tool for dealing with modern
threats to democracy that could destabilize voting processes. Furthermore, our
results add an important argument in a long-standing discussion on evaluation
of ES