5,487 research outputs found
The Anatomy of a Scientific Rumor
The announcement of the discovery of a Higgs boson-like particle at CERN will
be remembered as one of the milestones of the scientific endeavor of the 21st
century. In this paper we present a study of information spreading processes on
Twitter before, during and after the announcement of the discovery of a new
particle with the features of the elusive Higgs boson on 4th July 2012. We
report evidence for non-trivial spatio-temporal patterns in user activities at
individual and global level, such as tweeting, re-tweeting and replying to
existing tweets. We provide a possible explanation for the observed
time-varying dynamics of user activities during the spreading of this
scientific "rumor". We model the information spreading in the corresponding
network of individuals who posted a tweet related to the Higgs boson discovery.
Finally, we show that we are able to reproduce the global behavior of about
500,000 individuals with remarkable accuracy.Comment: 11 pages, 8 figure
Topological properties of P.A. random graphs with edge-step functions
In this work we investigate a preferential attachment model whose parameter
is a function that drives the asymptotic proportion
between the numbers of vertices and edges of the graph. We investigate
topological features of the graphs, proving general bounds for the diameter and
the clique number. Our results regarding the diameter are sharp when is a
regularly varying function at infinity with strictly negative index of regular
variation . For this particular class, we prove a characterization for
the diameter that depends only on . More specifically, we prove that
the diameter of such graphs is of order with high probability,
although its vertex set order goes to infinity polynomially. Sharp results for
the diameter for a wide class of slowly varying functions are also obtained.
The almost sure convergence for the properly normalized logarithm of the clique
number of the graphs generated by slowly varying functions is also proved
Mesoscopic structure and social aspects of human mobility
The individual movements of large numbers of people are important in many
contexts, from urban planning to disease spreading. Datasets that capture human
mobility are now available and many interesting features have been discovered,
including the ultra-slow spatial growth of individual mobility. However, the
detailed substructures and spatiotemporal flows of mobility - the sets and
sequences of visited locations - have not been well studied. We show that
individual mobility is dominated by small groups of frequently visited,
dynamically close locations, forming primary "habitats" capturing typical daily
activity, along with subsidiary habitats representing additional travel. These
habitats do not correspond to typical contexts such as home or work. The
temporal evolution of mobility within habitats, which constitutes most motion,
is universal across habitats and exhibits scaling patterns both distinct from
all previous observations and unpredicted by current models. The delay to enter
subsidiary habitats is a primary factor in the spatiotemporal growth of human
travel. Interestingly, habitats correlate with non-mobility dynamics such as
communication activity, implying that habitats may influence processes such as
information spreading and revealing new connections between human mobility and
social networks.Comment: 7 pages, 5 figures (main text); 11 pages, 9 figures, 1 table
(supporting information
Hipsters on Networks: How a Small Group of Individuals Can Lead to an Anti-Establishment Majority
The spread of opinions, memes, diseases, and "alternative facts" in a
population depends both on the details of the spreading process and on the
structure of the social and communication networks on which they spread. In
this paper, we explore how \textit{anti-establishment} nodes (e.g.,
\textit{hipsters}) influence the spreading dynamics of two competing products.
We consider a model in which spreading follows a deterministic rule for
updating node states (which describe which product has been adopted) in which
an adjustable fraction of the nodes in a network are hipsters,
who choose to adopt the product that they believe is the less popular of the
two. The remaining nodes are conformists, who choose which product to adopt by
considering which products their immediate neighbors have adopted. We simulate
our model on both synthetic and real networks, and we show that the hipsters
have a major effect on the final fraction of people who adopt each product:
even when only one of the two products exists at the beginning of the
simulations, a very small fraction of hipsters in a network can still cause the
other product to eventually become the more popular one. To account for this
behavior, we construct an approximation for the steady-state adoption fraction
on -regular trees in the limit of few hipsters. Additionally, our
simulations demonstrate that a time delay in the knowledge of the
product distribution in a population, as compared to immediate knowledge of
product adoption among nearest neighbors, can have a large effect on the final
distribution of product adoptions. Our simple model and analysis may help shed
light on the road to success for anti-establishment choices in elections, as
such success can arise rather generically in our model from a small number of
anti-establishment individuals and ordinary processes of social influence on
normal individuals.Comment: Extensively revised, with much new analysis and numerics The abstract
on arXiv is a shortened version of the full abstract because of space limit
Distinguishing Infections on Different Graph Topologies
The history of infections and epidemics holds famous examples where
understanding, containing and ultimately treating an outbreak began with
understanding its mode of spread. Influenza, HIV and most computer viruses,
spread person to person, device to device, through contact networks; Cholera,
Cancer, and seasonal allergies, on the other hand, do not. In this paper we
study two fundamental questions of detection: first, given a snapshot view of a
(perhaps vanishingly small) fraction of those infected, under what conditions
is an epidemic spreading via contact (e.g., Influenza), distinguishable from a
"random illness" operating independently of any contact network (e.g., seasonal
allergies); second, if we do have an epidemic, under what conditions is it
possible to determine which network of interactions is the main cause of the
spread -- the causative network -- without any knowledge of the epidemic, other
than the identity of a minuscule subsample of infected nodes?
The core, therefore, of this paper, is to obtain an understanding of the
diagnostic power of network information. We derive sufficient conditions
networks must satisfy for these problems to be identifiable, and produce
efficient, highly scalable algorithms that solve these problems. We show that
the identifiability condition we give is fairly mild, and in particular, is
satisfied by two common graph topologies: the grid, and the Erdos-Renyi graphs
Complex Contagions in Kleinberg's Small World Model
Complex contagions describe diffusion of behaviors in a social network in
settings where spreading requires the influence by two or more neighbors. In a
-complex contagion, a cluster of nodes are initially infected, and
additional nodes become infected in the next round if they have at least
already infected neighbors. It has been argued that complex contagions better
model behavioral changes such as adoption of new beliefs, fashion trends or
expensive technology innovations. This has motivated rigorous understanding of
spreading of complex contagions in social networks. Despite simple contagions
() that spread fast in all small world graphs, how complex contagions
spread is much less understood. Previous work~\cite{Ghasemiesfeh:2013:CCW}
analyzes complex contagions in Kleinberg's small world
model~\cite{kleinberg00small} where edges are randomly added according to a
spatial distribution (with exponent ) on top of a two dimensional grid
structure. It has been shown in~\cite{Ghasemiesfeh:2013:CCW} that the speed of
complex contagions differs exponentially when compared to when
.
In this paper, we fully characterize the entire parameter space of
except at one point, and provide upper and lower bounds for the speed of
-complex contagions. We study two subtly different variants of Kleinberg's
small world model and show that, with respect to complex contagions, they
behave differently. For each model and each , we show that there is
an intermediate range of values, such that when takes any of these
values, a -complex contagion spreads quickly on the corresponding graph, in
a polylogarithmic number of rounds. However, if is outside this range,
then a -complex contagion requires a polynomial number of rounds to spread
to the entire network.Comment: arXiv admin note: text overlap with arXiv:1404.266
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