1,678 research outputs found
Nonequilibrium phase transition in the coevolution of networks and opinions
Models of the convergence of opinion in social systems have been the subject
of a considerable amount of recent attention in the physics literature. These
models divide into two classes, those in which individuals form their beliefs
based on the opinions of their neighbors in a social network of personal
acquaintances, and those in which, conversely, network connections form between
individuals of similar beliefs. While both of these processes can give rise to
realistic levels of agreement between acquaintances, practical experience
suggests that opinion formation in the real world is not a result of one
process or the other, but a combination of the two. Here we present a simple
model of this combination, with a single parameter controlling the balance of
the two processes. We find that the model undergoes a continuous phase
transition as this parameter is varied, from a regime in which opinions are
arbitrarily diverse to one in which most individuals hold the same opinion. We
characterize the static and dynamical properties of this transition
Relativistic Images in Randall-Sundrum II Braneworld Lensing
In this paper, we explore the properties of gravitational lensing by black
holes in the Randall-Sundrum II braneworld. We use numerical techniques to
calculate lensing observables using the Tidal Reissner-Nordstrom (TRN) and
Garriga-Tanaka metrics to examine supermassive black holes and primordial black
holes. We introduce a new way tp parameterize tidal charge in the TRN metric
which results in a large increase in image magnifications for braneworld
primordial black holes compared to their 4 dimensional analogues. Finally, we
offer a mathematical analysis that allows us to analyze the validity of the
logarithmic approximation of the bending angle for any static, spherically
symmetric metric. We apply this to the TRN metric and show that it is valid for
any amount of tidal charge.Comment: 13 pages, 3 figures; Accepted for Publication in Physical Review
Neutral theory of chemical reaction networks
To what extent do the characteristic features of a chemical reaction network
reflect its purpose and function? In general, one argues that correlations
between specific features and specific functions are key to understanding a
complex structure. However, specific features may sometimes be neutral and
uncorrelated with any system-specific purpose, function or causal chain. Such
neutral features are caused by chance and randomness. Here we compare two
classes of chemical networks: one that has been subjected to biological
evolution (the chemical reaction network of metabolism in living cells) and one
that has not (the atmospheric planetary chemical reaction networks). Their
degree distributions are shown to share the very same neutral
system-independent features. The shape of the broad distributions is to a large
extent controlled by a single parameter, the network size. From this
perspective, there is little difference between atmospheric and metabolic
networks; they are just different sizes of the same random assembling network.
In other words, the shape of the degree distribution is a neutral
characteristic feature and has no functional or evolutionary implications in
itself; it is not a matter of life and death.Comment: 13 pages, 8 figure
A generalization of the Heine--Stieltjes theorem
We extend the Heine-Stieltjes Theorem to concern all (non-degenerate)
differential operators preserving the property of having only real zeros. This
solves a conjecture of B. Shapiro. The new methods developed are used to
describe intricate interlacing relations between the zeros of different pairs
of solutions. This extends recent results of Bourget, McMillen and Vargas for
the Heun equation and answers their question on how to generalize their results
to higher degrees. Many of the results are new even for the classical case.Comment: 12 pages, typos corrected and refined the interlacing theorem
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