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SOCNET  November 2012

SOCNET November 2012

Subject:

Complexity Digest roundup

From:

Dawn Gilpin <[log in to unmask]>

Reply-To:

Dawn Gilpin <[log in to unmask]>

Date:

Thu, 1 Nov 2012 17:26:18 -0700

Content-Type:

text/plain

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Parts/Attachments

text/plain (234 lines)

*****  To join INSNA, visit http://www.insna.org  *****

I don't quite get the method behind the madness of the CD publishing 
schedule, but whatevs. It's only been a couple of days since the last 
update, but this is a really rich issue with something for everyone: 
from financial markets to natural networks, from computational methods 
to philosophies of nonreductionist science, and more. Enjoy!

Dawn


============================
Detecting Causality in Complex Ecosystems

George Sugihara, Robert May, Hao Ye, Chih-hao Hsieh, Ethan Deyle, 
Michael Fogarty, Stephan Munch
Science 26 October 2012:
Vol. 338 no. 6106 pp. 496-500
http://unam.us4.list-manage2.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=9e44b3450a&e=d38efa683e

Identifying causal networks is important for effective policy and 
management recommendations on climate, epidemiology, financial 
regulation, and much else. We introduce a method, based on nonlinear 
state space reconstruction, that can distinguish causality from 
correlation. It extends to nonseparable weakly connected dynamic systems 
(cases not covered by the current Granger causality paradigm). The 
approach is illustrated both by simple models (where, in contrast to the 
real world, we know the underlying equations/relations and so can check 
the validity of our method) and by application to real ecological 
systems, including the controversial sardine-anchovy-temperature problem.

--------------------------------

Spontaneous network formation among cooperative RNA replicators

Nilesh Vaidya, Michael L. Manapat, Irene A. Chen, Ramon Xulvi-Brunet, 
Eric J. Hayden & Niles Lehman
Nature 491, 72–77 (01 November 
2012)http://unam.us4.list-manage.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=1a81d10214&e=d38efa683e

The origins of life on Earth required the establishment of 
self-replicating chemical systems capable of maintaining and evolving 
biological information. In an RNA world, single self-replicating RNAs 
would have faced the extreme challenge of possessing a mutation rate low 
enough both to sustain their own information and to compete successfully 
against molecular parasites with limited evolvability. Thus theoretical 
analyses suggest that networks of interacting molecules were more likely 
to develop and sustain life-like behaviour. Here we show that mixtures 
of RNA fragments that self-assemble into self-replicating ribozymes 
spontaneously form cooperative catalytic cycles and networks. We find 
that a specific three-membered network has highly cooperative growth 
dynamics. When such cooperative networks are competed directly against 
selfish autocatalytic cycles, the former grow faster, indicating an 
intrinsic ability of RNA populations to evolve greater complexity 
through cooperation. We can observe the evolvability of networks through 
in vitro selection. Our experiments highlight the advantages of 
cooperative behaviour even at the molecular stages of nascent life.

--------------------------------
Stability analysis of financial contagion due to overlapping portfolios

Fabio Caccioli, Munik Shrestha, Cristopher Moore, J. Doyne Farmer
http://unam.us4.list-manage1.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=4812414756&e=d38efa683e

Common asset holdings are widely believed to have been the primary 
vector of contagion in the recent financial crisis. We develop a network 
approach to the amplification of financial contagion due to the 
combination of overlapping portfolios and leverage, and we show how it 
can be understood in terms of a generalized branching process. By 
studying a stylized model we estimate the circumstances under which 
systemic instabilities are likely to occur as a function of parameters 
such as leverage, market crowding, diversification, and market impact. 
Although diversification may be good for individual institutions, it can 
create dangerous systemic effects, and as a result financial contagion 
gets worse with too much diversification. Under our model there is a 
critical threshold for leverage; below it financial networks are always 
stable, and above it the unstable region grows as leverage increases. 
The financial system exhibits "robust yet fragile" behavior, with 
regions of theparameter space where contagion is rare but catastrophic 
whenever it occurs. Our model and methods of analysis can be calibrated 
to real data and provide simple yet powerful tools for macroprudential 
stress testing.

--------------------------------
Guaranteeing global synchronization in networks with stochastic interactions

Johannes Klinglmayr et al 2012 New J. Phys. 14 073031
http://unam.us4.list-manage.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=b9f61500d2&e=d38efa683e

We design the interactions between oscillators communicating via 
variably delayed pulse coupling to guarantee their synchronization on 
arbitrary network topologies. We identify a class of response functions 
and prove convergence to network-wide synchrony from arbitrary initial 
conditions. Synchrony is achieved if the pulse emission is unreliable or 
intentionally probabilistic. These results support the design of 
scalable, reliable and energy-efficient communication protocols for 
fully distributed synchronization as needed, e.g., in mobile phone 
networks, embedded systems, sensor networks and autonomously interacting 
swarm robots.

--------------------------------
The Implications of Interactions for Science and Philosophy

Carlos Gershenson
FOUNDATIONS OF SCIENCE
2012, 
http://unam.us4.list-manage2.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=a93505efe9&e=d38efa683e

Reductionism has dominated science and philosophy for centuries. 
Complexity has recently shown that interactions—which reductionism 
neglects—are relevant for understanding phenomena. When interactions are 
considered, reductionism becomes limited in several aspects. In this 
paper, I argue that interactions imply nonreductionism, non-materialism, 
non-predictability, non-Platonism, and non-Nihilism. As alternatives to 
each of these, holism, informism, adaptation, contextuality, and 
meaningfulness are put forward, respectively. A worldview that includes 
interactions not only describes better our world, but can help to solve 
many open scientific, philosophical, and social problems caused by 
implications of reductionism.

--------------------------------
Computing Nature: A Network of Networks of Concurrent Information Processes

Gordana Dodig Crnkovic, Raffaela Giovagnoli
http://unam.us4.list-manage1.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=ff5a422241&e=d38efa683e

This text presents the research field of natural/unconventional 
computing as it appears in the book COMPUTING NATURE. The articles 
discussed consist a selection of works from the Symposium on Natural 
Computing at AISB-IACAP (British Society for the Study of Artificial 
Intelligence and the Simulation of Behaviour and The International 
Association for Computing and Philosophy) World Congress 2012, held at 
the University of Birmingham, celebrating Turing centenary. The 
COMPUTING NATURE is about nature considered as the totality of physical 
existence, the universe. By physical we mean all phenomena, objects and 
processes, that are possible to detect either directly by our senses or 
via instruments. Historically, there have been many ways of describing 
the universe (cosmic egg, cosmic tree, theistic universe, mechanistic 
universe) while a particularly prominent contemporary approach is 
computational universe, as discussed in this article.

--------------------------------

Reconstructing complex networks from time series

Zoran Levnajić
http://unam.us4.list-manage.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=c21bd8a376&e=d38efa683e

Novel method of reconstructing the topology of dynamical networks from 
time series is proposed. By examining the variable--derivative 
correlation of the network node pairs, we derive a simple equation 
yielding the network adjacency matrix. Our key assumption is that the 
intra-network interaction functions are known. We illustrate the method 
on a simple example, and discuss the dependence of the reconstruction on 
the dynamical properties of time series. Our method is applicable to any 
weighted or directed network, in principle allowing for precision to be 
estimated.

--------------------------------
Desynchronizing Networks Using Phase Resetting

J. Borresen, D. Broomhead
http://unam.us4.list-manage.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=66f2aad7b1&e=d38efa683e

Understanding complex systems which exhibit desynchronization as an 
emergent property should have important implications, particularly in 
treating neurological disorders and designing efficient communication 
networks. Here were demonstrate how, using a system similar to the pulse 
coupling used to model firefly interactions, phase desynchronization can 
be achieved in pulse coupled oscillator systems, for a variety of 
network architectures, with symmetric and non symmetric internal 
oscillator frequencies and with both instantaneous and time delayed 
coupling.

--------------------------------
The Emergence of Organizations and Markets

John F. Padgett, Walter W. Powell
Princeton University Press (October 14, 2012)
See it on Scoop.it 
(http://www.scoop.it/t/cxbooks/p/3143277595/the-emergence-of-organizations-and-market) 
, via CxBooks (http://www.scoop.it/t/cxbooks)

The social sciences have sophisticated models of choice and equilibrium 
but little understanding of the emergence of novelty. Where do new 
alternatives, new organizational forms, and new types of people come 
from? Combining biochemical insights about the origin of life with 
innovative and historically oriented social network analyses, John 
Padgett and Walter Powell develop a theory about the emergence of 
organizational, market, and biographical novelty from the coevolution of 
multiple social networks. They demonstrate that novelty arises from 
spillovers across intertwined networks in different domains. In the 
short run actors make relations, but in the long run relations make actors.
This theory of novelty emerging from intersecting production and 
biographical flows is developed through formal deductive modeling and 
through a wide range of original historical case studies. Padgett and 
Powell build on the biochemical concept of autocatalysis--the chemical 
definition of life--and then extend this autocatalytic reasoning to 
social processes of production and communication. Padgett and Powell, 
along with other colleagues, analyze a very wide range of cases of 
emergence. They look at the emergence of organizational novelty in early 
capitalism and state formation; they examine the transformation of 
communism; and they analyze with detailed network data contemporary 
science-based capitalism: the biotechnology industry, regional high-tech 
clusters, and the open source community.

--------------------------------
When Networks Network

See it on Scoop.it 
(http://www.scoop.it/t/papers/p/3143105858/when-networks-network) , via 
Papers (http://www.scoop.it/t/papers)

When networks depend on other networks, such as a communications network 
that relies on a power grid, failure can cascade back and forth between 
the two. This behavior may explain sudden breakdowns in interacting 
systems. Thus, the effects of an attack on a single node can reduce an 
übernetwork that starts with 12 operating nodes to just four.

Once studied solo, systems display surprising behavior when they interact.


______________________________________
Dawn R. Gilpin, PhD
Walter Cronkite School of Journalism & Mass Communication
Arizona State University
[log in to unmask]
@drgilpin

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