125,552 research outputs found
On the complexity and the information content of cosmic structures
The emergence of cosmic structure is commonly considered one of the most
complex phenomena in Nature. However, this complexity has never been defined
nor measured in a quantitative and objective way. In this work we propose a
method to measure the information content of cosmic structure and to quantify
the complexity that emerges from it, based on Information Theory. The emergence
of complex evolutionary patterns is studied with a statistical symbolic
analysis of the datastream produced by state-of-the-art cosmological
simulations of forming galaxy clusters. This powerful approach allows us to
measure how many bits of information are necessary to predict the evolution of
energy fields in a statistical way, and it offers a simple way to quantify
when, where and how the cosmic gas behaves in complex ways. The most complex
behaviors are found in the peripheral regions of galaxy clusters, where
supersonic flows drive shocks and large energy fluctuations over a few tens of
million years. Describing the evolution of magnetic energy requires at least a
twice as large amount of bits than for the other energy fields. When radiative
cooling and feedback from galaxy formation are considered, the cosmic gas is
overall found to double its degree of complexity. In the future, Cosmic
Information Theory can significantly increase our understanding of the
emergence of cosmic structure as it represents an innovative framework to
design and analyze complex simulations of the Universe in a simple, yet
powerful way.Comment: 15 pages, 14 figures. MNRAS accepted, in pres
Brain complexity born out of criticality
In this essay we elaborate on recent evidence demonstrating the presence of a
second order phase transition in human brain dynamics and discuss its
consequences for theoretical approaches to brain function. We review early
evidence of criticality in brain dynamics at different spatial and temporal
scales, and we stress how it was necessary to unify concepts and analysis
techniques across scales to introduce the adequate order and control parameters
which define the transition. A discussion on the relation between structural
vs. dynamical complexity exposes future steps to understand the dynamics of the
connectome (structure) from which emerges the cognitome (function).Comment: In Proceedings of the 12th Granada Seminar "Physics, Computation, and
the Mind - Advances and Challenges at Interfaces-". (J. Marro, P. L. Garrido
& J. J. Torres, Eds.) American Institute of Physics (2012, in press
Testing the structure and process of personality using ambulatory assessment data : an overview of within-person and person-specific techniques
In the present article, we discuss the potential of ambulatory assessment for an idiographic study of the structure and process of personality. To this end, we first review important methodological issues related to the design and implementation of an ambulatory assessment study in the personality domain, including methods of ambulatory assessment, frequency of measurement and duration of the study, ambulatory assessment scales and questionnaires, participant selection, training and motivation, and ambulatory assessment hard- and software. Next, we provide a detailed outline of available analytical approaches that can be used to analyze the intensive longitudinal data generated by an ambulatory assessment study. By doing this, we hope to familiarize personality scholars with these methods and to provide guidance for their use in the field of personality psychology and beyond
Complexity, parallel computation and statistical physics
The intuition that a long history is required for the emergence of complexity
in natural systems is formalized using the notion of depth. The depth of a
system is defined in terms of the number of parallel computational steps needed
to simulate it. Depth provides an objective, irreducible measure of history
applicable to systems of the kind studied in statistical physics. It is argued
that physical complexity cannot occur in the absence of substantial depth and
that depth is a useful proxy for physical complexity. The ideas are illustrated
for a variety of systems in statistical physics.Comment: 21 pages, 7 figure
Dwelling Quietly in the Rich Club: Brain Network Determinants of Slow Cortical Fluctuations
For more than a century, cerebral cartography has been driven by
investigations of structural and morphological properties of the brain across
spatial scales and the temporal/functional phenomena that emerge from these
underlying features. The next era of brain mapping will be driven by studies
that consider both of these components of brain organization simultaneously --
elucidating their interactions and dependencies. Using this guiding principle,
we explored the origin of slowly fluctuating patterns of synchronization within
the topological core of brain regions known as the rich club, implicated in the
regulation of mood and introspection. We find that a constellation of densely
interconnected regions that constitute the rich club (including the anterior
insula, amygdala, and precuneus) play a central role in promoting a stable,
dynamical core of spontaneous activity in the primate cortex. The slow time
scales are well matched to the regulation of internal visceral states,
corresponding to the somatic correlates of mood and anxiety. In contrast, the
topology of the surrounding "feeder" cortical regions show unstable, rapidly
fluctuating dynamics likely crucial for fast perceptual processes. We discuss
these findings in relation to psychiatric disorders and the future of
connectomics.Comment: 35 pages, 6 figure
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