2,771 research outputs found
Kolmogorov Complexity, Cosmic Background Radiation and Irreversibility
We discuss the algorithmic information approach to the analysis of the
observational data on the Universe. Kolmogorov complexity is proposed as a
descriptor of the Cosmic Microwave Background (CMB) radiation maps. An
algorithm of computation of the complexity is described, applied, first, to toy
models and then, to the data of the Boomerang experiment. The sky maps obtained
via the summing of two independent Boomerang channels reveal threshold
independent behavior of the mean ellipticity of the anisotropies, thus
indicating correlations present in the sky signal and possibly carrying crucial
information on the curvature and the non-Friedmannian, i.e. accelerated
expansion of the Universe. Similar effect has been detected for COBE-DMR 4 year
maps. Finally, as another application of these concepts, we consider the
possible link between the CMB properties, curvature of the Universe and arrows
of time.Comment: Talk at XXII Solvay Conference on Physics "The Physics of
Communication" (Delphi, November 24-29, 2001); the discussion include
Nature as a Network of Morphological Infocomputational Processes for Cognitive Agents
This paper presents a view of nature as a network of infocomputational agents organized in a dynamical hierarchy of levels. It provides a framework for unification of currently disparate understandings of natural, formal, technical, behavioral and social phenomena based on information as a structure, differences in one system that cause the differences in another system, and computation as its dynamics, i.e. physical process of morphological change in the informational structure. We address some of the frequent misunderstandings regarding the natural/morphological computational models and their relationships to physical systems, especially cognitive systems such as living beings. Natural morphological infocomputation as a conceptual framework necessitates generalization of models of computation beyond the traditional Turing machine model presenting symbol manipulation, and requires agent-based concurrent resource-sensitive models of computation in order to be able to cover the whole range of phenomena from physics to cognition. The central role of agency, particularly material vs. cognitive agency is highlighted
Mathematics Is Biology's Next Microscope, Only Better; Biology Is Mathematics' Next Physics, Only Better
Joel Cohen offers a historical and prospective analysis of the relationship between mathematics and biolog
Report from the MPP Working Group to the NASA Associate Administrator for Space Science and Applications
NASA's Office of Space Science and Applications (OSSA) gave a select group of scientists the opportunity to test and implement their computational algorithms on the Massively Parallel Processor (MPP) located at Goddard Space Flight Center, beginning in late 1985. One year later, the Working Group presented its report, which addressed the following: algorithms, programming languages, architecture, programming environments, the way theory relates, and performance measured. The findings point to a number of demonstrated computational techniques for which the MPP architecture is ideally suited. For example, besides executing much faster on the MPP than on conventional computers, systolic VLSI simulation (where distances are short), lattice simulation, neural network simulation, and image problems were found to be easier to program on the MPP's architecture than on a CYBER 205 or even a VAX. The report also makes technical recommendations covering all aspects of MPP use, and recommendations concerning the future of the MPP and machines based on similar architectures, expansion of the Working Group, and study of the role of future parallel processors for space station, EOS, and the Great Observatories era
Arrows of Time and the Anisotropic Properties of CMB
The relation between the thermodynamical and cosmological arrows of time is
usually viewed in the context of the initial conditions of the Universe. It is
a necessary but not sufficient condition for ensuring the thermodynamical
arrow. We point out that in the Friedmann-Robertson-Walker Universe with
negative curvature, k=-1, there is the second necessary ingredient. It is based
on the geodesic mixing - the dynamical instability of motion along null
geodesics in hyperbolic space. Kolmogorov (algorithmic) complexity as a
universal and experimentally measurable concept can be very useful in
description of this chaotic behavior using the data on Cosmic Microwave
Background radiation. The formulated {\it curvature anthropic principle} states
the negative curvature as a necessary condition for the time asymmetric
Universe with an observer.Comment: Revtex, to appear in the proceedings of the workshop THE CHAOTIC
UNIVERSE, Eds.V.G.Gurzadyan, R.Ruffini, World Sc
NASA scientific and technical publications: A catalog of special publications, reference publications, conference publications, and technical papers, 1989
This catalog lists 190 citations of all NASA Special Publications, NASA Reference Publications, NASA Conference Publications, and NASA Technical Papers that were entered into the NASA scientific and technical information database during accession year 1989. The entries are grouped by subject category. Indexes of subject terms, personal authors, and NASA report numbers are provided
Finding apparent horizons in numerical relativity
This paper presents a detailed discussion of the ``Newton's method'' algorithm for finding apparent horizons in 3+1 numerical relativity. We describe a method for computing the Jacobian matrix of the finite differenced H(h) function \H(\h) by symbolically differentiating the finite difference equations, giving the Jacobian elements directly in terms of the finite difference molecule coefficients used in computing \H(\h). Assuming the finite differencing scheme commutes with linearization, we show how the Jacobian elements may be computed by first linearizing the continuum H(h) equations, then finite differencing the linearized (continuum) equations. We find this symbolic differentiation method of computing the \H(\h) Jacobian to be {\em much\/} more efficient than the usual numerical-perturbation method, and also much easier to implement than is commonly thought. When solving the (discrete) \H(\h) = 0 equations, we find that Newton's method generally converges very rapidly, although there are difficulties when the initial guess contains high-spatial-frequency errors. Using 4th~order finite differencing, we find typical accuracies for the horizon position in the 10^{-5} range for \Delta \theta = \frac{\pi/2}{50}
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