72,998 research outputs found
On the role of pre and post-processing in environmental data mining
The quality of discovered knowledge is highly depending on data quality. Unfortunately real data use to contain noise, uncertainty, errors, redundancies or even irrelevant information. The more complex is the reality to be analyzed, the higher the risk of getting low quality data. Knowledge Discovery from Databases (KDD) offers a global framework to prepare data in the right form to perform correct analyses. On the other hand, the quality of decisions taken upon KDD results, depend not only on the quality of the results themselves, but on the capacity of the system to communicate those results in an understandable form. Environmental systems are particularly complex and environmental users particularly require clarity in their results. In this paper some details about how this can be achieved are provided. The role of the pre and post processing in the whole process of Knowledge Discovery in environmental systems is discussed
No entailing laws, but enablement in the evolution of the biosphere
Biological evolution is a complex blend of ever changing structural
stability, variability and emergence of new phenotypes, niches, ecosystems. We
wish to argue that the evolution of life marks the end of a physics world view
of law entailed dynamics. Our considerations depend upon discussing the
variability of the very "contexts of life": the interactions between organisms,
biological niches and ecosystems. These are ever changing, intrinsically
indeterminate and even unprestatable: we do not know ahead of time the "niches"
which constitute the boundary conditions on selection. More generally, by the
mathematical unprestatability of the "phase space" (space of possibilities), no
laws of motion can be formulated for evolution. We call this radical emergence,
from life to life. The purpose of this paper is the integration of variation
and diversity in a sound conceptual frame and situate unpredictability at a
novel theoretical level, that of the very phase space. Our argument will be
carried on in close comparisons with physics and the mathematical constructions
of phase spaces in that discipline. The role of (theoretical) symmetries as
invariant preserving transformations will allow us to understand the nature of
physical phase spaces and to stress the differences required for a sound
biological theoretizing. In this frame, we discuss the novel notion of
"enablement". This will restrict causal analyses to differential cases (a
difference that causes a difference). Mutations or other causal differences
will allow us to stress that "non conservation principles" are at the core of
evolution, in contrast to physical dynamics, largely based on conservation
principles as symmetries. Critical transitions, the main locus of symmetry
changes in physics, will be discussed, and lead to "extended criticality" as a
conceptual frame for a better understanding of the living state of matter
Information, disturbance and Hamiltonian quantum feedback control
We consider separating the problem of designing Hamiltonian quantum feedback
control algorithms into a measurement (estimation) strategy and a feedback
(control) strategy, and consider optimizing desirable properties of each under
the minimal constraint that the available strength of both is limited. This
motivates concepts of information extraction and disturbance which are distinct
from those usually considered in quantum information theory. Using these
concepts we identify an information trade-off in quantum feedback control.Comment: 13 pages, multicol Revtex, 2 eps figure
Entanglement and the Thermodynamic Arrow of Time
We discuss quantum entanglement in the context of the thermodynamic arrow of
time. We review the role of correlations in entropy-decreasing events and prove
that the occurrence of a transformation between two thermodynamic states
constitutes a new type of entanglement witness, one not defined as a separating
plane in state space between separable and entangled states, but as a physical
process dependent on the local initial properties of the states. Extending work
by Partovi, we consider a general entangled multipartite system that allows
large reversals of the thermodynamic arrow of time. We describe a hierarchy of
arrows that arises from the different correlations allowed in a quantum state
and examine these features in the context of Maxwell's Demon. We examine in
detail the case of three qubits, and also propose some simple experimental
demonstrations possible with small numbers of qubits.Comment: 10 pages with 9 figure
More "normal" than normal: scaling distributions and complex systems
One feature of many naturally occurring or engineered complex systems is tremendous variability in event sizes. To account for it, the behavior of these systems is often described using power law relationships or scaling distributions, which tend to be viewed as "exotic" because of their unusual properties (e.g., infinite moments). An alternate view is based on mathematical, statistical, and data-analytic arguments and suggests that scaling distributions should be viewed as "more normal than normal". In support of this latter view that has been advocated by Mandelbrot for the last 40 years, we review in this paper some relevant results from probability theory and illustrate a powerful statistical approach for deciding whether the variability associated with observed event sizes is consistent with an underlying Gaussian-type (finite variance) or scaling-type (infinite variance) distribution. We contrast this approach with traditional model fitting techniques and discuss its implications for future modeling of complex systems
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