32,372 research outputs found
Qualitative System Identification from Imperfect Data
Experience in the physical sciences suggests that the only realistic means of
understanding complex systems is through the use of mathematical models.
Typically, this has come to mean the identification of quantitative models
expressed as differential equations. Quantitative modelling works best when the
structure of the model (i.e., the form of the equations) is known; and the
primary concern is one of estimating the values of the parameters in the model.
For complex biological systems, the model-structure is rarely known and the
modeler has to deal with both model-identification and parameter-estimation. In
this paper we are concerned with providing automated assistance to the first of
these problems. Specifically, we examine the identification by machine of the
structural relationships between experimentally observed variables. These
relationship will be expressed in the form of qualitative abstractions of a
quantitative model. Such qualitative models may not only provide clues to the
precise quantitative model, but also assist in understanding the essence of
that model. Our position in this paper is that background knowledge
incorporating system modelling principles can be used to constrain effectively
the set of good qualitative models. Utilising the model-identification
framework provided by Inductive Logic Programming (ILP) we present empirical
support for this position using a series of increasingly complex artificial
datasets. The results are obtained with qualitative and quantitative data
subject to varying amounts of noise and different degrees of sparsity. The
results also point to the presence of a set of qualitative states, which we
term kernel subsets, that may be necessary for a qualitative model-learner to
learn correct models. We demonstrate scalability of the method to biological
system modelling by identification of the glycolysis metabolic pathway from
data
Proof-Pattern Recognition and Lemma Discovery in ACL2
We present a novel technique for combining statistical machine learning for
proof-pattern recognition with symbolic methods for lemma discovery. The
resulting tool, ACL2(ml), gathers proof statistics and uses statistical
pattern-recognition to pre-processes data from libraries, and then suggests
auxiliary lemmas in new proofs by analogy with already seen examples. This
paper presents the implementation of ACL2(ml) alongside theoretical
descriptions of the proof-pattern recognition and lemma discovery methods
involved in it
Historical Aspects of Post-1850 Cosmology
Cosmology as an exact physical science is of new date, but it has long roots
in the past. This essay is concerned with four important themes in the history
of cosmological thought which, if taken together, offer a fairly comprehensive
account of some of the key developments that have led to the modern
understanding of the universe. Apart from the first section, dealing with early
views of curved space, it focuses on mainstream cosmology from the expanding
universe about 1930 to the emergence of the standard big bang model in the
1960s. This development includes theories we would not today consider
"mainstream," such as the steady state model of the universe. The last section
outlines what might be called the prehistory of the concept of dark energy,
that is, ideas that were discussed before dark energy was actually inferred
from supernovae observations in the late 1990s.Comment: 22 pages; Lectures at XVIII Special Courses at Observatorio Nacional,
Rio de Janeiro, Brazil, October 2013. AIP Proceedings (in press
Towards a More Well-Founded Cosmology
First, this paper broaches the definition of science and the epistemic yield
of tenets and approaches: phenomenological (descriptive only), well-founded
(solid first principles, conducive to deep understanding), provisional
(falsifiable if universal, verifiable if existential), and imaginary
(fictitious entities or processes, conducive to empirically unsupported
beliefs). The Big-Bang pardigm and the {\Lambda}CDM "concordance model" involve
such beliefs: the emanation of the universe out of a non-physical stage, cosmic
inflation (invented ad hoc), {\Lambda} (fictitious energy), and exotic dark
matter. They fail in the confidence check that is required in empirical
science. They also face a problem in delimiting what expands from what does
not. In the more well-founded cosmology that emerges, energy is conserved, the
universe is persistent (not transient) and the 'perfect cosmological principle'
holds. Waves and other perturbations that propagate at c (the escape velocity
from the universe) expand exponentially with distance. This dilatation results
from gravitation. The cosmic web of galaxies does not expand. Potential {\Phi}
varies as -H/(cz) instead of -1/r. Inertial forces arise from gravitational
interaction with the rest of the universe (not with space). They are increased
where the universe appears blueshifted and decreased more than proportionately
at very low accelerations. A cut-off acceleration a0 = 0.168 cH is deduced.
This explains the successful description of galaxy rotation curves by MoND. A
fully elaborated physical theory is still pending. The recycling of energy via
a cosmic ocean filled with photons (the CMB), neutrinos and gravitons, and
wider implications for science, are briefly discussed
Introduction to the Neoclassical Interpretation: Quantum Steampunk
In a previous paper we outlined a series of historical touchpoints between classical aether theories and modern theoretical physics which showed a shared conceptual lineage for the modern tools and methods of the most common interpretations and fluid based “Hydrodynamic” treatments of an electromagnetic medium. It was proposed that, though the weight of modern experimentation leaves an extremely narrow and convoluted window for even a reconceptualization of a medium, all of modern physics recognizes a plethora of behaviors and attributes for free space and these physics are interchangeable with modern methods for treating superfluid-like continuums. Thus the mathematical equivalence of the methods do not comprise alternative physics but an alternative interpretation of the same physics. Though many individual components describing a “neo-aether” or “quintessence” are available, an overarching structural outline of how these tools can work together to provide an alternative working overview of modern physics has remained undefined. This paper will propose a set of introductory concepts in the first outline of a toy model which will later connect the alternative tools and conceptualizations with their modern counterparts. This introductory paper provides the simpler “100-miles out” overview of the whole of physics from this perspective, in an easily comprehensible, familiar and intuitive, informal dialog fashion. While this paper grants the largest and loosest introductory overview, subsequent papers in this series will address the finite connections between modern physics and this hydrodynamic view
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