4,638 research outputs found
Information Compression, Intelligence, Computing, and Mathematics
This paper presents evidence for the idea that much of artificial
intelligence, human perception and cognition, mainstream computing, and
mathematics, may be understood as compression of information via the matching
and unification of patterns. This is the basis for the "SP theory of
intelligence", outlined in the paper and fully described elsewhere. Relevant
evidence may be seen: in empirical support for the SP theory; in some
advantages of information compression (IC) in terms of biology and engineering;
in our use of shorthands and ordinary words in language; in how we merge
successive views of any one thing; in visual recognition; in binocular vision;
in visual adaptation; in how we learn lexical and grammatical structures in
language; and in perceptual constancies. IC via the matching and unification of
patterns may be seen in both computing and mathematics: in IC via equations; in
the matching and unification of names; in the reduction or removal of
redundancy from unary numbers; in the workings of Post's Canonical System and
the transition function in the Universal Turing Machine; in the way computers
retrieve information from memory; in systems like Prolog; and in the
query-by-example technique for information retrieval. The chunking-with-codes
technique for IC may be seen in the use of named functions to avoid repetition
of computer code. The schema-plus-correction technique may be seen in functions
with parameters and in the use of classes in object-oriented programming. And
the run-length coding technique may be seen in multiplication, in division, and
in several other devices in mathematics and computing. The SP theory resolves
the apparent paradox of "decompression by compression". And computing and
cognition as IC is compatible with the uses of redundancy in such things as
backup copies to safeguard data and understanding speech in a noisy
environment
Can You hear the Shape of a Market? Geometric Arbitrage and Spectral Theory
Geometric Arbitrage Theory reformulates a generic asset model possibly
allowing for arbitrage by packaging all assets and their forwards dynamics into
a stochastic principal fibre bundle, with a connection whose parallel transport
encodes discounting and portfolio rebalancing, and whose curvature measures, in
this geometric language, the 'instantaneous arbitrage capability' generated by
the market itself. The cashflow bundle is the vector bundle associated to this
stochastic principal fibre bundle for the natural choice of the vector space
fibre. The cashflow bundle carries a stochastic covariant differentiation
induced by the connection on the principal fibre bundle. The link between
arbitrage theory and spectral theory of the connection Laplacian on the vector
bundle is given by the zero eigenspace resulting in a parametrization of all
risk neutral measures equivalent to the statistical one. This indicates that a
market satisfies the (NFLVR) condition if and only if is in the discrete
spectrum of the connection Laplacian on the cash flow bundle or of the Dirac
Laplacian of the twisted cash flow bundle with the exterior algebra bundle. We
apply this result by extending Jarrow-Protter-Shimbo theory of asset bubbles
for complete arbitrage free markets to markets not satisfying the (NFLVR).
Moreover, by means of the Atiyah-Singer index theorem, we prove that the Euler
characteristic of the asset nominal space is a topological obstruction to the
the (NFLVR) condition, and, by means of the Bochner-Weitzenb\"ock formula, the
non vanishing of the homology group of the cash flow bundle is revealed to be a
topological obstruction to (NFLVR), too. Asset bubbles are defined, classified
and decomposed for markets allowing arbitrage.Comment: arXiv admin note: substantial text overlap with arXiv:1406.6805,
arXiv:0910.167
Fractals in the Nervous System: conceptual Implications for Theoretical Neuroscience
This essay is presented with two principal objectives in mind: first, to
document the prevalence of fractals at all levels of the nervous system, giving
credence to the notion of their functional relevance; and second, to draw
attention to the as yet still unresolved issues of the detailed relationships
among power law scaling, self-similarity, and self-organized criticality. As
regards criticality, I will document that it has become a pivotal reference
point in Neurodynamics. Furthermore, I will emphasize the not yet fully
appreciated significance of allometric control processes. For dynamic fractals,
I will assemble reasons for attributing to them the capacity to adapt task
execution to contextual changes across a range of scales. The final Section
consists of general reflections on the implications of the reviewed data, and
identifies what appear to be issues of fundamental importance for future
research in the rapidly evolving topic of this review
Toward the Integration of Economics and Outdoor Recreation Management
The general theme of this bulletin is that improved management of
public-sector recreational resources is a multidisciplinary task. To this
end, we attempt to integrate elements of outdoor recreation management
theory and economics. The bulletin is written for both resource managers
and researchers. For the former, our intent is to emphasize the importance
of being aware of economic implications-at least conceptually-of
management actions that influence the character and availability of recreational
opportunities. To researchers involved in developing recreation
management theory, we draw attention to the parallel between recreation
management theory and the traditional managerial economic model
of the firm. To economists, particularly those involved in developing
and applying nonmarket valuation techniques, we draw attention to the
types of decisions faced by resource managers.
We argue that the most important resource allocation issues are of
the incremental variety, so nonmarket valuation should also yield incremental
values. These values alone, however, are not sufficient
economic input into rational public choice analysis. The missing link ,
or nexus, between outdoor recreation management theory and economic
analysis is the integration of supply and demand, as called for by traditional
managerial economics. Collaborative research to develop recreation
supply response functions akin to agricultural production functions
is an essential step that is missing from both literatures. Theoretical and
applied work assume greater practical importance if they feed information
into this broadened framework. It is our hope that this bulletin will
bring the disciplines closer to that realization
Aggregate Shocks vs Reallocation Shocks: an Appraisal of the Applied Literature
This paper critically appraises the di erent approaches that have characterized the literature on the macroeconomic e ects of job reallocations from Lilien's seminal work to recent developments rooted in structural general equilibrium models, nonlinear econometric techniques and the concepts of job creation and destruction. Despite a ourishing of empirical analysis no unifying theoretical framework has obtained consensus in the scienti c debate. We face a corpus of research which is heterogeneous in variables' selection and experimental design. This widespread heterogeneity makes the evaluation of results a daunting task. Reliability of outcomes becomes almost impossible to assess when, even within models of the same generation, the lack of a rigorous theoretical background hinders well de ned experimental design and makes comparisons di cult. The strong pace at which the empirical literature
on the macroeconomic e ects of job reallocations has been growing in recent years suggests that a general assessment of the state of the art is valuable and maybe indispensable. As a guiding principle for our excursion we track down the methodological development of the proposed solutions to the crucial problem of observational equivalence. We do not linger on speci c econometric methods nor on strictly theoretical issues not relevant to our main purpose. We draw the conclusion that the asymmetric and non-directional nature of allocative shocks, which holds the key to the solution of the problem, is better captured by multivariate, non-linear, dynamic econometric models and numerical simulation techniques. Davis and Haltiwanger's perspective on job creation and destruction seems to us of paramount importance for future research because of its potential to encompass a wealth of micro-level data sets within a rigorous analytical framework.Sectoral shifts, methodology, measurement, assessment
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