819 research outputs found
From Entropic Dynamics to Quantum Theory
Non-relativistic quantum theory is derived from information codified into an
appropriate statistical model. The basic assumption is that there is an
irreducible uncertainty in the location of particles: positions constitute a
configuration space and the corresponding probability distributions constitute
a statistical manifold. The dynamics follows from a principle of inference, the
method of Maximum Entropy. The concept of time is introduced as a convenient
way to keep track of change. A welcome feature is that the entropic dynamics
notion of time incorporates a natural distinction between past and future. The
statistical manifold is assumed to be a dynamical entity: its curved and
evolving geometry determines the evolution of the particles which, in their
turn, react back and determine the evolution of the geometry. Imposing that the
dynamics conserve energy leads to the Schroedinger equation and to a natural
explanation of its linearity, its unitarity, and of the role of complex
numbers. The phase of the wave function is explained as a feature of purely
statistical origin. There is a quantum analogue to the gravitational
equivalence principle.Comment: Extended and corrected version of a paper presented at MaxEnt 2009,
the 29th International Workshop on Bayesian Inference and Maximum Entropy
Methods in Science and Engineering (July 5-10, 2009, Oxford, Mississippi,
USA). In version v3 I corrected a mistake and considerably simplified the
argument. The overall conclusions remain unchange
Jaynes' MaxEnt, Steady State Flow Systems and the Maximum Entropy Production Principle
Jaynes' maximum entropy (MaxEnt) principle was recently used to give a
conditional, local derivation of the ``maximum entropy production'' (MEP)
principle, which states that a flow system with fixed flow(s) or gradient(s)
will converge to a steady state of maximum production of thermodynamic entropy
(R.K. Niven, Phys. Rev. E, in press). The analysis provides a steady state
analog of the MaxEnt formulation of equilibrium thermodynamics, applicable to
many complex flow systems at steady state. The present study examines the
classification of physical systems, with emphasis on the choice of constraints
in MaxEnt. The discussion clarifies the distinction between equilibrium, fluid
flow, source/sink, flow/reactive and other systems, leading into an appraisal
of the application of MaxEnt to steady state flow and reactive systems.Comment: 6 pages; paper for MaxEnt0
Computational methods for Bayesian model choice
In this note, we shortly survey some recent approaches on the approximation
of the Bayes factor used in Bayesian hypothesis testing and in Bayesian model
choice. In particular, we reassess importance sampling, harmonic mean sampling,
and nested sampling from a unified perspective.Comment: 12 pages, 4 figures, submitted to the proceedings of MaxEnt 2009,
July 05-10, 2009, to be published by the American Institute of Physic
Entropic Priors and Bayesian Model Selection
We demonstrate that the principle of maximum relative entropy (ME), used
judiciously, can ease the specification of priors in model selection problems.
The resulting effect is that models that make sharp predictions are
disfavoured, weakening the usual Bayesian "Occam's Razor". This is illustrated
with a simple example involving what Jaynes called a "sure thing" hypothesis.
Jaynes' resolution of the situation involved introducing a large number of
alternative "sure thing" hypotheses that were possible before we observed the
data. However, in more complex situations, it may not be possible to explicitly
enumerate large numbers of alternatives. The entropic priors formalism produces
the desired result without modifying the hypothesis space or requiring explicit
enumeration of alternatives; all that is required is a good model for the prior
predictive distribution for the data. This idea is illustrated with a simple
rigged-lottery example, and we outline how this idea may help to resolve a
recent debate amongst cosmologists: is dark energy a cosmological constant, or
has it evolved with time in some way? And how shall we decide, when the data
are in?Comment: Presented at MaxEnt 2009, the 29th International Workshop on Bayesian
Inference and Maximum Entropy Methods in Science and Engineering (July 5-10,
2009, Oxford, Mississippi, USA
Measuring on Lattices
Previous derivations of the sum and product rules of probability theory
relied on the algebraic properties of Boolean logic. Here they are derived
within a more general framework based on lattice theory. The result is a new
foundation of probability theory that encompasses and generalizes both the Cox
and Kolmogorov formulations. In this picture probability is a bi-valuation
defined on a lattice of statements that quantifies the degree to which one
statement implies another. The sum rule is a constraint equation that ensures
that valuations are assigned so as to not violate associativity of the lattice
join and meet. The product rule is much more interesting in that there are
actually two product rules: one is a constraint equation arises from
associativity of the direct products of lattices, and the other a constraint
equation derived from associativity of changes of context. The generality of
this formalism enables one to derive the traditionally assumed condition of
additivity in measure theory, as well introduce a general notion of product. To
illustrate the generic utility of this novel lattice-theoretic foundation of
measure, the sum and product rules are applied to number theory. Further
application of these concepts to understand the foundation of quantum mechanics
is described in a joint paper in this proceedings.Comment: 13 pages, 7 figures, Presented at the 29th International Workshop on
Bayesian and Maximum Entropy Methods in Science and Engineering: MaxEnt 200
Anti-proliferative effects of raw and steamed extracts of Panax notoginseng and its ginsenoside constituents on human liver cancer cells
10.1186/1749-8546-6-4Chinese Medicine6
Mechanical properties of polyurethane/montmorillonite nanocomposite prepared by melt mixing
Nanocomposites from polyurethane (PU) and montmorillonite (MMT) were prepared under melt-mixing condition, by a twin screw extruder along with a compatibilizer to enhance dispersion of MMT. MMT used in this study was Cloisite 25A (modified with dimethyl hydrogenated tallow 2-ethylhexyl ammonium) or Cloisite 30B (modified with methyl tallow bis-2-hydroxyethyl ammonium). Maleic anhydride grafted polypropylene (MAPP) was used as the compatibilizer. XRD and TEM analysis demonstrated that melt mixing by a twin-screw extruder was effective in dispersing MMT through the PU matrix. The PU/Cloisite 30B composite exhibited better interlayer separation than the PU/Cloiste 25A composite. Nanoparticle dispersion was the best at 1 wt % of MMT and improved with compatibilizer content for both composites. Properties of the composites such as complex viscosity and storage modulus were higher than that of a pure PU matrix and increased with the increase in MMT content, but decreased with the increase in compatibilizer content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56114/1/26721_ftp.pd
An International Collaborative Consensus Statement on En Bloc Resection of Bladder Tumour Incorporating Two Systematic Reviews, a Two-round Delphi Survey and a Consensus Meeting
Funding/Support and role of the sponsor: This study was supported by the General Research Fund/Early Career Scheme of the Research Grants Council, Hong Kong, China (reference no. 24116518).Peer reviewedPostprin
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