42,085 research outputs found
Reason in Action in Aristotle: A Reading of EE V.12/NE VI.12
I present a reading of EE 5.12/NE 6.12 according to which Aristotle argues for an executive account of φρόνησις (practical wisdom) to show why it is useful to possess this virtue. On this account, the practically wise person's actions are expressive of his knowledge of the fine, a knowledge that only the practically wise person has. This is why he must not only be a good deliberator, but also cunning (δεινότης), able to execute his actions well. An important consequence of this reading is that the debate about whether Aristotle holds a Humean account of practical reason presupposes assumptions about the scope of rationality that Aristotle rejects
An empirical way to correct some drawbacks of mulliken population analysis
Indexación: ScieloThe problem of negative electronic populations and of occupation numbers greater than 2 has plagued Mulliken Population Analysis since the very beginning. Through the analysis of three model molecular systems, several basis sets and the relevant literature, we conclude that there is not enough evidence to assign the origin of these errors to the self-consistent scheme, to Mulliken's partition, to the basis set structure or to a combination of these. As Mulliken Population Analysis is still widely used, we have developed an empirical method to eliminate negative electronic populations and occupation numbers greater than 2. This method can be used for any partition of the electron density (not only Mulliken's), for any basis set and for any LCAO-MO methodology (semiempirical or ab initio). Finally, the method does not produce any change in the original atomic net charges.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072009000400036&lng=es&nrm=is
Practical Knowledge and Luminosity
Many philosophers hold that if an agent acts intentionally, she must know what she is doing. Although the scholarly consensus for many years was to reject the thesis in light of presumed counterexamples by Donald Davidson, several scholars have recently argued that attention to aspectual distinctions and the practical nature of this knowledge shows that these counterexamples fail. In this paper I defend a new objection against the thesis, one modelled after Timothy Williamson’s anti-luminosity argument. Since this argument relies on general principles about the nature of knowledge rather than on intuitions about fringe cases, the recent responses that have been given to defuse the force of Davidson’s objection are silent against it. Moreover, the argument suggests that even weaker theses connecting practical entities with knowledge are also false. Recent defenders of the thesis that there is a necessary connection between knowledge and intentional action are motivated by the insight that this connection is non-accidental. I close with a positive proposal to account for the non-accidentality of this link without appeal to necessary connections by drawing an extended analogy between practical and perceptual knowledge
The optimal momentum map
The presence of symmetries in a Hamiltonian system usually implies the
existence of conservation laws that are represented mathematically in terms of
the dynamical preservation of the level sets of a momentum mapping. The
symplectic or Marsden--Weinstein reduction procedure takes advantage of this
and associates to the original system a new Hamiltonian system with fewer
degrees of freedom. However, in a large number of situations, this standard
approach does not work or is not efficient enough, in the sense that it does
not use all the information encoded in the symmetry of the system. In this
work, a new momentum map will be defined that is capable of overcoming most of
the problems encountered in the traditional approach.Comment: 35 pages. To appear in: Geometry, Dynamics, and Mechanics: 60th
Birthday Volume for J.E. Marsden. P. Holmes, P. Newton, and A. Weinstein,
eds., Springer-Verlag, New York, 200
Perfectly invisible -symmetric zero-gap systems, conformal field theoretical kinks, and exotic nonlinear supersymmetry
We investigate a special class of the -symmetric quantum models
being perfectly invisible zero-gap systems with a unique bound state at the
very edge of continuous spectrum of scattering states. The family includes the
-regularized two particle Calogero systems (conformal quantum
mechanics models of de Alfaro-Fubini-Furlan) and their rational extensions
whose potentials satisfy equations of the KdV hierarchy and exhibit,
particularly, a behaviour typical for extreme waves. We show that the two
simplest Hamiltonians from the Calogero subfamily determine the fluctuation
spectra around the -regularized kinks arising as traveling waves
in the field-theoretical Liouville and conformal Toda systems. Peculiar
properties of the quantum systems are reflected in the associated exotic
nonlinear supersymmetry in the unbroken or partially broken phases. The
conventional supersymmetry is extended here to the
nonlinear supersymmetry that involves two bosonic generators
composed from Lax-Novikov integrals of the subsystems, one of which is the
central charge of the superalgebra. Jordan states are shown to play an
essential role in the construction.Comment: 33 pages; comments and refs added, version to appear in JHE
A symplectic slice theorem
We provide a model for an open invariant neighborhood of any orbit in a
symplectic manifold endowed with a canonical proper symmetry. Our results
generalize the constructions of Marle and Guillemin and Sternberg for canonical
symmetries that have an associated momentum map. In these papers the momentum
map played a crucial role in the construction of the tubular model. The present
work shows that in the construction of the tubular model it can be used the so
called Chu map instead, which exists for any canonical action, unlike the
momentum map. Hamilton's equations for any invariant Hamiltonian function take
on a particularly simple form in these tubular variables. As an application we
will find situations, that we will call tubewise Hamiltonian, in which the
existence of a standard momentum map in invariant neighborhoods is guaranteed.Comment: 14 page
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