639 research outputs found

    Topological mass mechanism and exact fields mapping

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    We present a class of mappings between models with topological mass mechanism and purely topological models in arbitrary dimensions. These mappings are established by directly mapping the fields of one model in terms of the fields of the other model in closed expressions. These expressions provide the mappings of their actions as well as the mappings of their propagators. For a general class of models in which the topological model becomes the BF model the mappings present arbitrary functions which otherwise are absent for Chern-Simons like actions. This work generalizes the results of [1] for arbitrary dimensions.Comment: 11 page

    A new picture on (3+1)D topological mass mechanism

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    We present a class of mappings between the fields of the Cremmer-Sherk and pure BF models in 4D. These mappings are established by two distinct procedures. First a mapping of their actions is produced iteratively resulting in an expansion of the fields of one model in terms of progressively higher derivatives of the other model fields. Secondly an exact mapping is introduced by mapping their quantum correlation functions. The equivalence of both procedures is shown by resorting to the invariance under field scale transformations of the topological action. Related equivalences in 5D and 3D are discussed. A cohomological argument is presented to provide consistency of the iterative mapping.Comment: 13 page

    Facts, Norms and Expected Utility Functions

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    International audienceIn this paper we want to explore an argumentative pattern that provides a normative justification for expected utility functions grounded on empirical evidence, showing how it worked in three different episodes of their development. The argument claims that we should prudentially maximize our expected utility since this is the criterion effectively applied by those who are considered wisest in making risky choices (be it gamblers or businessmen). Yet, to justify the adoption of this rule, it should be proven that this is empirically true: i.e., that a given function allows us to predict the choices of that particular class of agents. We show how expected utility functions were introduced and contested in accordance to this pattern in the 18th century and how it recurred in the 1950s when M. Allais made his case against the neobernoullians

    Randomised controlled trial of video clips and interactive games to improve vision in children with amblyopia using the I-BiT system

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    Background Traditional treatment of amblyopia involves either wearing a patch or atropine penalisation of the better eye. A new treatment is being developed on the basis of virtual reality technology allowing either DVD footage or computer games which present a common background to both eyes and the foreground, containing the imagery of interest, only to the amblyopic eye. Methods A randomised control trial was performed on patients with amblyopia aged 4–8 years with three arms. All three arms had dichoptic stimulation using shutter glass technology. One arm had DVD footage shown to the amblyopic eye and common background to both, the second used a modified shooter game, Nux, with sprite and targets presented to the amblyopic eye (and background to both) while the third arm had both background and foreground presented to both eyes (non-interactive binocular treatment (non-I-BiT) games). Results Seventy-five patients were randomised; 67 were residual amblyopes and 70 had an associated strabismus. The visual acuity improved in all three arms by approximately 0.07 logMAR in the amblyopic eye at 6 weeks. There was no difference between I-BiT DVD and non-I-BiT games compared with I-BiT games (stated primary outcome) in terms of gain in vision. Conclusions There was a modest vision improvement in all three arms. Treatment was well tolerated and safe. There was no difference between the three treatments in terms of primary stated outcomes but treatment duration was short and the high proportion of previously treated amblyopia and strabismic amblyopia disadvantaged dichoptic stimulation treatment

    An Italian foreign policy of religious engagement: challenges and prospects

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    A new awareness of the role of religion in international relations has started to inform concrete policy discussions in several Western Ministries of Foreign Affairs under the heading of ‘religious engagement’ in foreign policy. Italy is no exception, but as the country which hosts the Holy See, it represents a special case. As the approach to religion found in the historical record of Italian foreign policy shows, Italy has a comparative advantage and could well develop a unique model of religious engagement by strengthening the central structures involved in religious matters and foreign policy, as well as by using the vast network of Rome-based religious non-state actors as a forum of consultation and policy advice

    A candidate for a background independent formulation of M theory

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    A class of background independent membrane field theories are studied, and several properties are discovered which suggest that they may play a role in a background independent form of M theory. The bulk kinematics of these theories are described in terms of the conformal blocks of an algebra G on all oriented, finite genus, two-surfaces. The bulk dynamics is described in terms of causal histories in which time evolution is specified by giving amplitudes to certain local changes of the states. Holographic observables are defined which live in finite dimensional states spaces associated with boundaries in spacetime. We show here that the natural observables in these boundary state spaces are, when G is chosen to be Spin(D) or a supersymmetric extension of it, generalizations of matrix model coordinates in D dimensions. In certain cases the bulk dynamics can be chosen so the matrix model dynamics is recoverd for the boundary observables. The bosonic and supersymmetric cases in D=3 and D=9 are studied, and it is shown that the latter is, in a certain limit, related to the matrix model formulation of M theory. This correspondence gives rise to a conjecture concerning a background independent form of M theory in terms of which excitations of the background independent membrane field theory that correspond to strings and D0 branes are identified.Comment: Latex 46 pages, 21 figures, new results included which lead to a modification of the statement of the basic conjecture. Presentation improve

    Kant, race, and natural history

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    This article presents a new argument concerning the relation between Kant’s theory of race and aspects of the critical philosophy. It argues that Kant’s treatment of the problem of the systematic unity of nature and knowledge in the Critique of Pure Reason and the Critique of the Power of Judgment can be traced back a methodological problem in the natural history of the period – that of the possibility of a natural system of nature. Kant’s transformation of the methodological problem from natural history into a set of philosophical (and specifically epistemological) problems proceeds by way of the working out of his own problem in natural history – the problem of the natural history of the human races – and specifically the problem of the unity in diversity of the human species, in response to which he develops a theory of race. This theory of race is, further, the first developed model of the use of teleological judgment in Kant’s work. The article thus argues that Kant’s philosophical position on the systematic unity of nature and of knowledge in the first and third Critiques, and his account and defense of teleological judgment, are developed out of problems first articulated in his solution to the problem of the unity in diversity of the human species – that is, in his theory of race. The article does not seek to establish that these aspects of the critical philosophy are therefore racialised. But it does demonstrate, against those who deny its salience to his philosophy, how the problem of the unity in diversity of the human species and Kant’s theory of race is significant for the development of aspects of the critical philosophy and thus contributes to their philosophical problematics
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