868 research outputs found
New foundations for qualitative physics
Physical reality is all the reality we have, and so physical theory in the standard sense
is all the ontology we need. This, at least, was an assumption taken almost
universally for granted by the advocates of exact philosophy for much of the present
century. Every event, it was held, is a physical event, and all structure in reality is
physical structure. The grip of this assumption has perhaps been gradually weakened
in recent years as far as the sciences of mind are concerned. When it comes to the
sciences of external reality, however, it continues to hold sway, so that contemporary
philosophers B even while devoting vast amounts of attention to the language we use
in describing the world of everyday experience B still refuse to see this world as
being itself a proper object of theoretical concern.
Here, however, we shall argue that the usual conception of physical reality as
constituting a unique bedrock of objectivity reflects a rather archaic view as to the
nature of physics itself and is in fact incompatible with the development of the
discipline since Newton. More specifically, we shall seek to show that the world of
qualitative structures, for example of colour and sound, or the commonsense world
of coloured and sounding things, can be treated scientifically (ontologically) on its
own terms, and that such a treatment can help us better to understand the structures both of physical reality and of cognition
Invariant-based approach to symmetry class detection
In this paper, the problem of the identification of the symmetry class of a
given tensor is asked. Contrary to classical approaches which are based on the
spectral properties of the linear operator describing the elasticity, our
setting is based on the invariants of the irreducible tensors appearing in the
harmonic decomposition of the elasticity tensor [Forte-Vianello, 1996]. To that
aim we first introduce a geometrical description of the space of elasticity
tensors. This framework is used to derive invariant-based conditions that
characterize symmetry classes. For low order symmetry classes, such conditions
are given on a triplet of quadratic forms extracted from the harmonic
decomposition of the elasticity tensor , meanwhile for higher-order classes
conditions are provided in terms of elements of , the higher irreducible
space in the decomposition of . Proceeding in such a way some well known
conditions appearing in the Mehrabadi-Cowin theorem for the existence of a
symmetry plane are retrieved, and a set of algebraic relations on polynomial
invariants characterizing the orthotropic, trigonal, tetragonal, transverse
isotropic and cubic symmetry classes are provided. Using a genericity
assumption on the elasticity tensor under study, an algorithm to identify the
symmetry class of a large set of tensors is finally provided.Comment: 32 page
Les Fleurs du mal ou la prosodie du mystère
La plus belle rĂ©ussite de Baudelaire est assurĂ©ment d’avoir rĂ©ussi, dans ses compositions, Ă illustrer cette « prosodie mystĂ©rieuse et mĂ©connue » qu’il trouvait dans la langue française, comme il le rappelait dans son second projet de prĂ©face aux Fleurs du mal. Ă€ cet Ă©gard, son recueil constitue encore aujourd’hui la rĂ©fĂ©rence ad libitum de toute bibliographie poĂ©tique, aussi partielle soit-elle, l’idole cultuelle des Ă©tudiants en lettres, ou l’immarcescible « rĂŞve de pierre » de tout poète en devenir. 
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