1,519 research outputs found
Synchrotron Emissions in GRB Prompt Phase Using a Semi Leptonic and Hadronic Model
In this communication devoted to the prompt emission of GRBs, we claim that
some important parameters associated to the magnetic field, such as its index
profile, the index of its turbulence spectrum and its level of irregularities,
will be measurable with GLAST. In particular the law relating the peak energy
Epeak with the total energy E (like Amati's law) constrains the turbulence
spectrum index and, among all existing theories of MHD turbulence, is
compatible with the Kolmogorov scaling only. Thus, these data will allow a much
better determination of the performances of GRBs as particle accelerators. This
opens the possibility to characterize both electron and proton acceleration
more seriously. We discuss the possible generation of UHECRs and of its
signature through GeV-TeV synchrotron emission.Comment: 30th International Cosmic Ray Conference (ICRC2007) - Proceeding
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Ephemeral properties and the illusion of microscopic particles
Founding our analysis on the Geneva-Brussels approach to quantum mechanics,
we use conventional macroscopic objects as guiding examples to clarify the
content of two important results of the beginning of twentieth century:
Einstein-Podolsky-Rosen's reality criterion and Heisenberg's uncertainty
principle. We then use them in combination to show that our widespread belief
in the existence of microscopic particles is only the result of a cognitive
illusion, as microscopic particles are not particles, but are instead the
ephemeral spatial and local manifestations of non-spatial and non-local
entities
Dossier Mobilités spatiales et ressources métropolitaines : l'accessibilité en questions
Cet article, avant tout méthodologique, explore la dispersion spatiale des lieux d'activité (étude et travail) fréquentés au quotidien par des individus au regard de leurs caractéristiques sociodémographiques et de leur lieu de résidence, dans l'agglomération de São Paulo. L'étude repose sur l'exploitation de données d'enquêtes sur les systèmes de mobilités réalisées auprès d'un échantillon de ménages. L'accent est mis sur la démarche qui fait intervenir une série d'analyses centrographiques que l'on combine dans un deuxième temps à une analyse typologique. Nous montrons l'intérêt de recourir à ces outils pour appréhender et visualiser les inégalités d'accès aux ressources urbaines en lien avec le cycle de vie des individus, la hiérarchie sociale et le lieu de résidence
Formal concept analysis and structures underlying quantum logics
A Hilbert space induces a formal context, the Hilbert formal context , whose associated concept lattice is isomorphic to the lattice of closed subspaces of . This set of closed subspaces, denoted , is important in the development of quantum logic and, as an algebraic structure, corresponds to a so-called ``propositional system'', that is, a complete, atomistic, orthomodular lattice which satisfies the covering law.
In this paper, we continue with our study of the Chu construction by introducing the Chu correspondences between Hilbert contexts, and showing that the category of Propositional Systems, PropSys, is equivalent to the category of of Chu correspondences between Hilbert contextsUniversidad de Málaga. Campus de Excelencia Internacional AndalucÃa Tech
The role of infrared divergence for decoherence
Continuous and discrete superselection rules induced by the interaction with
the environment are investigated for a class of exactly soluble Hamiltonian
models. The environment is given by a Boson field. Stable superselection
sectors emerge if and only if the low frequences dominate and the ground state
of the Boson field disappears due to infrared divergence. The models allow
uniform estimates of all transition matrix elements between different
superselection sectors.Comment: 11 pages, extended and simplified proo
Measurement Theory in Lax-Phillips Formalism
It is shown that the application of Lax-Phillips scattering theory to quantum
mechanics provides a natural framework for the realization of the ideas of the
Many-Hilbert-Space theory of Machida and Namiki to describe the development of
decoherence in the process of measurement. We show that if the quantum
mechanical evolution is pointwise in time, then decoherence occurs only if the
Hamiltonian is time-dependent. If the evolution is not pointwise in time (as in
Liouville space), then the decoherence may occur even for closed systems. These
conclusions apply as well to the general problem of mixing of states.Comment: 14 pages, IASSNS-HEP 93/6
Schwinger Algebra for Quaternionic Quantum Mechanics
It is shown that the measurement algebra of Schwinger, a characterization of
the properties of Pauli measurements of the first and second kinds, forming the
foundation of his formulation of quantum mechanics over the complex field, has
a quaternionic generalization. In this quaternionic measurement algebra some of
the notions of quaternionic quantum mechanics are clarified. The conditions
imposed on the form of the corresponding quantum field theory are studied, and
the quantum fields are constructed. It is shown that the resulting quantum
fields coincide with the fermion or boson annihilation-creation operators
obtained by Razon and Horwitz in the limit in which the number of particles in
physical states .Comment: 20 pages, Plain Te
Optically tailored access to metastable electronic states
On irradiating a molecular system with a laser beam of ultraviolet or visible frequency, photon absorption occurs when an electronic state is at a suitable energy level relative to an initial state. Despite meeting this criterion, interesting metastable states can remain inaccessible because of symmetry constraints. In this Letter a mechanism, based on the input of an off-resonant beam, is shown to enable the population of such states. This is achievable because the laser-modified process involves different selection rules compared to conventional photon absorption. The effects of applying the stimulus beam to either a one- or two-photon process are examined
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