6,377 research outputs found
A New Approach to Equations with Memory
In this work, we present a novel approach to the mathematical analysis of
equations with memory based on the notion of a state, namely, the initial
configuration of the system which can be unambiguously determined by the
knowledge of the future dynamics. As a model, we discuss the abstract version
of an equation arising from linear viscoelasticity. It is worth mentioning that
our approach goes back to the heuristic derivation of the state framework,
devised by L.Deseri, M.Fabrizio and M.J.Golden in "The concept of minimal state
in viscoelasticity: new free energies and applications to PDEs", Arch. Ration.
Mech. Anal., vol. 181 (2006) pp.43-96. Starting from their physical
motivations, we develop a suitable functional formulation which, as far as we
know, is completely new.Comment: 39 pages, no figur
The old anticentre open cluster Berkeley 32: membership and fundamental parameters
We have obtained medium-low resolution spectroscopy and BVI CCD imaging of
Berkeley 32, an old open cluster which lies in the anticentre direction. From
the radial velocities of 48 stars in the cluster direction we found that 31 of
them, in crucial evolutionary phases, are probable cluster members, with an
average radial velocity of +106.7 (sigma = 8.5) km/s. From isochrone fitting to
the colour magnitude diagrams of Berkeley 32 we have obtained an age of 6.3
Gyr, (m-M)0 = 12.48 and E(B-V) = 0.10. The best fit is obtained with Z=0.008. A
consistent distance, (m-M)0 ~= 12.6 +/- 0.1, has been derived from the mean
magnitude of red clump stars with confirmed membership; we may assume (m-M)0 ~=
12.55 +/- 0.1. The colour magnitude diagram of the nearby field observed to
check for field stars contamination looks intriguingly similar to that of the
Canis Major overdensity.Comment: MNRAS, in press. Degraded resolution for Fig.
Possible phases of two coupled n-component fermionic chains
A two-leg ladder with -component fermionic fields in the chains has been
considered using an analytic renormalization group method. The fixed points and
possible phases have been determined for generic filling as well as for a
half-filled system and for the case when one of the subbands is half filled. A
weak-coupling Luttinger-liquid phase and several strong-coupling gapped phases
have been found. In the Luttinger liquid phase, for the most general spin
dependence of the couplings, all modes have different velocities if the
interband scattering processes are scaled out, while doubly degenerate
modes appear if the interband scattering processes remain finite. The role of
backward-scattering, charge-transfer and umklapp processes has been analysed
using their bosonic form and the possible phases are characterized by the
number of gapless modes. As a special case the SU() symmetric Hubbard ladder
has been investigated numerically. It was found that this model does not scale
to the Luttinger liquid fixed point. Even for generic filling gaps open up in
the spectrum of the spin or charge modes, and the system is always insulator in
the presence of umklapp processes
Transport properties of single channel quantum wires with an impurity: Influence of finite length and temperature on average current and noise
The inhomogeneous Tomonaga Luttinger liquid model describing an interacting
quantum wire adiabatically coupled to non-interacting leads is analyzed in the
presence of a weak impurity within the wire. Due to strong electronic
correlations in the wire, the effects of impurity backscattering, finite bias,
finite temperature, and finite length lead to characteristic non-monotonic
parameter dependencies of the average current. We discuss oscillations of the
non-linear current voltage characteristics that arise due to reflections of
plasmon modes at the impurity and quasi Andreev reflections at the contacts,
and show how these oscillations are washed out by decoherence at finite
temperature. Furthermore, the finite frequency current noise is investigated in
detail. We find that the effective charge extracted in the shot noise regime in
the weak backscattering limit decisively depends on the noise frequency
relative to , where is the Fermi velocity, the
Tomonaga Luttinger interaction parameter, and the length of the wire. The
interplay of finite bias, finite temperature, and finite length yields rich
structure in the noise spectrum which crucially depends on the
electron-electron interaction. In particular, the excess noise, defined as the
change of the noise due to the applied voltage, can become negative and is
non-vanishing even for noise frequencies larger than the applied voltage, which
are signatures of correlation effects.Comment: 28 pages, 19 figures, published version with minor change
LA PROTECCIÓN DE LOS DERECHOS INTELECTUALES COMO HERRAMIENTA DE ESTÍMULO PARA LOS SECTORES CIENTÍFICO-TECNOLÓGICOS, NDUSTRIAL Y PARA LA SOCIEDAD
En el presente trabajo, se pondrá de relieve la necesidad de aplicar una herramienta de estímulo poco utilizada por los países en desarrollo: la Protección de la Propiedad Intelectual. Ésta constituye un instrumento válido, que aún no se ha generalizado lo suficiente y que ha mostrado ser útil para incrementar sensiblemente el desarrollo tanto del Sector Científico-Tecnológico, como del Sector Industrial, así como para lograr integrar su actividad con las necesidades e intereses de la Sociedad. Se destaca también la importancia de realizar una búsqueda en bases documentales de patentes antes de emprender un proyecto Científico-Tecnológico, describiendo su mecanismo y los recursos disponibles, y se enfatiza la necesidad proteger el trabajo realizado, a su finalización. Así, la aplicación del derecho de Propiedad Industrial surge como un soporte adecuado para coadyuvar en el proceso de transformación de un logro científico o innovación tecnológica, en una aplicación industrial y en el de su propiedad intelectual que finalmente se tornará en capital intelectual para poder llegar eficazmente a la Sociedad en su conjunto
Assessment of a urban sustainability and life quality index for elderly
The research here presented originates from some of the ongoing challenges of our society: the demographic changes and the high share of population living in urban areas. The aim of the research is the definition of an index of sustainability and quality of life for elderly at suburban scale, not only able to outline aspects related to the local territorial context but also to represent the neighbourhood level. This would provide significant added value to existing indicators that represent the quality of life for much larger areas as cities, regions and nations. Indeed, it is universally recognised that the quality of life varies quite considerably depending on whether you live in different neighbourhoods or urban areas. The index proposed with the research is elaborated on the base of objective and subjective indicators integrated with the judgment of experts, in order to give an accurate and truthful weight to each indicator. Moreover, it has been elaborated for microscale analysis, dividing urban areas into cells, in order to highlight more in detail the real needs of each specific zone. As a result, the elaborated index would be an available tool to be provided to the local public administration to facilitate and optimise the urban planning and management, prioritizing interventions on the base of the sustainability principles and subjective needs of the population, in particular of elderly
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