21,320 research outputs found
Universality of trap models in the ergodic time scale
Consider a sequence of possibly random graphs , ,
whose vertices's have i.i.d. weights with a distribution
belonging to the basin of attraction of an -stable law, .
Let , , be a continuous time simple random walk on which
waits a \emph{mean} exponential time at each vertex . Under
considerably general hypotheses, we prove that in the ergodic time scale this
trap model converges in an appropriate topology to a -process. We apply this
result to a class of graphs which includes the hypercube, the -dimensional
torus, , random -regular graphs and the largest component of
super-critical Erd\"os-R\'enyi random graphs
Irreversible processes and the accelerated-decelerated phases of the Universe
A model for the Universe is proposed where it is considered as a mixture of
scalar and matter fields. The particle production is due to an irreversible
transfer of energy from the gravitational field to the matter field and
represented by a non-equilibrium pressure. This model can simulate three
distinct periods of the Universe: (a) an accelerated epoch where the energy
density of the scalar field prevails over the matter field, (b) a past
decelerated period where the energy density of the matter field becomes more
predominant than the scalar energy density, and (c) a present acceleration
phase where the scalar energy density overcomes the energy density of the
matter field.Comment: 6 pages, 2 figures, to be published in Brazilian Journal of Physic
Lepton masses and mixings in orbifold models with three Higgs families
We analyse the phenomenological viability of heterotic Z(3) orbifolds with
two Wilson lines, which naturally predict three supersymmetric families of
matter and Higgs fields. Given that these models can accommodate realistic
scenarios for the quark sector avoiding potentially dangerous flavour-changing
neutral currents, we now address the leptonic sector, finding that viable
orbifold configurations can in principle be obtained. In particular,it is
possible to accomodate present data on charged lepton masses, while avoiding
conflict with lepton flavour-violating decays. Concerning the generation of
neutrino masses and mixings, we find that Z(3) orbifolds offer several
interesting possibilities.Comment: 28 pages, 11 figures. References adde
Spontaneous CP Violation in the Next-to-Minimal Supersymmetric Standard Model Revisited
We re-examine spontaneous CP violation at the tree level in the context of
the next-to-minimal supersymmetric standard model (NMSSM) with two Higgs
doublets and a gauge singlet field. We analyse the most general Higgs potential
without a discrete Z_3 symmetry, and derive an upper bound on the mass of the
lightest neutral Higgs boson consistent with present experimental data. We
investigate, in particular, its dependence on the admixture and CP-violating
phase of the gauge singlet field, as well as on tan(beta). To assess the
viability of the spontaneous CP violation scenario, we estimate epsilon_K by
applying the mass insertion approximation. We find that a non-trivial flavour
structure in the soft-breaking A terms is required to account for the observed
CP violation in the neutral kaon sector. Furthermore, combining the
minimisation conditions for spontaneous CP violation with the constraints
coming from K0-K0bar mixing, we find that the upper bound on the lightest
Higgs-boson mass becomes stronger. We also point out that the electric dipole
moments of electron and neutron are a serious challenge for SUSY models with
spontaneous CP violation.Comment: 19 pages, LaTeX2e, 5 figures; matches the published versio
Contact angle of a hemispherical bubble: an analytical approach
We have calculated the equilibrium shape of the axially symmetric Plateau border along which a spherical bubble contacts a flat wall, by analytically integrating Laplace’s equation in the presence of gravity, in the limit of small Plateau border sizes. This method has the advantage that it provides closed-form expressions for the positions and orientations of the Plateau border surfaces. Results are in very good overall agreement with those obtained from a numerical solution procedure, and are consistent with
experimental data. In particular we find that the effect of gravity on Plateau border shape is relatively small for typical bubble sizes, leading to a widening of the Plateau border for sessile bubbles and to a narrowing for pendant bubbles. The contact angle of the bubble is found to depend even more weakly on gravity
Densidade de plantas e espaçamento entrelinhas para o híbrido de milho BRS 1002.
bitstream/CNPT-2010/39573/1/Circular-68.pd
Densidade de plantas e espaçamento entrelinhas para o híbrido de milho BRS 1002.
bitstream/item/30861/1/Circular-68.pd
The innovative behaviour of tourism firms
Tourism is a growing and an extremely competitive sector. To be competitive, tourism firms need do innovate, responding to the more and more demanding tourist. Nonetheless, research on this field is limited and insufficient. In Portugal, the tourism sector is a highly strategic sector for the Portuguese economy, but there is no evidence on how Portuguese tourism firms innovate. This paper presents a thesis proposal with the aim to provide empirical evidence of the innovative behaviour of Portuguese tourism firm. Trough a direct survey on all the Portuguese tourism firms we intent to investigate firms’ innovativeness and their determinants and then compare the results with data from Danish and Spanish tourism firms. The literature on innovation in services and in tourism, in particular Sunbdo et al. (2007) taxonomy of tourism firms, provides us a guide to our investigation. It is also our aim to contribute with additional findings on the process of innovation in the tourism industry.Innovation, Tourism Industries, Portugal
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