4,728 research outputs found
A Fast Frequency Sweep – Green’s Function Based Analysis of Substrate Integrated Waveguide
In this paper, a fast frequency sweep technique is applied to the analysis of Substrate Integrated Waveguides performed with a Green’s function technique. The well-known Asymptotic Waveform Evaluation technique is used to extract the Padè approximation of the frequency response of Substrate Integrated Waveguides devices. The analysis is extended to a large frequency range by adopting the Complex Frequency Hopping algorithm. It is shown that, with this technique, CPU time can be reduced of almost one order of magnitude with respect to a point by point computation
Status of Salerno Laboratory (Measurements in Nuclear Emulsion)
A report on the analysis work in the Salerno Emulsion Laboratory is
presented. It is related to the search for nu_mu->nu_tau oscillations in CHORUS
experiment, the calibrations in the WANF (West Area Neutrino Facility) at Cern
and tests and preparation for new experiments.Comment: Proc. The First International Workshop of Nuclear Emulsion Techniques
(12-24 June 1998, Nagoya, Japan), 15 pages, 11 figure
General Dissipative Materials for Simple Histories
A material with memory typically has a set of many free energy functionals associated with it, all members of which yield the same constitutive relations. An alternative interpretation of this set is explored in the present work. Explicit formulae are derived for the free energy and total dissipation of an arbitrary material in the cases of step function and sinusoidal/exponential histories. Expressions for the fraction of stored and dissipated energy are deduced. Also, various formulae are given for discrete spectrum materials. For materials with relaxation function containing one decaying exponential, the associated Day functional is the physical free energy. For more general materials, we seek a best fit of the relaxation function with one decaying expo- nential to that chosen for the general case. The free energy, total dissipation and fractions of stored and dissipated energies relating to the Day material are derived for the various histories. Similar data, in the case of the general mate- rial, are explored for the minimum and maximum free energies and also for a centrally located free energy given in the literature. Various plots of aspects of this data, including comparisons between the behaviour for general and Day materials, are presented and discussed
Scaling solutions in general non-minimal coupling theories
A class of generalized non-minimal coupling theories is investigated, in
search of scaling attractors able to provide an accelerated expansion at the
present time. Solutions are found in the strong coupling regime and when the
coupling function and the potential verify a simple relation. In such cases,
which include power law and exponential functions, the dynamics is independent
of the exact form of the coupling and the potential. The constraint from the
time variability of , however, limits the fraction of energy in the scalar
field to less than 4% of the total energy density, and excludes accelerated
solutions at the present.Comment: 10 pages, 3 figures, accepted for publication in Phys. Rev.
Cosmological model with interactions in the dark sector
A cosmological model is proposed for the current Universe consisted of
non-interacting baryonic matter and interacting dark components. The dark
energy and dark matter are coupled through their effective barotropic indexes,
which are considered as functions of the ratio between their energy densities.
It is investigated two cases where the ratio is asymptotically stable and their
parameters are adjusted by considering best fits to Hubble function data. It is
shown that the deceleration parameter, the densities parameters, and the
luminosity distance have the correct behavior which is expected for a viable
present scenario of the Universe.Comment: 6 pages, 8 figure
Accretion of non-minimally coupled generalized Chaplygin gas into black holes
The mass evolution of Schwarzschild black holes by the absorption of scalar
fields is investigated in the scenario of the generalized Chaplygin gas (GCG).
The GCG works as a unification picture of dark matter plus dark energy that
naturally accelerates the expansion of the Universe. Through elements of the
quasi-stationary approach, we consider the mass evolution of Schwarzschild
black holes accreted by non-minimally coupled cosmological scalar fields
reproducing the dynamics of the GCG. As a scalar field non-minimally coupled to
the metrics, such an exotic content has been interconnected with accreting
black holes. The black hole increasing masses by the absorption of the gas
reflects some consistence of the accretion mechanism with the hypothesis of the
primordial origin of supermassive black holes. Our results effectively show
that the non-minimal coupling with the GCG dark sector accelerates the
increasing of black hole masses. Meanwhile some exotic features can also be
depicted for specific ranges of the non-minimal coupling in which the GCG
dynamics is substantially modified.Comment: 13 pages, 03 figure
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