54,056 research outputs found
Quantum propagator for some classes of three-dimensional three-body systems
In this work we solve exactly a class of three-body propagators for the most
general quadratic interactions in the coordinates, for arbitrary masses and
couplings. This is done both for the constant as the time-dependent couplings
and masses, by using the Feynman path integral formalism. Finally the energy
spectrum and the eigenfunctions are recovered from the propagators.Comment: 16 pages, no figure
Gain and noise spectral density in an electronic parametric amplifier with added white noise
In this paper, we discuss the behavior of a linear classical parametric
amplifier (PA) in the presence of white noise and give theoretical estimates of
the noise spectral density based on approximate Green's functions obtained by
using averaging techniques. Furthermore, we give analytical estimates for
parametric amplification bandwidth of the amplifier and for the noisy
precursors to instability. To validate our theory we compare the analytical
results with experimental data obtained in an analog circuit. We describe the
implementation details and the setup used in the experimental study of the
amplifier. Near the threshold to the first parametric instability, and in
degenerate-mode amplification, the PA achieved very high gains in a very narrow
bandwidth centered on its resonance frequency. In quasi-degenerate mode
amplification, we obtained lower values of gain, but with a wider bandwidth
that is tunable. The experimental data were accurately described by the
predictions of the model. Moreover, we noticed spectral components in the
output signal of the amplifier which are due to noise precursors of
instability. The position, width, and magnitude of these components are in
agreement with the noise spectral density obtained by the theory proposed here
Orbit based procedure for doublets of scalar fields and the emergence of triple kinks and other defects
In this work we offer an approach to enlarge the number of exactly solvable
models with two real scalar fields in (1+1)D. We build some new two-field
models, and obtain their exact orbits and exact or numerical field
configurations. It is noteworthy that a model presenting triple-kinks and
double-flat-top lumps is among those new models
The Dyer-Roeder relation in a universe with particle production
We have obtained analytical exact solutions of the Dyer-Roeder equation in a
cosmological model where creation of particles occurs at the expenses of the
gravitational field. We discussed the influences of inhomogeneities in the path
of a light beam on the apparent diameter of astrophysical objects and consider
both redshift independent as redshift dependent distributions of the
inhomogeneities.Comment: 7 pages, 4 figures. Accepted to be published in the Astronomy and
Astrophysics Journa
Coupled scalar fields Oscillons and Breathers in some Lorentz Violating Scenarios
In this work we discuss the impact of the breaking of the Lorentz symmetry on
the usual oscillons, the so-called flat-top oscillons, and the breathers. Our
analysis is performed by using a Lorentz violation scenario rigorously derived
in the literature. We show that the Lorentz violation is responsible for the
origin of a kind of deformation of the configuration, where the field
configuration becomes oscillatory in a localized region near its maximum value.
Furthermore, we show that the Lorentz breaking symmetry produces a displacement
of the oscillon along the spatial direction, the same feature is present in the
case of breathers. We also show that the effect of a Lorentz violation in the
flat-top oscillon solution is responsible by the shrinking of the flat-top.
Furthermore, we find analytically the outgoing radiation, this result indicates
that the amplitude of the outgoing radiation is controlled by the Lorentz
breaking parameter, in such away that this oscillon becomes more unstable than
its symmetric counterpart, however, it still has a long living nature
On the study of oscillons in scalar field theories: A new approach
In this work we study configurations in one-dimensional scalar field theory,
which are time-dependent, localized in space and extremely long-lived called
oscillons. It is investigated how the action of changing the minimum value of
the field configuration representing the oscillon affects its behavior. We find
that one of the consequences of this procedure, is the appearance of a pair of
oscillon-like structures presenting different amplitudes and frequencies of
oscillation. We also compare our analytical results to numerical ones, showing
excellent agreement
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