4,336 research outputs found
Use of Mutual Coupling to Decrease Parasitic Inductance of Shunt Capacitor Filters
In this paper, we propose and study several new designs of a shunt capacitor filter with two surface-mount technology capacitors. These designs make use of mutual inductance effects to increase the attenuation provided by the filter in the range of high frequencies where the filter behaves inductively. We provide lumped element circuitmodels for the proposed designs that allow identification of the key inductive parameters that determine the high-frequency performance of these filters. We obtain the equa- tions relating these parameters to the effective inductance of the filter, which can be used to compare the high-frequency behavior of different filter designs. We have fabricated and measured several compact shunt capacitor filters with improved performance at high frequencies. We have found that, compared with a shunt capacitor filter with one capacitor, a proper filter design with two capacitors can easily increase in 15–20 dB the high-frequency attenuation provided by the filter. This design also outperforms by 10–15 dB a traditional shunt capacitor filter with two capacitors closely placed. Moreover, this improvement is obtained with no increase in size, cost, or time of design of the filter.Ministerio de EconomÃa Y Competitividad TEC2014-54097-
U-operators
Inspired by a statement of W. Luh asserting the existence of entire functions having together with all their derivatives and antiderivatives
some kind of additive universality or multiplicative universality on certain compact subsets of the complex plane or of, respectively, the punctured complex plane, we introduce in this paper the new concept of U-operators, which are defined on the space of entire functions. Concrete examples, including differential and antidifferential operators, composition, multiplication and shift operators, are studied. A result due to Luh, Martirosian and Müller about the existence of universal entire functions with gap power series is also strengthened.Plan Andaluz de Investigación (Junta de AndalucÃa
Sequences of differential operators: exponentials, hypercyclicity and equicontinuity
In this paper, an eigenvalue criterion for hypercyclicity due to the first author is improved. As a consequence, some new sufficient conditions for a sequence of infinite order linear differential operators to be hypercyclic on the space of holomorphic functions on certain domains of C N are shown. Moreover, several necessary conditions are furnished. The equicontinuity of a family of operators as before is also studied, and it is even characterized if the domain is C N. The results obtained extend or improve earlier work of several authors.Dirección General de Enseñanza Superior (DGES). EspañaJunta de AndalucÃ
Cosmological implications of Primordial Black Holes
The possibility that a relevant fraction of the dark matter might be
comprised of Primordial Black Holes (PBHs) has been seriously reconsidered
after LIGO's detection of a binary black holes merger.
Despite the strong interest in the model, there is a lack of studies on
possible cosmological implications and effects on cosmological parameters
inference. We investigate correlations with the other standard cosmological
parameters using cosmic microwave background observations, finding significant
degeneracies, especially with the tilt of the primordial power spectrum and the
sound horizon at radiation drag. However, these degeneracies can be greatly
reduced with the inclusion of small scale polarization data. We also explore if
PBHs as dark matter in simple extensions of the standard CDM
cosmological model induces extra degeneracies, especially between the
additional parameters and the PBH's ones. Finally, we present cosmic microwave
background constraints on the fraction of dark matter in PBHs, not only for
monochromatic PBH mass distributions but also for popular extended mass
distributions. Our results show that extended mass distribution's constraints
are tighter, but also that a considerable amount of constraining power comes
from the high- polarization data. Moreover, we constrain the shape of
such mass distributions in terms of the correspondent constraints on the PBH
mass fraction.Comment: 20 pages, 9 figures. Matches version accepted to publish in JCA
Towards Accurate Modeling of Line-Intensity Mapping One-Point Statistics: Including Extended Profiles
Line-intensity mapping (LIM) is quickly attracting attention as an
alternative technique to probe large-scale structure and galaxy formation and
evolution at high redshift. LIM one-point statistics are motivated because they
provide access to the highly non-Gaussian information present in line-intensity
maps and contribute to break degeneracies between cosmology and astrophysics.
Now that promising surveys are underway, an accurate model for the LIM
probability distribution function (PDF) is necessary to employ one-point
statistics. We consider the impact of extended emission and limited
experimental resolution in the LIM PDF for the first time. We find that these
effects result in a lower and broader peak at low intensities and a lower tail
towards high intensities. Focusing on the distribution of intensities in the
observed map, we perform the first model validation of LIM one-point statistics
with simulations and find good qualitative agreement. We also discuss the
impact on the covariance, and demonstrate that if not accounted for, large
biases in the astrophysical parameters can be expected in parameter inference.
These effects are also relevant for any summary statistic estimated from the
LIM PDF, and must be implemented to avoid biased results. The comparison with
simulations shows, however, that there are still deviations, mostly related
with the modeling of the clustering of emitters, which encourage further
development of the modeling of LIM one-point statistics.Comment: 13 pages (+3 pages of references), 7 figure
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