265,200 research outputs found
Emergence of inflationary perturbations in the CSL model
The inflationary paradigm is the most successful model that explains the
observed spectrum of primordial perturbations. However, the precise emergence
of such inhomogeneities and the quantum-to-classical transition of the
perturbations has not yet reached a consensus among the community. The
Continuous Spontaneous Localization model (CSL), in the cosmological context,
might be used to provide a solution to the mentioned issues by considering a
dynamical reduction of the wave function. The CSL model has been applied to the
inflationary universe before and different conclusions have been obtained. In
this letter, we use a different approach to implement the CSL model during
inflation. In particular, in addition to accounting for the
quantum-to-classical transition, we use the CSL model to generate the
primordial perturbations, that is, the dynamical evolution provided by the CSL
model is responsible for the transition from a homogeneous and isotropic
initial state to a final one lacking such symmetries. Our approach leads to
results that can be clearly distinguished from preceding works. Specifically,
the scalar and tensor power spectra are not time-dependent, and retains the
amplification mechanism of the CSL model. Moreover, our framework depends only
on one parameter (the CSL parameter) and its value is consistent with
cosmological and laboratory observations.Comment: 14 pages. Final version. To be published in EPJ
A Perl Package and an Alignment Tool for Phylogenetic Networks
Phylogenetic networks are a generalization of phylogenetic trees that allow
for the representation of evolutionary events acting at the population level,
like recombination between genes, hybridization between lineages, and lateral
gene transfer. While most phylogenetics tools implement a wide range of
algorithms on phylogenetic trees, there exist only a few applications to work
with phylogenetic networks, and there are no open-source libraries either.
In order to improve this situation, we have developed a Perl package that
relies on the BioPerl bundle and implements many algorithms on phylogenetic
networks. We have also developed a Java applet that makes use of the
aforementioned Perl package and allows the user to make simple experiments with
phylogenetic networks without having to develop a program or Perl script by
herself.
The Perl package has been accepted as part of the BioPerl bundle. It can be
downloaded from http://dmi.uib.es/~gcardona/BioInfo/Bio-PhyloNetwork.tgz. The
web-based application is available at http://dmi.uib.es/~gcardona/BioInfo/. The
Perl package includes full documentation of all its features.Comment: 5 page
Quasi-matter bounce and inflation in the light of the CSL model
The Continuous Spontaneous Localization (CSL) model has been proposed as a
possible solution to the quantum measurement problem by modifying the
Schr\"{o}dinger equation. In this work, we apply the CSL model to two
cosmological models of the early Universe: the matter bounce scenario and slow
roll inflation. In particular, we focus on the generation of the classical
primordial inhomogeneities and anisotropies that arise from the dynamical
evolution, provided by the CSL mechanism, of the quantum state associated to
the quantum fields. In each case, we obtained a prediction for the shape and
the parameters characterizing the primordial spectra (scalar and tensor), i.e.
the amplitude, the spectral index and the tensor-to-scalar ratio. We found that
there exist CSL parameter values, allowed by other non-cosmological
experiments, for which our predictions for the angular power spectrum of the
CMB temperature anisotropy are consistent with the best fit canonical model to
the latest data released by the Planck Collaboration.Comment: 27 pages, including 6 figures, 2 tables and one Appendix. Final
version. Accepted in EPJ
Fundamental Radar Properties: Hidden Variables in Spacetime
A derivation of the properties of pulsed radiative imaging systems is
presented with examples drawn from conventional, synthetic aperture, and
interferometric radar. A geometric construction of the space and time
components of a radar observation yields a simple underlying structural
equivalence between many of the properties of radar, including resolution,
range ambiguity, azimuth aliasing, signal strength, speckle, layover, Doppler
shifts, obliquity and slant range resolution, finite antenna size, atmospheric
delays, and beam and pulse limited configurations. The same simple structure is
shown to account for many interferometric properties of radar - height
resolution, image decorrelation, surface velocity detection, and surface
deformation measurement. What emerges is a simple, unified description of the
complex phenomena of radar observations. The formulation comes from fundamental
physical concepts in relativistic field theory, of which the essential elements
are presented. In the terminology of physics, radar properties are projections
of hidden variables - curved worldlines from a broken symmetry in Minkowski
spacetime - onto a time-serial receiver.Comment: 24 pages, 18 figures Accepted JOSA-
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