269 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
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
On the quantum description of the early universe
Why is it interesting to try to understand the origin of the universe?
Everything we observe today, including our existence, arose from that event.
Although we still do not have a theory that allows us to describe the origin
itself, the study of the very early era of the universe involves the ideal
terrain to analyze the interface between two of today's most successful
physical theories, General Relativity and Quantum physics. But it is also an
area in which we have a large number of observational data to test our
theoretical ideas. Two of the fathers of Quantum physics, Niels Bohr and Werner
Heisenberg, shared some thoughts that could be described with these words:
"Quantum physics tells us that there is a line between the observed and the
observer, and therefore science should be limited to what is observed. We must
give up a complete, objective and realistic theory of the world". This article
will orbit around these ideas and summarizes how it is that today, from recent
works, we are in a position to try to challenge them (at least in part) through
cosmology, seeking the quantum description of the early universe.Comment: 9 page
Novel vacuum conditions in inflationary collapse models
Within the framework of inflationary models that incorporate a spontaneous reduction of the wave function for the emergence of the seeds of cosmic structure, we study the effects on the primordial scalar power spectrum by choosing a novel initial quantum state that characterizes the perturbations of the inflaton. Specifically, we investigate under which conditions one can recover an essentially scale free spectrum of primordial inhomogeneities when the standard Bunch–Davies vacuum is replaced by another one that minimizes the renormalized stress–energy tensor via a Hadamard procedure. We think that this new prescription for selecting the vacuum state is better suited for the self-induced collapse proposal than the traditional one in the semiclassical gravity picture. We show that the parametrization for the time of collapse, considered in previous works, is maintained. Also, we obtain an angular spectrum for the CMB temperature anisotropies consistent with the one that best fits the observational data. Therefore, we conclude that the collapse mechanism might be of a more fundamental character than previously suspected.Facultad de Ciencias Astronómicas y Geofísica
Novel vacuum conditions in inflationary collapse models
Within the framework of inflationary models that incorporate a spontaneous reduction of the wave function for the emergence of the seeds of cosmic structure, we study the effects on the primordial scalar power spectrum by choosing a novel initial quantum state that characterizes the perturbations of the inflaton. Specifically, we investigate under which conditions one can recover an essentially scale free spectrum of primordial inhomogeneities when the standard Bunch–Davies vacuum is replaced by another one that minimizes the renormalized stress–energy tensor via a Hadamard procedure. We think that this new prescription for selecting the vacuum state is better suited for the self-induced collapse proposal than the traditional one in the semiclassical gravity picture. We show that the parametrization for the time of collapse, considered in previous works, is maintained. Also, we obtain an angular spectrum for the CMB temperature anisotropies consistent with the one that best fits the observational data. Therefore, we conclude that the collapse mechanism might be of a more fundamental character than previously suspected.Facultad de Ciencias Astronómicas y Geofísica
Supernova light-curve fitters and Dark Energy
We show that when a procedure is made to remove the tension between a
supernova Ia (SN Ia) data set and observations from BAO and CMB, there might be
the case where the same SN Ia set built with two different light-curve fitters
behaves as two separate and distinct supernova sets, and the tension found by
some authors between supernova sets actually could be due to tension or
inconsistency between fitters. We also show that the information of the fitter
used in an SN Ia data set could be relevant to determine whether phantom type
models are favored or not when such a set is combined with the BAO/CMB joint
parameter.Comment: 8 pages, 7 figures and 2 tables. Improved version. Accepted in Phys.
Lett.
Anisotropic effects of background fields on Born-Infeld electromagnetic waves
We show exact solutions of Born-Infeld theory for electromagnetic plane waves propagating in the presence of static background fields. The non-linear character of Born-Infeld equations generates an interaction between background and wave that changes the speed of propagation and adds a longitudinal component to the wave. As a consequence, in a magnetic background the ray direction differs from the propagation direction --a behavior resembling the one of a wave in an anisotropic medium--. This feature could open up a way to experimental tests of Born-Infeld theory
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