16,378 research outputs found
Gravitational waves in attractors
We study inflation in the attractor model under a non-slow-roll
dynamics with an ansatz proposed by Gong \& Sasaki \cite{Gong:2015ypa} of
assuming . Under this approach, we construct a class of
local shapes of inflaton potential that are different from the T-models. We
find this type of inflationary scenario predicts an attractor at
and . In our approach, the non-slow-roll
inflaton dynamics are related to the parameter which is the curvature
of K\"ahler geometry in the SUGRA embedding of this model.Comment: 6 pages, 2 figures. Contribution to the proceedings of "The
Fourtheenth Marcel Grossmann Meeting on General Relativity", University of
Rome "La Sapienza", Rome, July 12-18, 2015, based on a talk delivered at the
ST4 parallel sessio
Non-slow-roll dynamics in attractors
In this paper we consider the attractor model and study inflation
under a non-slow-roll dynamics. More precisely, we follow the approach recently
proposed by Gong and Sasaki \cite{Gong:2015ypa} by means of assuming
. Within this framework we obtain a family of functions
describing the local shape of the potential during inflation. We study a
specific model and find an inflationary scenario predicting an attractor at
and . We further show that
considering a non-slow-roll dynamics, the attractor model can be
broaden to a wider class of models that remain compatible with value of
. We further explore the model parameter space with respect to large and
small field inflation and conclude that the inflaton dynamics is connected to
the parameter, which is also related to the K\"ahler manifold
curvature in the supergravity (SUGRA) embedding of this model. We also comment
on the stabilization of the inflaton's trajectory.Comment: 17 pages, 6 figures, version accepted in JCA
Inflation in a two 3-form fields scenario
A setting constituted by 3-form fields, without any direct
interaction between them, minimally coupled to gravity, is introduced in this
paper as a framework to study the early evolution of the universe. We focus
particularly on the two 3-forms case. An inflationary scenario is found,
emerging from the coupling to gravity. More concretely, the fields coupled in
this manner exhibit a complex interaction, mediated by the time derivative of
the Hubble parameter. Our investigation is supported by means of a suitable
choice of potentials, employing numerical methods and analytical
approximations. In more detail, the oscillations on the small field limit
become correlated, and one field is intertwined with the other. In this type of
solution, a varying sound speed is present, together with the generation of
isocurvature perturbations. The mentioned features allow to consider an
interesting model, to test against observation. It is subsequently shown how
our results are consistent with current CMB data (viz.Planck and BICEP2).Comment: Version accepted in JCAP. 22 pages, 12 figures, new refs adde
Analyzing Disproportionate Reaction via Comparative Multilingual Targeted Sentiment in Twitter
Global events such as terrorist attacks are commented upon in social media, such as Twitter, in different languages and from different parts of the world. Most prior studies have focused on monolingual sentiment analysis, and therefore excluded an extensive proportion of the Twitter userbase. In this paper, we perform a multilingual comparative sentiment analysis study on the terrorist attack in Paris, during November 2015. In particular, we look at targeted sentiment, investigating opinions on specific entities, not simply the general sentiment of each tweet. Given the potentially inflammatory and polarizing effect that these types of tweets may have on attitudes, we examine the sentiments expressed about different targets and explore whether disproportionate reaction was expressed about such targets across different languages. Specifically, we assess whether the sentiment for French speaking Twitter users during the Paris attack differs from English-speaking ones. We identify disproportionately negative attitudes in the English dataset over the French one towards some entities and, via a crowdsourcing experiment, illustrate that this also extends to forming an annotator bias
DBI Galileon inflation in the light of Planck 2015
In this work we consider a DBI Galileon (DBIG) inflationary model and
constrain its parameter space with the Planck 2015 and BICEP2/Keck array and
Planck (BKP) joint analysis data by means of a potential independent analysis.
We focus our attention on inflationary solutions characterized by a constant or
varying sound speed as well as warp factor. We impose bounds on stringy aspects
of the model, such as the warp factor and the induced gravity
parameter . We study the parameter space of the model
and find that the tensor-to-scalar ratio can be as low as
and inflation happens to be at GUT scale. In addition,
we obtain the tilt of the tensor power spectrum and test the standard
inflationary consistency relation against the latest
bounds from the combined results of BKP+Laser Interferometer
Gravitational-Waves Observatory (LIGO), and find that DBIG inflation predicts a
red spectral index for the tensor power spectrum.Comment: Version accepted in JCAP. 25 pages, 10 figures, new refs adde
Expanding the genetic resources of lentils and Rhizobium to increase nitrogen fixation (BNF) in the lentil crop
Non-Peer Reviewe
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