1,541 research outputs found
N-flation in Supergravity
We have constructed a large field N-flation model in the supergravity
framework. In this simple set-up, N fields collectively drive inflation where
each field traverses sub-Planckian field values. This has been realised with a
generalisation of the single field chaotic inflation in Supergravity.
Interestingly, despite of the presence of the field interactions, the dynamics
can be described in terms of an effective single field. The observable
predictions of our model i.e. tensor to scalar ratio r and scalar spectral
index n_s are akin to the chaotic inflation.Comment: Minor corrections added, Published Versio
Inflationary Predictions and Moduli Masses
A generic feature of inflationary models in supergravity/string constructions
is vacuum misalignment for the moduli fields. The associated production of
moduli particles leads to an epoch in the post-inflationary history in which
the energy density is dominated by cold moduli particles. This modification of
the post-inflationary history implies that the preferred range for the number
of e-foldings between horizon exit of the modes relevant for CMB observations
and the end of inflation depends on moduli masses. This in turn implies
that the precision CMB observables and are sensitive to moduli
masses. We analyse this sensitivity for some representative models of inflation
and find the effect to be highly relevant for confronting inflationary models
with observations.Comment: 17 pages, 3 figures; v2 minor additions in tex
Gray Image extraction using Fuzzy Logic
Fuzzy systems concern fundamental methodology to represent and process
uncertainty and imprecision in the linguistic information. The fuzzy systems
that use fuzzy rules to represent the domain knowledge of the problem are known
as Fuzzy Rule Base Systems (FRBS). On the other hand image segmentation and
subsequent extraction from a noise-affected background, with the help of
various soft computing methods, are relatively new and quite popular due to
various reasons. These methods include various Artificial Neural Network (ANN)
models (primarily supervised in nature), Genetic Algorithm (GA) based
techniques, intensity histogram based methods etc. providing an extraction
solution working in unsupervised mode happens to be even more interesting
problem. Literature suggests that effort in this respect appears to be quite
rudimentary. In the present article, we propose a fuzzy rule guided novel
technique that is functional devoid of any external intervention during
execution. Experimental results suggest that this approach is an efficient one
in comparison to different other techniques extensively addressed in
literature. In order to justify the supremacy of performance of our proposed
technique in respect of its competitors, we take recourse to effective metrics
like Mean Squared Error (MSE), Mean Absolute Error (MAE), Peak Signal to Noise
Ratio (PSNR).Comment: 8 pages, 5 figures, Fuzzy Rule Base, Image Extraction, Fuzzy
Inference System (FIS), Membership Functions, Membership values,Image coding
and Processing, Soft Computing, Computer Vision Accepted and published in
IEEE. arXiv admin note: text overlap with arXiv:1206.363
N-flation with Hierarchically Light Axions in String Compactifications
We present an explicit embedding of axionic N-flation in type IIB string
compactifications where most of the Kahler moduli are stabilised by
perturbative effects, and so are hierarchically heavier than the corresponding
N >> 1 axions whose collective dynamics drives inflation. This is achieved in
the framework of the LARGE Volume Scenario for moduli stabilisation. Our set-up
can be used to realise a model of either inflation or quintessence, just by
varying the volume of the internal space which controls the scale of the
axionic potential. Both cases predict a very high scale of supersymmetry
breaking. A viable reheating of the Standard Model degrees of freedom can be
achieved after the end of inflation due to the perturbative decay of the N
light axions which drive inflation.Comment: 28 pages, no figures, Journal versio
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