453 research outputs found
Gauge-flation Vs Chromo-Natural Inflation
Gauge-flation, non-Abelian gauge field inflation, which was introduced in
arXiv:1102.1513 and analyzed more thoroughly in arXiv:1102.1932, is a model of
inflation driven by non-Abelian gauge fields minimally coupled to Einstein
gravity. In this model certain rotationally invariant combination of gauge
fields play the role of inflaton. Recently, the chromo-natural inflation model
was proposed arXiv:1202.2366 which besides the non-Abelian gauge fields also
involve an axion field. In this short note we show that the model involving
axions, indeed allows for various slow-roll trajectories for different values
of its parameters: A specific trajectory discussed in arXiv:1202.2366 starts
from a "small axion" region, while the trajectory considered in arXiv:1102.1513
corresponds to a "large axion" region.Comment: 4 page, no figure
A new perspective on Gauge-flation
Recently Maleknejad and Sheikh-Jabbari have proposed a new model for
inflation with non-Abelian gauge fields (Gauge-flation), and they have studied
the model by numerical methods\cite{Sheikh}. In this model, the isotropy of
space-time is recovered by suitable combination of gauge configurations, and a
scalar field is constructed by gauge field and the scale factor, which produces
inflation period. In this work, exact solutions for the scalar field and the
Hubble parameter are presented and we provide analytic solutions for the
numerical results. We explicitly present Hubble parameter and fields as
functions of time and it is also demonstrated that in some conditions they are
damped oscillator. Moreover, reheating period in the model is discussed.Comment: 7 pages, 6 figures,3 figures and a section added, improved discussio
Production and Backreaction of Fermions from Axion- Gauge Fields during Inflation
gauge fields and axions can have a stable, isotropic and homogeneous
configuration during inflation. However, couplings to other matter species lead
to particle production, which in turn induces backreaction on and
destabilization of the non-abelian and axion background. In this paper, we
first study the particle production by a gauge field coupled to a
massive Dirac doublet. To carry out this calculation we have made two technical
improvements compared to what has been done in the literature. First, we apply
the anti-symmetrization of the operators to treat particles and anti-particles
on equal footing, second, to deal with the UV divergences, we apply
instantaneous subtraction. We find that, the backreaction of produced fermions
on the background is negligible for model parameters of observational
interest. Next, we consider production of fermions due to coupling to the
axion. The tree-level backreaction on the gauge fields, as well as on the
axion, is vanishingly small. We also provide an estimate for the loop effects.Comment: Matches version accepted for publication in PR
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