45 research outputs found
Bound on largest from sub-Planckian excursions of inflaton
In this paper we will discuss the range of large tensor to scalar ratio, ,
obtainable from a sub-Planckian excursion of a {\it single}, {\it slow roll}
driven inflaton field. In order to obtain a large for such a scenario one
has to depart from a monotonic evolution of the slow roll parameters in such a
way that one still satisfies all the current constraints of \texttt{Planck},
such as the scalar amplitude, the tilt in the scalar power spectrum, running
and running of the tilt close to the pivot scale. Since the slow roll
parameters evolve non-monotonically, we will also consider the evolution of the
power spectrum on the smallest scales, i.e. at , to make sure that the amplitude does not become
too large. All these constraints tend to keep the tensor to scalar ratio,
. We scan three different kinds of potential for supersymmetric
flat directions and obtain the benchmark points which satisfy all the
constraints. We also show that it is possible to go beyond
provided we relax the upper bound on the power spectrum on the smallest scales
Number of fermion generations from a novel Grand Unified model
Electroweak interactions based on a gauge group ,
coupled to the QCD gauge group , can predict the number of
generations to be multiples of three. We first try to unify these models within
SU(N) groups, using antisymmetric tensor representations only. After examining
why these attempts fail, we continue to search for an SU(N) GUT that can
explain the number of fermion generations. We show that such a model can be
found for , with fermions in antisymmetric rank-1 and rank-3
representations only, and examine the constraints on various masses in the
model coming from the requirement of unification.Comment: 17 pages, 1 eps figur
Bounds on Neutrino Mass in Viscous Cosmology
Effective field theory of dark matter fluid on large scales predicts the
presence of viscosity of the order of . It has been shown
that this magnitude of viscosities can resolve the discordance between large
scale structure observations and Planck CMB data in the -
and - parameters space. Massive neutrinos suppresses the
matter power spectrum on the small length scales similar to the viscosities. We
show that by including the effective viscosity, which arises from summing over
non linear perturbations at small length scales, severely constrains the
cosmological bound on neutrino masses. Under a joint analysis of Planck CMB and
different large scale observation data, we find that upper bound on the sum of
the neutrino masses at 2- level, decreases from eV (normal hierarchy) and eV (inverted
hierarchy) to eV (normal hierarchy) and eV (inverted hierarchy) when the effective viscosities are included.Comment: 19 pages, 13 figure