234 research outputs found
Instabilities in dark coupled models and constraints from cosmological data
Coupled dark matter-dark energy systems can suffer from non-adiabatic
instabilities at early times and large scales. In these proceedings, we
consider two parameterizations of the dark sector interaction. In the first one
the energy-momentum transfer 4-vector is parallel to the dark matter 4-velocity
and in the second one to the dark energy 4-velocity. In these cases, coupled
models which suffer from non-adiabatic instabilities can be identified as a
function of a generic coupling Q and of the dark energy equation of state. In
our analysis, we do not refer to any particular cosmic field. We confront then
a viable class of models in which the interaction is directly proportional to
the dark energy density and to the Hubble rate parameter to recent cosmological
data. In that framework, we show that correlations between the dark coupling
and several cosmological parameters allow for a larger neutrino mass than in
uncoupled models.Comment: To be published in the proceedings of the Invisible Universe
International Conference (Paris, 29 June - 3 July 2009
Supersymmetric U(1) Gauge Realization of the Dark Scalar Doublet Model of Radiative Neutrino Mass
Adding a second scalar doublet (eta^+,eta^0) and three neutral singlet
fermions N_{1,2,3} to the Standard Model of particle interactions with a new
Z_2 symmetry, it has been shown that Re(eta^0) or Im(eta^0) is a good
dark-matter candidate and seesaw neutrino masses are generated radiatively. A
supersymmetric U(1) gauge extension of this new idea is proposed, which
enforces the usual R parity of the Minimal Supersymmetric Standard Model, and
allows this new Z_2 symmetry to emerge as a discrete remnant.Comment: 8 pages, 3 figure
Utility of a Special Second Scalar Doublet
This Brief Review deals with the recent resurgence of interest in adding a
second scalar doublet (eta^+,eta^0) to the Standard Model of particle
interactions. In most studies, it is taken for granted that eta^0 should have a
nonzero vacuum expectation value, even if it may be very small. What if there
is an exactly conserved symmetry which ensures =0? The phenomenological
ramifications of this idea include dark matter, radiative neutrino mass,
leptogenesis, and grand unification.Comment: 9 pages, 1 figur
Radion Assisted Gauge Inflation
We propose an extension to the recently proposed extranatural or gauge
inflation scenario in which the radius modulus field around which the Wilson
loop is wrapped assists inflation as it shrinks. We discuss how this might lead
to more generic initial conditions for inflation.Comment: 10 pages, 2 figure
Twisted semilocal strings in the MSSM
The standard electroweak model is extended by means of a second
Brout-Englert-Higgs-doublet. The symmetry breaking potential is chosen is such
a way that (i) the Lagrangian possesses a custodial symmetry, (ii) a
stationary, axially symmetric ansatz of the bosonic fields consistently reduces
the Euler-Lagrange equations to a set of differential equations. The potential
involves, in particular, a direct interaction between the two doublets.
Stationary, axially-symmetric solutions of the classical equations are
constructed. Some of them can be assimilated to embedded Nielsen-Olesen
strings. From these solutions there are bifurcations and new solutions appear
which exhibit the characteristics of the recently constructed twisted semilocal
strings. A special emphasis is set on "doubly-twisted" solutions for which the
two doublets present different time-dependent phase factors. They are regular
and have a finite energy which can be lower than the energy of the embedded
twisted solution. Electric-type solutions, such that the fields oscillate
asymptotically far from the symmetry-axis, are also reported.Comment: 17 pages, 11 figures, discussion extended, new solutions obtaine
Biases on cosmological parameters by general relativity effects
General relativistic corrections to the galaxy power spectrum appearing at
the horizon scale, if neglected, may induce biases on the measured values of
the cosmological parameters. In this paper, we study the impact of general
relativistic effects on non standard cosmologies such as scenarios with a time
dependent dark energy equation of state, with a coupling between the dark
energy and the dark matter fluids or with non-Gaussianities. We then explore
whether general relativistic corrections affect future constraints on
cosmological parameters in the case of a constant dark energy equation of state
and of non-Gaussianities. We find that relativistic corrections on the power
spectrum are not expected to affect the foreseen errors on the cosmological
parameters nor to induce large biases on them.Comment: 17 pages, 5 figures, one added figure, results of Tab. I revised,
version accepted for publication in PR
Singlet fermion dark matter and electroweak baryogenesis with radiative neutrino mass
The model of radiative neutrino mass with dark matter proposed by one of us
is extended to include a real singlet scalar field. There are then two
important new consequences. One is the realistic possibility of having the
lightest neutral singlet fermion (instead of the lightest neutral component of
the dark scalar doublet) as the dark matter of the Universe. The other is a
modification of the effective Higgs potential of the Standard Model, consistent
with electroweak baryogenesis.Comment: 9 pages, no figure
The singlet scalar as FIMP dark matter
The singlet scalar model is a minimal extension of the Standard Model that
can explain the dark matter. We point out that in this model the dark matter
constraint can be satisfied not only in the already considered WIMP regime but
also, for much smaller couplings, in the Feebly Interacting Massive Particle
(FIMP) regime. In it, dark matter particles are slowly produced in the early
Universe but are never abundant enough to reach thermal equilibrium or
annihilate among themselves. This alternative framework is as simple and
predictive as the WIMP scenario but it gives rise to a completely different
dark matter phenomenology. After reviewing the calculation of the dark matter
relic density in the FIMP regime, we study in detail the evolution of the dark
matter abundance in the early Universe and the predicted relic density as a
function of the parameters of the model. A new dark matter compatible region of
the singlet model is identified, featuring couplings of order 10^-11 to 10^-12
for singlet masses in the GeV to TeV range. As a consequence, no signals at
direct or indirect detection experiments are expected. The relevance of this
new viable region for the correct interpretation of recent experimental bounds
is emphasized.Comment: 12 pages, 6 figure
Neutrino masses and terms in a supersymmetric extra U(1) model
We propose a supersymmetric extra U(1) model, which can generate small
neutrino masses and necessary terms, simultaneously. Fields including
quarks and leptons are embedded in three s of in a different
way among generations. The model has an extra U(1) gauge symmetry at TeV
regions, which has discriminating features from other models studied
previously. Since a neutrino mass matrix induced in the model has a constrained
texture with limited parameters, it can give a prediction. If we impose
neutrino oscillation data to fix those parameters, a value of
can be determined. We also discuss several phenomenological features which are
discriminated from the ones of the MSSM.Comment: 27 pages, 2 figures, final version for publicatio
Axionic Extensions of the Supersymmetric Standard Model
The Supersymmetric Standard Model is a benchmark theoretical framework for
particle physics, yet it suffers from a number of deficiencies, chief among
which is the strong CP problem. Solving this with an axion in the context of
selected new particles, it is shown in three examples that other problems go
away automatically as well, resulting in (-)^L and (-)^{3B} conservation,
viable combination of two dark-matter candidates, successful baryogenesis,
seesaw neutrino masses, and verifiable experimental consequences at the TeV
energy scale.Comment: 12 pages, 1 figur
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