1,103 research outputs found
New shifted hybrid inflation
A new shifted hybrid inflationary scenario is introduced which, in contrast
to the older one, relies only on renormalizable superpotential terms. This
scenario is automatically realized in a concrete extension of the "minimal"
supersymmetric Pati-Salam model which naturally leads to a moderate violation
of Yukawa unification so that, for mu>0, the predicted b-quark mass is
acceptable even with universal boundary conditions. It is shown that this
extended model possesses a classically flat "shifted" trajectory which acquires
a slope via one-loop radiative corrections and can be used as inflationary
path. The constraints from the cosmic background explorer can be met with
natural values of the relevant parameters. Also, there is no disastrous
production of magnetic monopoles after inflation since the Pati-Salam gauge
group is already broken on the "shifted" path. The relevant part of inflation
takes place at values of the inflaton field which are not much smaller than the
"reduced" Planck scale and, thus, supergravity corrections could easily
invalidate inflation. It is, however, shown that inflation can be kept intact
provided that an extra gauge singlet with a superheavy vacuum expectation
value, which originates from D-terms, is introduced and a specific form of the
Kaehler potential is used. Moreover, it is found that, although the
supergravity corrections are sizable, the constraints from the cosmic
background explorer can again be met by readjusting the values of the
parameters which were obtained with global supersymmetry.Comment: 18 pages including 1 figure, uses JHEP3.cls, minor corrections,
version to appear in JHE
Continuous growth of vimentin filaments in mouse fibroblasts
We have investigated the dynamics of intermediate filament assembly in vivo by following the fate of heterologous chicken vimentin subunits expressed under the control of an inducible promoter in transfected mouse fibroblasts. Using RNase protection, metabolic protein pulse-chase and immunofluorescence microscopy, we have examined the fate of newly assembled subunits under physiological conditions in situ. Following induction and subsequent removal of inducer, chicken vimentin mRNA had a half-life of approximately 6 h while both chicken and mouse vimentin protein polymer had long half-lives--roughly equivalent to the cell generation time. Moreover, following deinduction, chicken vimentin immunolocalization progressed from a continuous (8-10 h chase) to a discontinuous (> or = 20 h chase) pattern. The continuous chicken vimentin staining reflects the uniform incorporation of chicken vimentin throughout the endogenous mouse vimentin network while the discontinuous or punctate chicken vimentin staining represents short interspersed segments of assembled chicken vimentin superimposed on the endogenous polymer. This punctate staining pattern of chicken vimentin was present throughout the entire array of intermediate filaments, with no bias toward the perinuclear region. These results are consistent with a continuous growth model of intermediate filament assembly, wherein subunit addition occurs at discrete sites located throughout the cytoskeleton
Inflation, Leptogenesis, and Yukawa Quasi-Unification within a Supersymmetric Left-Right Model
A simple extension of the minimal left-right symmetric supersymmetric grand
unified theory model is constructed by adding two pairs of superfields. This
naturally violates the partial Yukawa unification predicted by the minimal
model. After including supergravity corrections, we find that this extended
model naturally supports hilltop F-term hybrid inflation along its trivial
inflationary path with only a very mild tuning of the initial conditions. With
a convenient choice of signs of the terms in the Kahler potential, we can
reconcile the inflationary scale with the supersymmetric grand unified theory
scale. All the current data on the inflationary observables are readily
reproduced. Inflation is followed by non-thermal leptogenesis via the decay of
the right-handed neutrinos emerging from the decay of the inflaton and any
possible washout of the lepton asymmetry is avoided thanks to the violation of
partial Yukawa unification. The extra superfields also assist us in reducing
the reheat temperature so as to satisfy the gravitino constraint. The observed
baryon asymmetry of the universe is naturally reproduced consistently with the
neutrino oscillation parameters.Comment: 20 pages including 4 figure
Constraints on a mixed inflaton and curvaton scenario for the generation of the curvature perturbation
We consider a supersymmetric grand unified model which naturally solves the
strong CP and mu problems via a Peccei-Quinn symmetry and leads to the standard
realization of hybrid inflation. We show that the Peccei-Quinn field of this
model can act as curvaton. In contrast to the standard curvaton hypothesis,
both the inflaton and the curvaton contribute to the total curvature
perturbation. The model predicts an isocurvature perturbation too which has
mixed correlation with the adiabatic one. The cold dark matter of the universe
is mostly constituted by axions plus a small amount of lightest sparticles. The
predictions of the model are confronted with the Wilkinson microwave anisotropy
probe and other cosmic microwave background radiation data. We analyze two
representative choices of parameters and derive bounds on the curvaton
contribution to the adiabatic perturbation. We find that, for the choice which
provides the best fitting of the data, the curvaton contribution to the
adiabatic amplitude must be smaller than about 67% (at 95% confidence level).
The best-fit power spectra are dominated by the adiabatic part of the inflaton
contribution. We use Bayesian model comparison to show that this choice of
parameters is disfavored with respect to the pure inflaton scale-invariant case
with odds of 50 to 1. For the second choice of parameters, the adiabatic mode
is dominated by the curvaton, but this choice is strongly disfavored relative
to the pure inflaton scale-invariant case (with odds of 10^7 to 1). We conclude
that in the present framework the perturbations must be dominated by the
adiabatic component from the inflaton.Comment: 27 pages including 16 figures, uses Revte
Axions and the dark matter of the universe
Spin(10) axion models are constructed which offer the possibility that axions comprise all or a significant part of the dark matter of the Universe
Phosphorylation of Subunit Proteins of Intermediate Filaments from Chicken Muscle and Nonmuscle Cells
The phosphorylation of the subunit proteins of intermediate (10-nm) filaments has been investigated in chicken muscle and nonmuscle cells by using a two-dimensional gel electrophoresis system. Desmin, the 50,000-dalton subunit protein of the intermediate filaments of muscle, had previously been shown to exist as two major isoelectric variants--alpha and ß --in smooth, skeletal, and cardiac chicken muscle. Incubation of skeletal and smooth muscle tissue with 32PO4{}3- reveals that the acidic variant, alpha -desmin, and three other desmin variants are phosphorylated in vivo and in vitro. Under the same conditions, minor components of alpha - and ß -tropomyosin from skeletal muscle, but not smooth muscle, are also phosphorylated. Both the phosphorylated desmin variants and the nonphosphorylated ß -desmin variant remain insoluble under conditions that solubilize actin and myosin filaments, but leave Z-discs and intermediate filaments insoluble. Primary cultures of embryonic chicken muscle labeled with 32PO4{}3- possess, in addition to the desmin variants described above, a major nonphosphorylated and multiple phosphorylated variants of the 52,000-dalton, fibroblast-type intermediate filament protein (IFP). Filamentous cytoskeletons, prepared from primary myogenic cultures by Triton X-100 extraction, contain actin and all of the phosphorylated and nonphosphorylated variants of both desmin and the IFP. Similarly, these proteins are the major components of the caps of aggregated 10-nm filaments isolated from the same cell cultures previously exposed to Colcemid. These results demonstrate that a nonphosphorylated and several phosphorylated variants of desmin and IFP are present in assembled structures in muscle and nonmuscle cells
Nonlinear magnetoinductive transmission lines
Power transmission in one-dimensional nonlinear magnetic metamaterials driven
at one end is investigated numerically and analytically in a wide frequency
range. The nonlinear magnetic metamaterials are composed of varactor-loaded
split-ring resonators which are coupled magnetically through their mutual
inductances, forming thus a magnetoiductive transmission line. In the linear
limit, significant power transmission along the array only appears for
frequencies inside the linear magnetoinductive wave band. We present
analytical, closed form solutions for the magnetoinductive waves transmitting
the power in this regime, and their discrete frequency dispersion. When
nonlinearity is important, more frequency bands with significant power
transmission along the array may appear. In the equivalent circuit picture, the
nonlinear magnetoiductive transmission line driven at one end by a relatively
weak electromotive force, can be modeled by coupled
resistive-inductive-capacitive (RLC) circuits with voltage-dependent
capacitance. Extended numerical simulations reveal that power transmission
along the array is also possible in other than the linear frequency bands,
which are located close to the nonlinear resonances of a single nonlinear RLC
circuit. Moreover, the effectiveness of power transmission for driving
frequencies in the nonlinear bands is comparable to that in the linear band.
Power transmission in the nonlinear bands occurs through the linear modes of
the system, and it is closely related to the instability of a mode that is
localized at the driven site.Comment: 11 pages, 11 figures, submitted to International Journal of
Bifurcation and Chao
Leptogenesis through direct inflaton decay to light particles
We present a scenario of nonthermal leptogenesis following supersymmetric
hybrid inflation, in the case where inflaton decay to both heavy right handed
neutrino and SU(2)_L triplet superfields is kinematically disallowed. Lepton
asymmetry is generated through the decay of the inflaton into light particles
by the interference of one-loop diagrams with right handed neutrino and SU(2)_L
triplet exchange respectively. We require superpotential couplings explicitly
violating a U(1) R-symmetry and R-parity. However, the broken R-parity need not
have currently observable low-energy signatures. Also, the lightest sparticle
can be stable. Some R-parity violating slepton decays may, though, be
detectable in the future colliders. We take into account the constraints from
neutrino masses and mixing and the preservation of the primordial lepton
asymmetry.Comment: 11 pages including 3 figures, uses Revtex, minor corrections,
references adde
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