4,442 research outputs found
Curvaton Scenario with Affleck-Dine Baryogenesis
We discuss the curvaton scenario with the Affleck-Dine baryogenesis. In this
scenario, non-vanishing baryonic entropy fluctuation may be generated even
without primordial fluctuation of the Affleck-Dine field. Too large entropy
fluctuation is inconsistent with the observations and hence constraints on the
curvaton scenario with the Affleck-Dine baryogenesis are obtained. We calculate
the baryonic entropy fluctuation (as well as other cosmological density
fluctuations) in this case and derive constraints. Implications to some of the
models of the curvaton are also discussed.Comment: 16 pages,2 figure
A-term inflation and the MSSM
The parameter space for A-term inflation is explored with . With p=6 and \lambda_p~1, the observed spectrum and
spectral tilt can be obtained with soft mass of order 10^2 GeV but not with a
much higher mass. The case p=3 requires \lambda_p~10^{-9} to 10^{-12}. The
ratio m/A requires fine-tuning, which may be justified on environmental
grounds. An extension of the MSSM to include non-renormalizable terms and/or
Dirac neutrino masses might support either A-term inflation or modular
inflation.Comment: 10 pages, 3 figures; Comments added, typos correcte
A Complete Supersymmetric SO(10) Model
A complete supersymmetric SO(10) model is constructed, which is the most
general consistent with certain , discrete, and flavor symmetries.
The desired vacuum of the theory has vevs which lie in particular directions of
group space. This leads to both doublet triplet splitting and to the generation
of just four operators for charged fermion masses. The model illustrates how
many features of superunification become related in the context of a complete
theory. The features discussed here include: the weak mixing angle prediction,
the doublet-triplet splitting problem, proton decay, the generation of the
parameter, neutrino masses and the generation of the operators which lead
to charged fermion mass predictions.Comment: 18 page
O(a^2) cutoff effects in lattice Wilson fermion simulations
In this paper we propose to interpret the large discretization artifacts
affecting the neutral pion mass in maximally twisted lattice QCD simulations as
O(a^2) effects whose magnitude is roughly proportional to the modulus square of
the (continuum) matrix element of the pseudoscalar density operator between
vacuum and one-pion state. The numerical size of this quantity is determined by
the dynamical mechanism of spontaneous chiral symmetry breaking and turns out
to be substantially larger than its natural magnitude set by the value of
Lambda_QCD.Comment: 38 pages, 1 figure, 2 table
Particle Production of Vector Fields: Scale Invariance is Attractive
In a model of an Abelian vector boson with a Maxwell kinetic term and non-negative mass-squared it is demonstrated that, under fairly general conditions during inflation, a scale-invariant spectrum of perturbations for the components of a vector field, massive or not, whose kinetic function (and mass) is modulated by the inflaton field is an attractor solution. If the field is massless, or if it remains light until the end of inflation, this attractor solution also generates anisotropic stress, which can render inflation weakly anisotropic. The above two characteristics of the attractor solution can source (independently or combined together) significant statistical anisotropy in the curvature perturbation, which may well be observable in the near future
MSSM Higgses as the source of reheating and all matter
We consider the possibility that the dark energy responsible for inflation is
deposited into extra dimensions outside of our observable universe. Reheating
and all matter can then be obtained from the MSSM flat direction condensate
involving the Higgses and , which acquires large amplitude by virtue
of quantum fluctuations during inflation. The reheat temperature is GeV so that there is no gravitino problem. We find a spectral
index with a very weak dependence on the Higgs potential.Comment: 4 page
Unified Theories with U(2) Flavor Symmetry
A general operator expansion is presented for quark and lepton mass matrices
in unified theories based on a U(2) flavor symmetry, with breaking parameter of
order . While solving the
supersymmetric flavor-changing problem, a general form for the Yukawa couplings
follows, leading to 9 relations among the fermion masses and mixings, 5 of
which are precise. The combination of grand unified and U(2) symmetries
provides a symmetry understanding for the anomalously small values of
and . A fit to the fermion mass data leads to a prediction for the
angles of the CKM unitarity triangle, which will allow a significant test of
these unified U(2) theories. A particular SO(10) model provides a simple
realization of the general operator expansion. The lighter generation masses
and the non-trivial structure of the CKM matrix are generated from the exchange
of a single U(2) doublet of heavy vector generations. This model suggests that
CP is spontaneously broken at the unification scale --- in which case there is
a further reduction in the number of free parameters.Comment: 31 pages, 3 .eps figures include
Magnetic properties of antiferromagnetically coupled CoFeB/Ru/CoFeB
This work reports on the thermal stability of two amorphous CoFeB layers
coupled antiferromagnetically via a thin Ru interlayer. The saturation field of
the artificial ferrimagnet which is determined by the coupling, J, is almost
independent on the annealing temperature up to more than 300 degree C. An
annealing at more than 325 degree C significantly increases the coercivity, Hc,
indicating the onset of crystallization.Comment: 4 pages, 3 figure
- …