185 research outputs found
Physical Origin, Evolution and Observational Signature of Diffused Antiworld
The existence of macroscopic regions with antibaryon excess in the baryon
asymmetric Universe with general baryon excess is the possible consequence of
practically all models of baryosynthesis. Diffusion of matter and antimatter to
the border of antimatter domains defines the minimal scale of the antimatter
domains surviving to the present time. A model of diffused antiworld is
considered, in which the density within the surviving antimatter domains is too
low to form gravitationally bound objects. The possibility to test this model
by measurements of cosmic gamma ray fluxes is discussed. The expected gamma ray
flux is found to be acceptable for modern cosmic gamma ray detectors and for
those planned for the near future.Comment: 9 page
Inflation with a Weyl term, or ghosts at work
In order to assess the role of ghosts in cosmology, we study the evolution of
linear cosmological perturbations during inflation when a Weyl term is added to
the action. Our main result is that vector perturbations can no longer be
ignored and that scalar modes diverge in the newtonian gauge but remain bounded
in the comoving slicing.Comment: 14 pages, 4 figure
The large-scale modulation of the density distribution in standard axionic CDM and its cosmological and physical impact
It is shown, that the energy density of coherent axion field oscillations in
the cosmology of standard invisible axion should be distributed in the Universe
in the form of archioles, being nonlinear inhomogeneous structure, reflecting
the large scale distribution of Brownian structure of axion strings in the very
early Universe. Spectrum of inhomogeneities, generated by archioles, is
obtained and their effects in the spectrum and quadrupole anisotropy of relic
radiation are considered. The axionic-string-decay-model-independent
restriction on the scale of axion interaction is obtained.Comment: 8 pages, Talk presented at Workshop on Fundamental Physics at the
Birth of the Universe II, Roma, May 19-24, 199
Searches for violation of fundamental time reversal and space reflection symmetries in solid state experiments
The electric dipole moment (EDM) of a particle violates both time reversal
(T) and space reflection (P) symmetries. There have been recent suggestions for
searches of the electron EDM using solid state experiments [1,2]. These
experiments could improve the sensitivity compared to present atomic and
molecular experiments by several orders of magnitude. In the present paper we
calculate the expected effect. We also suggest that this kind of experiment is
sensitive to T,P-violation in nuclear forces and calculate effects caused by
the nuclear Schiff moment.
The compounds under consideration contain magnetic Gd ions and oxygen
O ions. We demonstrate that the main mechanism for the T,P-odd effects
is related to the penetration of the Oxygen 2p-electrons to the Gd core. All
the effects are related to the deformation of the crystal lattice.Comment: 13 pages, 6 figure
Electromagnetic waves in an axion-active relativistic plasma non-minimally coupled to gravity
We consider cosmological applications of a new self-consistent system of
equations, accounting for a nonminimal coupling of the gravitational,
electromagnetic and pseudoscalar (axion) fields in a relativistic plasma. We
focus on dispersion relations for electromagnetic perturbations in an initially
isotropic ultrarelativistic plasma coupled to the gravitational and axion
fields in the framework of isotropic homogeneous cosmological model of the de
Sitter type. We classify the longitudinal and transversal electromagnetic modes
in an axionically active plasma and distinguish between waves (damping,
instable or running), and nonharmonic perturbations (damping or instable). We
show that for the special choice of the guiding model parameters the
transversal electromagnetic waves in the axionically active plasma,
nonminimally coupled to gravity, can propagate with the phase velocity less
than speed of light in vacuum, thus displaying a possibility for a new type of
resonant particle-wave interactions.Comment: 19 pages, 9 figures, published versio
Horizontal symmetry in Higgs sector of GUT with U(1)_A symmetry
In a series of papers, we pointed out that an anomalous gauge
symmetry naturally solves various problems in grand unified theories (GUTs) and
that a horizontal gauge symmetry, or , not only realizes the
unification of three generation quarks and leptons in fewer multiplets but also
solves the supersymmetric flavor problem. In this paper, we examine the
possibility that the Higgs sectors of the GUT symmetry and of the horizontal
symmetry are unified, that is, there are some Higgs fields whose vacuum
expectation values (VEVs) break both the GUT gauge symmetry and the horizontal
symmetry at the same time. Although the scale of the VEVs become too large to
suppress the flavor changing neutral current processes sufficiently, the
unification is possible. In addition, for the models, the
gauge anomaly is cancelled in the unified models without introducing additional
fields in contrast with the previous models in which the Higgs sectors are not
unified.Comment: 35 page
From weak-scale observables to leptogenesis
Thermal leptogenesis is an attractive mechanism for generating the baryon
asymmetry of the Universe. However, in supersymmetric models, the parameter
space is severely restricted by the gravitino bound on the reheat temperature
. For hierarchical light neutrino masses, it is shown that thermal
leptogenesis {\it can} work when GeV. The low-energy
observable consequences of this scenario are . For higher , thermal leptogenesis works in a
larger area of parameter space, whose observable consequences are more
ambiguous. A parametrisation of the seesaw in terms of weak-scale inputs is
used, so the results are independent of the texture chosen for the GUT-scale
Yukawa matrices.Comment: a few references adde
Neutrino Oscillations v.s. Leptogenesis in SO(10) Models
We study the link between neutrino oscillations and leptogenesis in the
minimal framework assuming an SO(10) see-saw mechanism with 3 families. Dirac
neutrino masses being fixed, the solar and atmospheric data then generically
induce a large mass-hierarchy and a small mixing between the lightest
right-handed neutrinos, which fails to produce sufficient lepton asymmetry by 5
orders of magnitudes at least. This failure can be attenuated for a very
specific value of the mixing sin^2(2\theta_{e3})=0.1, which interestingly lies
at the boundary of the CHOOZ exclusion region, but will be accessible to future
long baseline experiments.Comment: 23 pages, 8 eps figures, JHEP3 format; more accurate effect of
dilution reduces previous results, inclusion of all phases, added reference
Robust Limits on Lorentz Violation from Gamma-Ray Bursts
We constrain the possibility of a non-trivial refractive index in free space
corresponding to an energy-dependent velocity of light: c(E) \simeq c_0 (1 -
E/M), where M is a mass scale that might represent effect of
quantum-gravitational space-time foam, using the arrival times of sharp
features observed in the intensities of radiation with different energies from
a large sample of gamma-ray bursters (GRBs) with known redshifts. We use
wavelet techniques to identify genuine features, which we confirm in
simulations with artificial added noise. Using the weighted averages of the
time-lags calculated using correlated features in all the GRB light curves, we
find a systematic tendency for more energetic photons to arrive earlier.
However, there is a very strong correlation between the parameters
characterizing an intrinsic time-lag at the source and a distance-dependent
propagation effect. Moreover, the significance of the earlier arrival times is
less evident for a subsample of more robust spectral structures. Allowing for
intrinsic stochastic time-lags in these features, we establish a statistically
robust lower limit: M > 0.9x10^{16} GeV on the scale of violation of Lorentz
invariance.Comment: 18 pages, 4 eps figure
On primordial trispectrum from exchanging scalar modes in general multiple field inflationary models
We make an complementary investigation of the primordial trispectrum from
exchanging intermediate scalar modes in multi-field inflation models with
generalized kinetic terms. Together with the calculation of irreducible
contributions to the primordial trispectrum in Ref.[103], we give the full
leading-order primordial trispectrum in generalized multi-field models.Comment: 15 pages, 1 figure; v2 references adde
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