3,572 research outputs found
Low-scale inflation in a model of dark energy and dark matter
We present a complete particle physics model that explains three major
problems of modern cosmology: inflation, dark matter and dark energy, and also
gives a mechanism for leptogenesis. The model has a new gauge group
that grows strong at a scale eV. We focus on the
inflationary aspects of the model. Inflation occurs with a Coleman-Weinberg
potential at a low scale, down to \sim 6\times 10^5\gev, being compatible
with observational data.Comment: 5 two-column pages, RevTex4; two reference added and minor changes
made in the text; published in JCA
Remote sensing and GIS-based analysis of cave development in the Suoimuoi Catchment (Son La - NW Vietnam)
Integration of remotely sensed imagery with ground surveys is a promising method in cave
development studies. In this research a methodology was set up in which a variety of remote
sensing and GIS techniques support cave analysis in the tropical karst area of the Suoimuoi
catchment, NW Vietnam. In order to extract the maximum information from different remotely
sensed data, the hue invariant IHS transformation was applied to integrate Landsat multispectral
channels with the high resolution Landsat 7 ETM panchromatic channel. The resulting
fused image was used, after enhancement, to visually and digitally extract lineaments.
Aerial photos evaluated the extracted lineaments. Based on lineament density indices a fracture
zone favorable for cave development is defined. The distance between caves and faults
was investigated as well as the correspondence between the cave occurrence and the fracture
zone
Approximate gauge symmetry of composite vector bosons
It can be shown in a solvable field theory model that the couplings of the
composite vector bosons made of a fermion pair approach the gauge couplings in
the limit of strong binding. Although this phenomenon may appear accidental and
special to the vector boson made of a fermion pair, we extend it to the case of
bosons being constituents and find that the same phenomenon occurs in more an
intriguing way. The functional formalism not only facilitates computation but
also provides us with a better insight into the generating mechanism of
approximate gauge symmetry, in particular, how the strong binding and global
current conservation conspire to generate such an approximate symmetry. Remarks
are made on its possible relevance or irrelevance to electroweak and higher
symmetries.Comment: Correction of typos. The published versio
A Model of Quark and Lepton Masses I: The Neutrino Sector
If neutrinos have masses, why are they so tiny? Are these masses of the Dirac
type or of the Majorana type? We are already familiar with the mechanism of how
to obtain a tiny Majorana neutrino mass by the famous see-saw mechanism. The
question is: Can one build a model in which a tiny Dirac neutrino mass arises
in a more or less "natural" way? What would be the phenomenological
consequences of such a scenario, other than just merely reproducing the
neutrino mass patterns for the oscillation data? In this article, a systematic
and detailed analysis of a model is presented, with, as key components, the
introduction of a family symmetry as well as a new SU(2) symmetry for the
right-handed neutrinos. In particular, in addition to the calculations of light
neutrino Dirac masses, interesting phenomenological implications of the model
will be presented.Comment: 25 (single-spaced) pages, 11 figures, corrected some typos in Table
I, added acknowledgement
On Neutrino Masses and Family Replication
The old issue of why there are more than one family of quarks and leptons is
reinvestigated with an eye towards the use of anomaly as a tool for
constraining the number of families. It is found that, by assuming the
existence of right-handed neutrinos (which would imply that neutrinos will have
a mass) and a new chiral SU(2) gauge theory, strong constraints on the number
of families can be obtained. In addition, a model, based on that extra SU(2),
is constructed where it is natural to have one "very heavy" fourth neutrino and
three almost degenerate light neutrinos whose masses are all of the Dirac type.Comment: RevTex, 12 pages with 1 figure, minor changes to the text and added
acknowledgment
Superstring-Inspired E_6 Unification, Shadow Theta-Particles and Cosmology
We construct a new cosmological model considering the superstring-inspired
E_6 unification in the 4-dimensional space at the early stage of the Universe.
We develop a concept of parallel existence in Nature of the ordinary and shadow
worlds with different cosmological evolutions.Comment: 7 page
Minimal SU(5) Resuscitated by Long-Lived Quarks and Leptons
The issue of gauge unification in the (non-supersymmetric) Standard Model is
reinvestigated. It is found that with just an additional fourth generation of
non-sequential and long-lived quarks and leptons, SU(3)xSU(2)xU(1) gauge
couplings converge to a common point of approximately 3.5x10^{15} GeV
(corresponding to a proton lifetime of approximately 10^{34 plus/minus 1}
years). This result is due to the non-negligible- but still perturbative-
contributions of the top and fourth generation Yukawa couplings to the gauge
two-loop beta functions, in contrast with the three generation case where such
a contribution is too small to play an important role in unification.Comment: 12 pages, 2 figure
Mass-Varying Neutrinos from a Variable Cosmological Constant
We consider, in a completely model-independent way, the transfer of energy
between the components of the dark energy sector consisting of the cosmological
constant (CC) and that of relic neutrinos. We show that such a cosmological
setup may promote neutrinos to mass-varying particles, thus resembling a
recently proposed scenario of Fardon, Nelson, and Weiner (FNW), but now without
introducing any acceleronlike scalar fields. Although a formal similarity of
the FNW scenario with the variable CC one can be easily established, one
nevertheless finds different laws for neutrino mass variation in each scenario.
We show that as long as the neutrino number density dilutes canonically, only a
very slow variation of the neutrino mass is possible. For neutrino masses to
vary significantly (as in the FNW scenario), a considerable deviation from the
canonical dilution of the neutrino number density is also needed. We note that
the present `coincidence' between the dark energy density and the neutrino
energy density can be obtained in our scenario even for static neutrino masses.Comment: 8 pages, minor corrections, two references added, to apear in JCA
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