17 research outputs found
Dynamical neutrino masses in the generalized Chaplygin gas scenario with mass varying CDM
Neutrinos coupled to an underlying scalar field in the scenario for
unification of mass varying dark matter and cosmon-{\em like} dark energy is
examined. In the presence of a tiny component of mass varying neutrinos, the
conditions for the present cosmic acceleration and for the stability issue are
reproduced. It is assumed that {\em sterile} neutrinos behave like mass varying
dark matter coupled to mass varying {\em active} neutrinos through the {\em
seesaw} mechanism, in a kind of {\em mixed} dark matter sector. The crucial
point is that the dark matter mass may also exhibit a dynamical behavior driven
by the scalar field. The scalar field mediates the nontrivial coupling between
the mixed dark matter and the dark energy responsible for the accelerated
expansion of the universe. The equation of state of perturbations reproduce the
generalized Chaplygin gas (GCG) cosmology so that all the effective results
from the GCG paradigm are maintained, being perturbatively modified by
neutrinos.Comment: 19 pages, 5 figure
Equilibrium and stability of neutrino lumps as TOV solutions
We report about stability conditions for static, spherically symmetric
objects that share the essential features of mass varying neutrinos in
cosmological scenarios. Compact structures of particles with variable mass are
held together preponderantly by an attractive force mediated by a background
scalar field. Their corresponding conditions for equilibrium and stability are
given in terms of the ratio between the total mass-energy and the spherical
lump radius, . We show that the mass varying mechanism leading to lump
formation can modify the cosmological predictions for the cosmological neutrino
mass limits. Our study comprises Tolman-Oppenheimer-Volkoff solutions of
relativistic objects with non-uniform energy densities. The results leave open
some questions concerning stable regular solutions that, to an external
observer, very closely reproduce the preliminary conditions to form
Schwarzschild black holes.Comment: 20 pages, 5 figure
Coupling active and sterile neutrinos in the cosmon plus seesaw framework
The cosmological evolution of neutrino energy densities driven by cosmon-type
field equations is introduced assuming that active and sterile neutrinos are
intrinsically connected by cosmon fields through the {\em seesaw} mechanism.
Interpreting sterile neutrinos as dark matter adiabatically coupled with dark
energy results in a natural decoupling of (active) mass varying neutrino
(MaVaN) equations. Identifying the dimensionless scale of the {\em seesaw}
mechanism, , with a power of the cosmological scale factor, , allows
for embedding the resulting masses into the generalized Chaplygin gas (GCG)
scenario for the dark sector. Without additional assumptions, our findings
establish a precise connection among three distinct frameworks: the cosmon
field dynamics for MaVaN's, the {\em seesaw} mechanism for dynamical mass
generation and the GCG scenario. Our results also corroborate with previous
assertions that mass varying particles can be the right responsible for the
stability issue and for the cosmic acceleration of the universe.Comment: 12 pages, 2 figure
Developing a Conceptual Framework of Landscape and Hydrology on Tallgrass Prairie:A Critical Zone Approach
Agricultural intensification and urbanization have greatly reduced the extent of tallgrass prairie across North America. To evaluate the impact of these changes, a reference ecosystem of unperturbed prairie is required. The Konza Prairie Biological Station in northeastern Kansas is a long-term research site at which a critical zone approach has been implemented. Integration of climatic, ecologic, and hydropedologic research to facilitate a comprehensive understanding of the complex environment provides the basis for predicting future aquifer and landscape evolution. We present a conceptual framework of the hydrology underpinning the area that integrates the extensive current and past research and provides a synthesis of the literature to date. The key factors in the hydrologic behavior of Konza Prairie are climate, ecology, vadose zone characteristics and management, and groundwater and bedrock. Significant interactions among these factors include bedrock dissolution driven by cool-season precipitation and hence a climatic control on the rate of karstification. Soil moisture dynamics are influenced at various timescales due to the short- and long-term effects of prescribed burning on vegetation and on soil physical characteristics. The frequency of burning regimes strongly influences the expansion of woody species in competition with native tallgrasses, with consequent effects on C and N dynamics within the vadose zone. Knowledge gaps exist pertaining to the future of Konza Prairie (a model for US tallgrass prairie)—whether continued karstification will lead to increasingly flashy and dynamic hydrology and whether compositional changes in the vegetation will affect long-term changes in water balances
The Hamiltonian formalism for scalar fields coupled to gravity in a cosmological background
Reorganization of a deeply incised drainage: role of deformation, sedimentation and groundwater flow
Deeply incised drainage networks are thought to be robust and not easily
modified, and are commonly used as passive markers of horizontal strain.
Yet, reorganizations (rearrangements) appear in the geologic record. We
provide field evidence of the reorganization of a Miocene drainage
network in response to strike-slip and vertical displacements in
Guatemala. The drainage was deeply incised into a 50-km-wide orogen
located along the North America-Caribbean plate boundary. It rearranged
twice, first during the Late Miocene in response to transpressional
uplift along the Polochic fault, and again in the Quaternary in response
to transtensional uplift along secondary faults. The pattern of
reorganization resembles that produced by the tectonic defeat of rivers
that cross growing tectonic structures. Compilation of remote sensing
data, field mapping, sediment provenance study, grain-size analysis and
Ar(40)/Ar(39) dating from paleovalleys and their fill reveals that the
classic mechanisms of river diversion, such as river avulsion over
bedrock, or capture driven by surface runoff, are not sufficient to
produce the observed diversions. The sites of diversion coincide
spatially with limestone belts and reactivated fault zones, suggesting
that solution-triggered or deformation-triggered permeability have
helped breaching of interfluves. The diversions are also related
temporally and spatially to the accumulation of sediment fills in the
valleys, upstream of the rising structures. We infer that the breaching
of the interfluves was achieved by headward erosion along tributaries
fed by groundwater flow tracking from the valleys soon to be captured.
Fault zones and limestone belts provided the pathways, and the aquifers
occupying the valley fills provided the head pressure that enhanced
groundwater circulation. The defeat of rivers crossing the rising
structures results essentially from the tectonically enhanced activation
of groundwater flow between catchments