35 research outputs found
An exotic k-essence interpretation of interactive cosmological models
We define a generalization of scalar fields with non-canonical kinetic term
which we call exotic k-essence or briefly, exotik. These fields are generated
by the global description of cosmological models with two interactive fluids in
the dark sector and under certain conditions, they correspond to usual
k-essences. The formalism is applied to the cases of constant potential and of
inverse square potential and also we develop the purely exotik version for the
modified holographic Ricci type of dark energy (MHR), where the equations of
state are not constant. With the kinetic function and the inverse
square potential we recover, through the interaction term, the identification
between k-essences and quintessences of exponential potential, already known
for Friedmann-Robertson-Walker and Bianchi type I geometries. Worked examples
are shown that include the self-interacting MHR and also models with crossing
of the phantom divide line (PDL).Comment: Revised version to be published in European Physical Journal
Comments on Unified dark energy and dark matter from a scalar field different from quintessence
In a recent paper by C. Gao, M. Kunz, A. Liddle and D. Parkinson
[arXiv:0912.0949], the unification of dark matter and dark energy was explored
within a theory containing a scalar field of non-Lagrangian type. This scalar
field, different from the classic quintessence, can be obtained from the scalar
field representation of an interacting two-fluid mixture described in the paper
by L.P. Chimento and M. Forte [arXiv:0706.4142
Holographic dark energy linearly interacting with dark matter
We investigate a spatially flat Friedmann-Robertson-Walker (FRW) cosmological
model with cold dark matter coupled to a modified holographic Ricci dark energy
through a general interaction term linear in the energy densities of dark
matter and dark energy, the total energy density and its derivative. Using the
statistical method of -function for the Hubble data, we obtain
km/sMpc, for the asymptotic equation of state and . The estimated values of which fulfill the
current observational bounds corresponds to a dark energy density varying in
the range 0.25R < \ro_x < 0.27R.Comment: March 2012. 6 pp., 6 figures. Note: To appear in the proceedings of
the CosmoSul conference, held in Rio de Janeiro, Brazil, 01-05 august of 201
Modified holographic Ricci dark energy coupled to interacting dark matter and a non interacting baryonic component
We examine a Friedmann-Robertson-Walker universe filled with interacting dark matter, modified holographic Ricci dark energy (MHRDE), and a decoupled baryonic component.The estimations of the cosmic parameters with Hubble data lead to an age of the universe of 13.17 Gyr and show that the MHRDE is free from the cosmic-age problem at low redshift (0 ≤ z ≤ 2) in contrast to holographic Ricci dark energy (HRDE) case. We constrain the parameters with the Union2 data set and contrast with the Hubble data. We also study the behavior of dark energy at early times by taking into account the severe bounds found at recombination era and/or at big bang nucleosynthesis. The inclusion of a non interacting baryonic matter forces that the amount of dark energy at zt ∼ O(1) changes abruptly implying that Ωx(z ≃ 1100) = 0.03, so the bounds reported by the forecast of Planck and CMBPol experiments are more favored for the MHRDE model than in the case of HRDE cutoff. For the former model, we also obtain that at high redshift the fraction of dark energy varies from 0.006 to 0.002, then the amount of Ωx at the big bang nucleosynthesis era does not disturb the observed Helium abundance in the universe provided that the bound Ωx(z ≃ 1010) < 0.21 is hold.Fil: Chimento, Luis Pascual. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Forte, Mónica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Richarte, Martín Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin
Anisotropic k-essence cosmologies
We investigate a Bianchi type-I (BTI) cosmology with k essence and find the
set of models which dissipate the initial anisotropy. There are cosmological
models with extended tachyon fields and k essence having constant bariotropic
index. We obtain the conditions leading to a regular bounce of the average
geometry and the residual anisotropy on the bounce. For constant potential, we
develop purely kinetic k-essence models which are dust dominated in their early
stages, dissipate the initial anisotropy and end in a stable de Sitter
accelerated expansion scenario. We show that linear k field and polynomial
kinetic function models evolve asymptotically to Friedmann-Robertson-Walker
(FRW) cosmologies. The linear case is compatible with an asymptotic potential
interpolating between , in the shear dominated
regime, and at late time. In the polynomial case, the
general solution contains cosmological models with an oscillatory average
geometry. For linear k essence, we find the general solution in the BTI
cosmology when the k field is driven by an inverse square potential. This model
shares the same geometry than a quintessence field driven by an exponential
potential.Comment: 19 pages, REVTeX
Phantom cosmologies and fermions
Form invariance transformations can be used for constructing phantom
cosmologies starting with conventional cosmological models. In this work we
reconsider the scalar field case and extend the discussion to fermionic fields,
where the "phantomization" process exhibits a new class of possible accelerated
regimes. As an application we analyze the cosmological constant group for a
fermionic seed fluid.Comment: 5 pages, version which was accepted for publication in CQ
DInSAR for a Regional Inventory of Active Rock Glaciers in the Dry Andes Mountains of Argentina and Chile with Sentinel-1 Data
The Dry Andes region of Argentina and Chile is characterized by a highly developed periglacial environment. In these arid or semi-arid regions, rock glaciers represent one of the main pieces of evidence of mountain creeping permafrost and water reserves in a solid state. However, their distribution, degree of activity, and response to global warming are not yet well understood. In this context, this work aims to show the potential of the Sentinel-1-based interferometric technique (DInSAR) to map active rock glaciers at a regional level. In particular, the paper presents an active rock glacier inventory for the study area, which covers approximately 40,000 km2, ranging from latitude 30°210S to 33°210S. A total of 2116 active rock glaciers have been detected, and their elevations show a high correlation with the west-east direction. This result was obtained by using only 16 interferometric pairs. Compared to other remote sensing classification techniques, the interferometric technique offers a means to measure surface displacement (active rock glacier). This results in a reliable classification of the degree of activity compared to other methods, based on geomorphological, geomorphometric, and/or ecological criteria. This work presents evidence of this aspect by comparing the obtained results with existing optical data-based inventories. We conclude that the combination of both types of sensors (radar and optical) is an appropriate procedure for active rock glacier inventories, as both mapping methodologies are complementary.Fil: Villarroel, Cristian Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geología; ArgentinaFil: Tamburini Beliveau, Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Rosario; ArgentinaFil: Forte, Ana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Monserrat, Oriol. Agencia Espacial Europea; EspañaFil: Morvillo, Mónica Cristina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentin