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Title: Halos of unified dark matter scalar field

Abstract

We investigate the static and spherically symmetric solutions of Einstein's equations for a scalar field with a non-canonical kinetic term, assumed to provide both the dark matter and dark energy components of the Universe. In particular, we give a prescription to obtain solutions (dark halos) whose rotation curve v{sub c}(r) is in good agreement with observational data. We show that there exist suitable scalar field Lagrangians that allow us to describe the cosmological background evolution and the static solutions with a single dark fluid.

Authors:
; ;  [1]
  1. Dipartimento di Fisica 'Galileo Galilei', Universita di Padova, and INFN Sezione di Padova, via F Marzolo 8, I-35131 Padova (Italy)
Publication Date:
OSTI Identifier:
22156618
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2008; Journal Issue: 05; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EINSTEIN FIELD EQUATIONS; GALACTIC EVOLUTION; LAGRANGIAN FUNCTION; MATHEMATICAL SOLUTIONS; NONLUMINOUS MATTER; ROTATION; SCALAR FIELDS; SPHERICAL CONFIGURATION; SYMMETRY; UNIVERSE

Citation Formats

Bertacca, Daniele, Bartolo, Nicola, and Matarrese, Sabino, E-mail: daniele.bertacca@pd.infn.it, E-mail: nicola.bartolo@pd.infn.it, E-mail: sabino.matarrese@pd.infn.it. Halos of unified dark matter scalar field. United States: N. p., 2008. Web. doi:10.1088/1475-7516/2008/05/005.
Bertacca, Daniele, Bartolo, Nicola, & Matarrese, Sabino, E-mail: daniele.bertacca@pd.infn.it, E-mail: nicola.bartolo@pd.infn.it, E-mail: sabino.matarrese@pd.infn.it. Halos of unified dark matter scalar field. United States. doi:10.1088/1475-7516/2008/05/005.
Bertacca, Daniele, Bartolo, Nicola, and Matarrese, Sabino, E-mail: daniele.bertacca@pd.infn.it, E-mail: nicola.bartolo@pd.infn.it, E-mail: sabino.matarrese@pd.infn.it. 2008. "Halos of unified dark matter scalar field". United States. doi:10.1088/1475-7516/2008/05/005.
@article{osti_22156618,
title = {Halos of unified dark matter scalar field},
author = {Bertacca, Daniele and Bartolo, Nicola and Matarrese, Sabino, E-mail: daniele.bertacca@pd.infn.it, E-mail: nicola.bartolo@pd.infn.it, E-mail: sabino.matarrese@pd.infn.it},
abstractNote = {We investigate the static and spherically symmetric solutions of Einstein's equations for a scalar field with a non-canonical kinetic term, assumed to provide both the dark matter and dark energy components of the Universe. In particular, we give a prescription to obtain solutions (dark halos) whose rotation curve v{sub c}(r) is in good agreement with observational data. We show that there exist suitable scalar field Lagrangians that allow us to describe the cosmological background evolution and the static solutions with a single dark fluid.},
doi = {10.1088/1475-7516/2008/05/005},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 05,
volume = 2008,
place = {United States},
year = 2008,
month = 5
}
  • We explore unification of dark matter and dark energy in a theory containing a scalar field of non-Lagrangian type, obtained by direct insertion of a kinetic term into the energy-momentum tensor. This scalar is different from quintessence, having an equation of state between -1 and 0 and a zero sound speed in its rest frame. We solve the equations of motion for an exponential potential via a rewriting as an autonomous system, and demonstrate the observational viability of the scenario, for sufficiently small exponential potential parameter {lambda}, by comparison to a compilation of kinematical cosmological data.
  • We use scalar field Lagrangians with a non-canonical kinetic term to obtain unified dark matter models where both the dark matter and the dark energy, the latter mimicking a cosmological constant, are described by the scalar field itself. In this framework, we propose a technique for reconstructing models where the effective speed of sound is small enough that the scalar field can cluster. These models avoid the strong time evolution of the gravitational potential and the large integrated Sachs-Wolfe effect which have been serious drawbacks of models considered previously. Moreover, these unified dark matter scalar field models can be easilymore » generalized to behave as dark matter plus a dark energy component behaving like any type of quintessence fluid.« less
  • We investigate the general properties of Unified Dark Matter (UDM) scalar field models with Lagrangians with a non-canonical kinetic term, looking specifically for models that can produce a fast transition between an early Einstein-de Sitter CDM-like era and a later Dark Energy like phase, similarly to the barotropic fluid UDM models in JCAP01(2010)014. However, while the background evolution can be very similar in the two cases, the perturbations are naturally adiabatic in fluid models, while in the scalar field case they are necessarily non-adiabatic. The new approach to building UDM Lagrangians proposed here allows to escape the common problem ofmore » the fine-tuning of the parameters which plague many UDM models. We analyse the properties of perturbations in our model, focusing on the the evolution of the effective speed of sound and that of the Jeans length. With this insight, we can set theoretical constraints on the parameters of the model, predicting sufficient conditions for the model to be viable. An interesting feature of our models is that what can be interpreted as w{sub DE} can be < −1 without violating the null energy conditions.« less
  • We present an analysis of the cross-correlation between the CMB and the large-scale structure (LSS) of the Universe in Unified Dark Matter (UDM) scalar field cosmologies. We work out the predicted cross-correlation function in UDM models, which depends on the speed of sound of the unified component, and compare it with observations from six galaxy catalogues (NVSS, HEAO, 2MASS, and SDSS main galaxies, luminous red galaxies, and quasars). We sample the value of the speed of sound and perform a likelihood analysis, finding that the UDM model is as likely as the ΛCDM, and is compatible with observations for amore » range of values of c{sub ∞} (the value of the sound speed at late times) on which structure formation depends. In particular, we obtain an upper bound of c{sub ∞}{sup 2} ≤ 0.009 at 95% confidence level, meaning that the ΛCDM model, for which c{sub ∞}{sup 2} = 0, is a good fit to the data, while the posterior probability distribution peaks at the value c{sub ∞}{sup 2} = 10{sup −4} . Finally, we study the time dependence of the deviation from ΛCDM via a tomographic analysis using a mock redshift distribution and we find that the largest deviation is for low-redshift sources, suggesting that future low-z surveys will be best suited to constrain UDM models.« less