Papers by Ademir Sales de Lima
Linear pertubations in newtonian cosmology with pressure and a cosmological constant
Time-dependent, finite, rotating universes
Journal of Mathematical Physics, 1981
We present three new classes of finite, homogeneous and nonsingular solutions of Einstein’s equat... more We present three new classes of finite, homogeneous and nonsingular solutions of Einstein’s equations which have time-dependent expansion, shear, and rotation. The t-constant sections are of Bianchi type IX. The source of these geometries is a fluid which has not been thermalized.
Several approaches to the matter creation problem in the context of cosmological models are summa... more Several approaches to the matter creation problem in the context of cosmological models are summarily reviewed. A covariant formulation of the general relativistic imperfect simple fluid endowed with a process of matter creation is presented. By considering the standard big bang model, it is shown how the recent results of Prigogine et alii \cite{1} can be recovered and, at the same time their limits of validity are explicited.
Astronomy & Astrophysics, 2011
Context. Observations in the cosmological domain are heavily dependent on the validity of the cos... more Context. Observations in the cosmological domain are heavily dependent on the validity of the cosmic distance-duality (DD) relation, η = D L (z)(1 + z) 2 /D A (z) = 1, an exact result required by the Etherington reciprocity theorem where D L (z) and D A (z) are, respectively, the luminosity and angular diameter distances. In the limit of very small redshifts D A (z) = D L (z) and this ratio is trivially satisfied. Measurements of Sunyaev-Zeldovich effect (SZE) and X-rays combined with the DD relation have been used to determine D A (z) from galaxy clusters. This combination offers the possibility of testing the validity of the DD relation, as well as determining which physical processes occur in galaxy clusters via their shapes. Aims. We use WMAP (7 years) results by fixing the conventional ΛCDM model to verify the consistence between the validity of DD relation and different assumptions about galaxy cluster geometries usually adopted in the literature. Methods. We assume that η is a function of the redshift parametrized by two different relations: η(z) = 1+η 0 z, and η(z) = 1+η 0 z/(1+z), where η 0 is a constant parameter quantifying the possible departure from the strict validity of the DD relation. In order to determine the probability density function (PDF) of η 0 , we consider the angular diameter distances from galaxy clusters recently studied by two different groups by assuming elliptical (isothermal) and spherical (non-isothermal) β models. The strict validity of the DD relation will occur only if the maximum value of η 0 PDF is centered on η 0 = 0. Results. It was found that the elliptical β model is in good agreement with the data, showing no violation of the DD relation (PDF peaked close to η 0 = 0 at 1σ), while the spherical (non-isothermal) one is only marginally compatible at 3σ. Conclusions. The present results derived by combining the SZE and X-ray surface brightness data from galaxy clusters with the latest WMAP results (7-years) favors the elliptical geometry for galaxy clusters. It is remarkable that a local property like the geometry of galaxy clusters might be constrained by a global argument provided by the cosmic DD relation.
The Astrophysical Journal, 2010
In this letter we propose a new and model-independent cosmological test for the distance-duality ... more In this letter we propose a new and model-independent cosmological test for the distance-duality (DD) relation, η = D L (z)(1 + z) −2 /D A (z) = 1, where D L and D A are, respectively, the luminosity and angular diameter distances. For D L we consider two sub-samples of SNe type Ia taken from Constitution data (2009) whereas D A distances are provided by two samples of galaxy clusters compiled by De Fillipis et al. (2005) and Bonamente et al. (2006) by combining Sunyaev-Zeldovich effect (SZE) and X-ray surface brightness. The SNe Ia redshifts of each sub-sample were carefully chosen to coincide with the ones of the associated galaxy cluster sample (∆z < 0.005) thereby allowing a direct test of DD relation. Since for very low redshifts, D A (z) ≅ D L (z), we have tested the DD relation by assuming that η is a function of the redshift parametrized by two different expressions: η(z) = 1 + η 0 z and η(z) = 1 + η 0 z/(1 + z), where η 0 is a constant parameter quantifying a possible departure from the strict validity of the reciprocity relation (η 0 = 0). In the best scenario (linear parametrization) we obtain η 0 = −0.28 +0.44 −0.44 (2σ, statistical + systematic errors) for de Fillipis et al. sample (elliptical geometry), a result only marginally compatible with the DD relation. However, for Bonamente et al. sample (spherical geometry) the constraint is η 0 = −0.42 +0.34 −0.34 (3σ, statistical + systematic errors) which is clearly incompatible with the duality-distance relation.
Astronomy & Astrophysics, 2012
Context. The angular diameter distances toward galaxy clusters can be determined with measurement... more Context. The angular diameter distances toward galaxy clusters can be determined with measurements of Sunyaev-Zel'dovich effect and X-ray surface brightness combined with the validity of the distance-duality relation, D L (z)(1 + z) 2 /D A (z) = 1, where D L (z) and D A (z) are, respectively, the luminosity and angular diameter distances. This combination enables us to probe galaxy cluster physics or even to test the validity of the distance-duality relation itself. Aims. We explore these possibilities based on two different, but complementary approaches. Firstly, in order to constrain the possible galaxy cluster morphologies, the validity of the distance-duality relation (DD relation) is assumed in the ΛCDM framework (WMAP7). Secondly, by adopting a cosmological-model-independent test, we directly confront the angular diameters from galaxy clusters with two supernovae Ia (SNe Ia) subsamples (carefully chosen to coincide with the cluster positions). The influence of the different SNe Ia light-curve fitters in the previous analysis are also discussed. Methods. We assumed that η is a function of the redshift parametrized by two different relations: η(z) = 1 + η 0 z, and η(z) = 1 + η 0 z/(1 + z), where η 0 is a constant parameter quantifying the possible departure from the strict validity of the DD relation. In order to determine the probability density function (PDF) of η 0 , we considered the angular diameter distances from galaxy clusters recently studied by two different groups by assuming elliptical and spherical isothermal β models and spherical non-isothermal β model. The strict validity of the DD relation will occur only if the maximum value of η 0 PDF is centered on η 0 = 0. Results. For both approaches we find that the elliptical β model agrees with the distance-duality relation, whereas the non-isothermal spherical description is, in the best scenario, only marginally compatible. We find that the two-light curve fitters (SALT2 and MLCS2K2) present a statistically significant conflict, and a joint analysis involving the different approaches suggests that clusters are endowed with an elliptical geometry as previously assumed. Conclusions. The statistical analysis presented here provides new evidence that the true geometry of clusters is elliptical. In principle, it is remarkable that a local property such as the geometry of galaxy clusters might be constrained by a global argument like the one provided by the cosmological distance-duality relation.
Journal of Mathematical Physics, 1982
Physics Letters A, 1985
We have obtained a new class of inhomogeneous and anisotropic cosmologies on the assumption of a ... more We have obtained a new class of inhomogeneous and anisotropic cosmologies on the assumption of a fluid not in the thermal equilibrium state as the source of curvature. These solutions generalize Szekeres' parabolic models. One subclass of our solutions evolve to the FRW models at the limit of a large cosmological time, according to Misner's hypothesis.
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Papers by Ademir Sales de Lima