Correa, C.A.; Wyithe, J.S.B.; Schaye, J.; Duffy, A.R. (2015c) MNRAS, 452, 1217
We present a semi-analytic, physically motivated model for dark matter halo concentration as a function of halo mass and redshift. The semi-analytic model combines an analytic model for the halo mass accretion history (MAH), based on extended Press-Schechter (EPS) theory, with an empirical relation between concentration and formation time obtained through fits to the results of numerical simulations. Because the semi-analytic model is based on EPS theory, it can be applied to wide ranges in mass, redshift and cosmology. The resulting concentration-mass (c-M) relations are found to agree with the simulations, and because the model applies only to relaxed haloes, they do not exhibit the upturn at high masses or high redshifts found by some recent works. We predict a change of slope in the z=0 c-M relation at a mass-scale of 1011M⨀. We find that this is due to the change in the functional form of the halo MAH, which goes from being dominated by an exponential (for high-mass haloes) to a power law (for low-mass haloes). During the latter phase, the core radius remains approximately constant, and the concentration grows due to the drop of the background density. We also analyse how the c-M relation predicted by this work affects the power produced by dark matter annihilation, finding that at z=0 the power is two orders of magnitude lower than that obtained from extrapolating best-fitting c-M relations. We provide fits to the c-M relations as well as numerical routines to compute concentrations and MAHs.
Correa, C.A.; Wyithe, J.S.B.; Schaye, J.; Duffy, A.R. (2015b) MNRAS, 450, 1521.
We explore the relation between the structure and mass accretion histories of dark matter halos using a suite of cosmological simulations. We confirm that the formation time, defined as the time when the virial mass of the main progenitor equals the mass enclosed within the scale radius, correlates strongly with concentration. We provide a semi-analytic model for the halo mass history that combines analytic relations with fits to simulations and where the parameters are directly correlated with concentration. We then combine this model for the halo mass history with the analytic model for halo mass history derived by Correa et al. (2014) to establish the physical link between halo concentration and the initial density perturbation field. Finally, we provide fitting formulas for the halo mass history as well as numerical routines, we derive the accretion rate as a function of halo mass, and we demonstrate how the halo mass history depends on cosmology and the adopted definition of halo mass.
Correa, C.A.; Wyithe, J.S.B.; Schaye, J.; Duffy, A.R. (2015a) MNRAS, 450, 1514.
Understanding the universal accretion history of dark matter halos is the first step towards determining the origin of their structure. In this work we use the extended Press-Schechter formalism to derive the halo mass accretion history from the growth rate of initial density perturbations. We show that the halo mass history is well described by an exponential function of redshift in the high-redshift regime. However, in the low-redshift regime the mass history follows a power law because the growth of density perturbations is halted in the dark energy dominated era due to the accelerated expansion of the Universe. We provide an analytic model for the halo mass history that depends on the linear matter power spectrum. The analytic model does not rely on calibration against numerical simulations and is suitable for any cosmology. We compare our model with the latest empirical models for the mass accretion history in the literature and find very good agreement.
Perez, D.; Romero, G.E.; Correa, C.A.; Perez-Bergiaffa S.E. Published in International Journal of Modern Physics: Conference Series. IF 1.183. IJMPS, 3, 01, 396 (2011).
In this work we address the issue of the thermodynamic behavior of a non-singular spherically-symmetric black hole model, which is described by Schwarschild's solution at large radius and by a de Sitter-like solution at small radius. The interior of the black hole consists of matter fields with sound speed bounded by the speed of light. The matter transits smoothly between normal matter and a core of an exotic fluid. We derive the general equations of the thermodynamic quantities for an arbitrary matter density profile, and adjust the results to the specific regular black hole. We also calculate the Weyl and Kretschmann scalars and analyse the behaviour of the gravitational field in connection with the thermodynamics of the matter fields.
Correa, C.A.; Romero, G.E.; Perez, D.; Perez-Bergiaffa S.E. Published in Bulletin of the Argentinian Astronomical Society. BAAA, 53, 231-234 (2010).
A regular black hole is represented by a singularity-free solution of the Einstein's field equations. One possible set of regular black hole solutions has the geometry of the space-time described by Schwarschild's solution at large radii and by a de Sitter-like solution at small radii. Solutions of this kind can be found for some choices of the equation of state in a static, spherically symmetric configuration. Adopting the equation of state suggested by Mbonye and Kanzanas (2005), the model of the interior of the black hole consists of matter fields with sound speed bounded by the speed of light. In this work we address the question of the thermodynamical behavior of the matter that constitutes the interior of this non-singular black hole model. We derive the general equations of the thermodynamic quantities for an arbitrary density profile and adjust the results to the specific regular black hole. Then, we discuss a possible physical interpretation of the state of regular black hole interiors.
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