Oscillation modes of ultralight BEC dark matter cores

Structure formation simulations of ultralight bosonic dark matter, ruled by the Gross-Pitaevskii-Poisson (GPP) system of equations, show that dark matter clumps to form structures with density profiles consisting of a core surrounded by a power-law distribution. The core has a density profile similar to that of spherically symmetric equilibrium configurations of the GPP system. These configurations have been shown to be stable under a variety of perturbations and to have attractor properties. It is interesting to know the dominant frequencies of oscillation of these configurations. One reason is that in galaxies the effects of perturbations can trigger observable effects for specific frequency modes. Another reason is that during the process of structure formation, the oscillation modes can help to characterize a core. Based on these motivations, in this manuscript we present a systematic numerical analysis of the reaction of equilibrium configurations to various axi-symmetric perturbations with modes $l=0,1,2,3,4$. We then calculate the first few oscillation frequencies of equilibrium configurations for each mode.Comment: 6 pages, 22 eps figures. Accepted for publication in Phys. Rev.

Answer to the Comment about the Letter entitled ``Scalar fields as dark matter in spiral galaxies''

In this manuscript the authors present a detailed answer to the comment in order to avoid misunderstandings in the future.Comment: 3 pages, latex. An answer to a comment uploaded yesterday: gr-qc/000605

Quintessence at Galactic Level?

Recently it has been proposed that the main contributor to the dark energy of the Universe is a dynamical, slow evolving, spatially inhomogeneous scalar field called quintessence. We investigate the behavior of this scalar field at galactic level by assuming that it is the dark matter compossing the halos of galaxies. Using an exact solution of the Einstein's equations we find an excellent concordance between our results and observations.Comment: 3 pages, 2 .ps figures. Requires REVTe

Spherical non-linear absorption of cosmological scalar fields onto a black hole

In this paper we track the non-linear spherical evolution of a massless scalar field onto a Schwarzschild black hole space-time as a first approximation to the accretion of cosmologically motivated classical scalar fields. We perform an analysis related to wave packets described by wave number and width. We study various values of the wave number k, and found that for k = 0 and width packets bigger than the Schwarzschild radius, the absorption is not total. In the cases we studied for k > 0, the black hole absorbs the total amount of energy density of the scalar field moving toward the horizon. Our results indicate that assuming spherical symmetry, in the non-linear regime, there are cases for which scalar fields are allowed to survive outside black holes and may eventually have life-times consistent with cosmological time scales.Comment: 7 revtex pages, accepted for publication in Phys. Rev.

Modeling long GRBs using a single shock with relativistic radiation hydrodynamics

We explore the possibility that a single relativistic shock, where the gas dynamics is coupled with radiation, can fit the light curves of long GRBs. For this we numerically solve the one dimensional relativistic radiation hydrodynamics equations with a single initial shock. We calculate light curves due to the evolution of this shock in terms of the velocity of the shock, the opacity of the gas, mass density and density of radiated energy. We explore how the variation of each of these parameters provides different features in the light curves. As examples we include the fitting of two long GRBs.Comment: 11 pages, 10 figures, accepted for publication in MNRA

Rotation curves of ultralight BEC dark matter halos with rotation

We study the rotation curves of ultralight BEC dark matter halos. These halos are long lived solutions of initially rotating BEC fluctuations. In order to study the implications of the rotation characterizing these long-lived configurations we consider the particular case of a boson mass $m=10^{-23}\mathrm{eV/c}^2$ and no self-interaction. We find that these halos successfully fit samples of rotation curves (RCs) of LSB galaxies.Comment: 7 pages, 10 eps figures, 1 tables. Accepted for publication in General Relativity and Gravitatio

Characterizing the velocity of a wandering black hole and properties of the surrounding medium using convolutional neural networks

We present a method for estimating the velocity of a wandering black hole and the equation of state for the gas around, based on a catalog of numerical simulations. The method uses machine learning methods based on convolutional neural networks applied to the classification of images resulting from numerical simulations. Specifically we focus on the supersonic velocity regime and choose the direction of the black hole to be parallel to its spin. We build a catalog of 900 simulations by numerically solving Euler's equations onto the fixed space-time background of a black hole, for two parameters: the adiabatic index $\Gamma$ with values in the range [1.1, 5/3], and the asymptotic relative velocity of the black hole with respect to the surroundings $v_{\infty}$, with values within $[0.2, 0.8]c$. For each simulation we produce a 2D image of the gas density once the process of accretion has approached a stationary regime. The results obtained show that the implemented Convolutional Neural Networks are capable to classify correctly the adiabatic index $87.78\%$ of the time within an uncertainty of $\pm 0.0284$ while the prediction of the velocity is correct $96.67\%$ of the times within an uncertainty of $\pm 0.03c$. We expect that this combination of a massive number of numerical simulations and machine learning methods will help analyze more complicated scenarios related to future high resolution observations of black holes, like those from the Event Horizon Telescope.Comment: 5 RevTex pages. Published in Physical Review

Accretion of supersonic winds onto black holes in 3D: stability of the shock cone

Using numerical simulations we present the accretion of supersonic winds onto a rotating black hole in three dimensions. We study five representative directions of the wind with respect to the axis of rotation of the black hole and focus on the evolution and stability of the high density shock cone that is formed during the process. We explore both, the regime in which the shock cone is expected to be stable in order to confirm previous results obtained with two dimensional simulations, and the regime in which the shock cone is expected to show a flip-flop type of instability. The methods used to attempt triggering the instability were first the accumulation of numerical errors and second the explicit application of a perturbation on the velocity field after the shock-cone was formed. The result is negative, that is, we did not find the flip-flop instability within the parameter space we explored, which includes cases that are expected to be unstable.Comment: 9 pages, 25 eps figures. Published in Ap

Spherical Boson Stars as Black Hole mimickers

We present spherically symmetric boson stars as black hole mimickers based on the power spectrum of a simple accretion disk model. The free parameters of the boson star are the mass of the boson and the fourth order self-interaction coefficient in the scalar field potential. We show that even if the mass of the boson is the only free parameter it is possible to find a configuration that mimics the power spectrum of the disk due to a black hole of the same mass. We also show that for each value of the self-interaction a single boson star configuration can mimic a black hole at very different astrophysical scales in terms of the mass of the object and the accretion rate. In order to show that it is possible to distinguish one of our mimickers from a black hole we also study the deflection of light.Comment: 8 revtex pages, 10 eps figure

Estimating the contribution of Alfv\'en waves to the process of heating the quiet solar corona

We solve numerically the ideal MHD equations with an external gravitational field in 2D in order to study the effects of impulsively generated linear and non-linear Alfv\'en waves into isolated solar arcades and coronal funnels. We analyze the region containing the interface between the photosphere and the corona. The main interest is to study the possibility that Alfv\'en waves triggers the energy flux transfer toward the quiet solar corona and heat it, including the case that two consecutive waves can occur. We find that in the case of arcades, short or large, the transferred fluxes by Alfv\'en waves are sufficient to heat the quiet corona only during a small lapse of time and in a certain region. In the case of funnels the threshold is achieved only when the wave is faster than 10 km/s, which is extremely high. We conclude from our analysis, that Alfv\'en waves, even in the optimistic scenario of having two consecutive Alfv\'en wave pulses, cannot transport enough energy as to heat the quiet corona.Comment: 13 pages, 48 png figures. Accepted for publication in MNRA