0000000000361706
AUTHOR
Juan Carlos Degollado
showing 13 related works from this author
Dynamical formation of a hairy black hole in a cavity from the decay of unstable solitons
2016
Recent numerical relativity simulations within the Einstein--Maxwell--(charged-)Klein-Gordon (EMcKG) system have shown that the non-linear evolution of a superradiantly unstable Reissner-Nordstr\"om black hole (BH) enclosed in a cavity, leads to the formation of a BH with scalar hair. Perturbative evidence for the stability of such hairy BHs has been independently established, confirming they are the true endpoints of the superradiant instability. The same EMcKG system admits also charged scalar soliton-type solutions, which can be either stable or unstable. Using numerical relativity techniques, we provide evidence that the time evolution of some of these $\textit{unstable}$ solitons leads…
Dynamic transition to spontaneous scalarization in boson stars
2010
We show that the phenomenon of spontaneous scalarization predicted in neutron stars within the framework of scalar-tensor tensor theories of gravity, also takes place in boson stars without including a self-interaction term for the boson field (other than the mass term), contrary to what was claimed before. The analysis is performed in the physical (Jordan) frame and is based on a 3+1 decomposition of spacetime assuming spherical symmetry.
Quasistationary solutions of self-gravitating scalar fields around black holes
2015
Recent perturbative studies have shown the existence of long-lived, quasistationary configurations of scalar fields around black holes. In particular, such configurations have been found to survive for cosmological time scales, which is a requirement for viable dark matter halo models in galaxies based on such types of structures. In this paper we perform a series of numerical relativity simulations of dynamical nonrotating black holes surrounded by self-gravitating scalar fields. We solve numerically the coupled system of equations formed by the Einstein and the Klein-Gordon equations under the assumption of spherical symmetry using spherical coordinates. Our results confirm the existence …
Gravitational waves from binary black hole mergers surrounded by scalar field clouds: Numerical simulations and observational implications
2020
We show how gravitational-wave observations of binary black hole (BBH) mergers can constrain the physical characteristics of a scalar field cloud parameterized by mass $\tilde{\mu}$ and strength $\phi_0$ that may surround them. We numerically study the inspiraling equal-mass, non-spinning BBH systems dressed in such clouds, focusing especially on the gravitational-wave signals emitted by their merger-ringdown phase. These waveforms clearly reveal that larger values of $\tilde{\mu}$ or $\phi_0$ cause bigger changes in the amplitude and frequency of the scalar-field-BBH ringdown signals. We show that the numerical waveforms of scalar-field-BBHs can be modelled as chirping sine-Gaussians, with…
Dynamical formation of a Reissner-Nordström black hole with scalar hair in a cavity
2016
In a recent Letter [Sanchis-Gual et al., Phys. Rev. Lett. 116, 141101 (2016)], we presented numerical relativity simulations, solving the full Einstein--Maxwell--Klein-Gordon equations, of superradiantly unstable Reissner-Nordstr\"om black holes (BHs), enclosed in a cavity. Low frequency, spherical perturbations of a charged scalar field trigger this instability. The system's evolution was followed into the nonlinear regime, until it relaxed into an equilibrium configuration, found to be a hairy BH: a charged horizon in equilibrium with a scalar field condensate, whose phase is oscillating at the (final) critical frequency. Here, we investigate the impact of adding self-interactions to the …
Quasistationary solutions of scalar fields around collapsing self-interacting boson stars
2017
There is increasing numerical evidence that scalar fields can form long-lived quasibound states around black holes. Recent perturbative and numerical relativity calculations have provided further confirmation in a variety of physical systems, including both static and accreting black holes, and collapsing fermionic stars. In this work, we investigate this issue yet again in the context of gravitationally unstable boson stars leading to black-hole formation. We build a large sample of spherically symmetric initial models, both stable and unstable, incorporating a self-interaction potential with a quartic term. The three different outcomes of unstable models, namely, migration to the stable b…
Quasistationary solutions of scalar fields around accreting black holes
2016
Massive scalar fields can form long-lived configurations around black holes. These configurations, dubbed quasi-bound states, have been studied both in the linear and nonlinear regimes. In this paper we show that quasi-bound states can form in a dynamical scenario in which the mass of the black hole grows significantly due to the capture of infalling matter. We solve the Klein-Gordon equation numerically in spherical symmetry, mimicking the evolution of the spacetime through a sequence of analytic Schwarzschild black hole solutions of increasing mass. It is found that the frequency of oscillation of the quasi-bound states decreases as the mass of the black hole increases. In addition, accre…
Induced scalarization in boson stars and scalar gravitational radiation
2012
The dynamical evolution of boson stars in scalar-tensor theories of gravity is considered in the physical (Jordan) frame. We focus on the study of spontaneous and induced scalarization, for which we take as initial data configurations on the well-known S-branch of a single boson star in general relativity. We show that during the scalarization process a strong emission of scalar radiation occurs. The new stable configurations (S-branch) of a single boson star within a particular scalar-tensor theory are also presented.
Explosion and Final State of an Unstable Reissner-Nordström Black Hole
2016
A Reissner-Nordstr\"om black hole (BH) is superradiantly unstable against spherical perturbations of a charged scalar field, enclosed in a cavity, with frequency lower than a critical value. We use numerical relativity techniques to follow the development of this unstable system -- dubbed a charged BH bomb -- into the non-linear regime, solving the full Einstein--Maxwell--Klein-Gordon equations, in spherical symmetry. We show that: $i)$ the process stops before all the charge is extracted from the BH; $ii)$ the system settles down into a hairy BH: a charged horizon in equilibrium with a scalar field condensate, whose phase is oscillating at the (final) critical frequency. For low scalar fie…
Quasistationary solutions of self-gravitating scalar fields around collapsing stars
2015
Recent work has shown that scalar fields around black holes can form long-lived, quasistationary configurations surviving for cosmological time scales. Scalar fields thus cannot be discarded as viable candidates for dark matter halo models in galaxies around central supermassive black holes (SMBHs). One hypothesized formation scenario of most SMBHs at high redshift is the gravitational collapse of supermassive stars (SMSs) with masses of $\ensuremath{\sim}{10}^{5}\text{ }\text{ }{\mathrm{M}}_{\ensuremath{\bigodot}}$. Any such scalar field configurations must survive the gravitational collapse of a SMS in order to be a viable model of physical reality. To check for the postcollapse survival …
Dynamical formation and stability of fermion-boson stars
2020
Gravitationally bound structures composed by fermions and scalar particles known as fermion-boson stars are regular and static configurations obtained by solving the coupled Einstein-Klein-Gordon-Euler (EKGE) system. In this work, we discuss one possible scenario through which these fermion-boson stars may form by solving numerically the EKGE system under the simplifying assumption of spherical symmetry. Our initial configurations assume an already existing neutron star surrounded by an accreting cloud of a massive and complex scalar field. The results of our simulations show that once part of the initial scalar field is expelled via gravitational cooling the system gradually oscillates aro…
Numerical evolutions of spherical Proca stars
2017
Vector boson stars, or $\textit{Proca stars}$, have been recently obtained as fully non-linear numerical solutions of the Einstein-(complex)-Proca system. These are self-gravitating, everywhere non-singular, horizonless Bose-Einstein condensates of a massive vector field, which resemble in many ways, but not all, their scalar cousins, the well-known (scalar) $\textit{boson stars}$. In this paper we report fully-non linear numerical evolutions of Proca stars, focusing on the spherically symmetric case, with the goal of assessing their stability and the end-point of the evolution of the unstable stars. Previous results from linear perturbation theory indicate the separation between stable and…
Quasi-stationary solutions of self-gravitating scalar fields around black holes
2014
Recent perturbative studies have shown the existence of long-lived, quasi-stationary configurations of scalar fields around black holes. In particular, such configurations have been found to survive for cosmological timescales, which is a requirement for viable dark matter halo models in galaxies based on such type of structures. In this paper we perform a series of numerical relativity simulations of dynamical non-rotating black holes surrounded by self-gravitating scalar fields. We solve numerically the coupled system of equations formed by the Einstein and the Klein-Gordon equations under the assumption of spherical symmetry using spherical coordinates. Our results confirm the existence …