We discuss possible origins for discrepancies observed in the radiated energies in head-on collisions of non-spinning binaries starting from Brill-Lindquist and superposed Kerr-Schild data. For this purpose, we discuss the impact of different choices of gauge parameters and a small initial boost of the black holes.
We report a degeneracy between the gravitational-wave signals from quasi-circular precessing black-hole mergers and those from extremely eccentric mergers, namely head-on collisions. Performing model selection on numerically simulated signals of head-on collisions using models for quasi-circular binaries we find that, for signal-to-noise ratios of 15 and 25, typical of Advanced LIGO observations, head-on mergers with respective total masses of $M\in (125,300)M_\odot$ and $M\in (200,440)M_\odot$ would be identified as precessing quasi-circular intermediate-mass black hole binaries, located at a…
The collision of black holes and the emission of gravitational radiation in higher-dimensional spacetimes are of interest in various research areas, including the gauge-gravity duality, the TeV gravity scenarios evoked for the explanation of the hierarchy problem, and the large-dimensionality limit of general relativity. We present numerical simulations of head-on collisions of nonspinning, unequal-mass black holes starting from rest in general relativity with $4 \leq D\leq 10$ spacetime dimensions. We compare the energy and linear momentum radiated in gravitational waves with perturbative pre…
Density profiles of ultralight Bose-Condensate dark matter inferred from numerical simulations of structure formation, ruled by the Gross-Pitaevskii-Poisson (GPP) system of equations, have a core-tail structure. Multi-state equilibrium configurations of the GPP system on the other hand, have a similar core-tail density profile. We now submit these multi-state configurations to highly dynamical scenarios and show their potential as providers of appropriate density profiles of structures. What we do is to present the simulation of head-on collisions between two equilibrium configurations of the …
Proca stars are self-gravitating Bose-Einstein condensates obtained as numerical stationary solutions of the Einstein-(complex)-Proca system. These solitonic can be both stable and form dynamically from generic initial data by the mechanism of gravitational cooling. In this paper we further explore the dynamical properties of these solitonic objects by performing both head-on collisions and orbital mergers of equal mass Proca stars, using fully non-linear numerical evolutions. For the head-on collisions, we show that the end point and the gravitational waveform from these collisions depends on…
Fully non-linear numerical evolutions of the Einstein-(multi)--Klein-Gordon equations are performed to study head-on collisions of $\ell$-boson stars. Despite being spherically symmetric, $\ell$-boson stars have a (hidden) frame of reference, used in defining their individual multipolar fields. To assess the impact of their relative orientation, we perform simulations with different angles between the axes of the two colliding stars. Additionally, two scenarios are considered for the colliding stars: that they are composites of either the same or different scalar fields. Despite some model-spe…
If two particles move toward a black hole and collide near the horizon, the energy E_{c.m.} in the centre of mass can grow unbounded. This is a so-called Bañados-Silk-West (BSW) effect. One of problems creating obstacles to the possibility of its observation consists in that individual energy E of a fragment at infinity remains finite because of redshift. We show that in the case of head-on collision, debris may have unbounded energy E. An essential ingredient of this scenario is a particle moving away from a black hole in the near-horizon region. It can appear due to precedent collision that …
We study linearized equations of a ghost-free gravity in four- and higher-dimensional spacetimes. We consider versions of such a theory where the nonlocal modification of the $\Box$ operator has the form $\Box \exp[(-\Box/μ^2)^N]$, where $N=1$ or $N=2n$. We first obtain the Newtonian gravitational potential for a point mass for such models and demonstrate that it is finite and regular in any number of spatial dimensions $d\ge 3$. The second result of the paper is calculation of the gravitational field of an ultrarelativistic particle in such theories. And finally, we study a head-on collision …
Results are presented from numerical simulations of the flat-space nonlinear Maxwell-Klein-Gordon equations demonstrating deep inelastic scattering of $m=1$ vortices for a range of Ginzburg-Landau (or Abelian-Higgs) parameters ($κ$), impact parameters ($b$), and initial velocities ($v_0$). The threshold ($v_0^*$) of right-angle scattering is explored for head-on ($b=0$) collisions by varying $v_0$. Solutions obey time-scaling laws, $T\propto α\ln(v_0-v_0^*) $, with $κ$-dependent scaling exponents, $α$, and have $v_0^*$ that appear not to have the previously reported upper bound. The arbitraril…
Boson star-black hole binaries: initial data and head-on collisions
Hangzhou Institute for Advanced Study (HIAS), University of Chinese Academy of Sciences (UCAS)（杭州高等研究院，中国科学院大学）；Institute of Theoretical Physics, Chinese Academy of Sciences (CAS)（中国科学院理论物理研究所）；University of Chinese Academy of Sciences (UCAS)（中国科学院大学）
Extreme mass ratio head-on collisions of black holes in Einstein-scalar-Gauss-Bonnet theory
SISSA, International School for Advanced Studies（国际高等研究院）；INFN, Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）；Universidad de Alcalá（阿尔卡拉大学）；University of Hertfordshire（赫特福德大学）；ISCTE – Instituto Universitário de Lisboa（里斯本大学学院）；Universidade de Lisboa - UL（里斯本大学）；Instituto de Telecomunicações–IUL（电信研究所）
We use fully nonlinear numerical relativity techniques to study high energy head-on collision of nonspinning, equal-mass black holes to estimate the maximum gravitational radiation emitted by these systems. Our simulations include improvements in the construction of initial data, subsequent full numerical evolutions, and the computation of waveforms at infinity. The new initial data significantly reduces the spurious radiation content, allowing for initial speeds much closer to the speed of light, i.e. $v\sim0.99c$. Using these new techniques, We estimate the maximum radiated energy from head-…
The collision of two equilibrium ground state solutions of the Schrödinger-Poisson (SP) system, in orthogonal states, is proposed as a formation mechanism of mixed state solutions of the SP system with spherical and first dipolar components. The collisions are simulated by solving numerically the SP system for two orthogonal states, considering head-on encounters, and using various mass ratios between the initial configurations with different head-on momentum. The results indicate that the less massive of the configurations pinches-off the more massive one, and redistributes its density along …
