We study Rotating Boson Star initial data for Numerical Relativity as previously considered by Yoshida and Eriguchi, Lai (arXiv:gr-qc/0410040v2), and Grandclement, Somé and Gourgoulhon (arXiv:1405.4837v3). We use a 3 + 1 decomposition as presented by Gourgoulhon (arXiv:1003.5015v2) and Alcubierre, adapted to an axisymmetric quasi-isotropic spacetime with added regularization at the axis following work by Ruíz, Alcubierre and Núñez (arXiv:0706.0923v2) and Torres. The Einstein-Klein-Gordon equations result in a system of six-coupled, elliptic, nonlinear equations with an added unknown for the scalar field's frequency $ω$. Utilizing a Cartesian two-dimensional grid, finite differences, Global Newton Methods adapted from Deuflhard, the sparse direct linear solver PARDISO, and properly constraining all variables generates data sets for rotation azimuthal integers $l \in [0, 6]$. Our numerical implementation, published in GitHub, is shown to correctly converge both with respect to the resolution size and boundary extension (fourth-order and third-order, respectively). Thus, global parameters such as the Komar masses and angular momenta can be precisely calculated to characterize these spacetimes. Furthermore, analyzing the full family at fixed rotation integer produces maximum masses and minimum frequencies. These coincide with previous results in literature for $l \in [0,2]$ and are new for $l > 2$. In particular, the study of high-amplitude and localized scalar fields in axial symmetry is revealed to be only possible by adding the sixth regularization variable.
In this paper, we construct rotating boson stars composed of the coexisting states of two scalar fields, including the ground and first excited states. We show the coexisting phase with both the ground and first excited states for rotating multistate boson stars. In contrast to the solutions of the nodeless boson stars, the rotating boson stars with two states have two types of nodes, including the $^1S^2S$ state and the $^1S^2P$ state. Moreover, we explore the properties of the mass $M$ of rotating boson stars with two states as a function of the synchronized frequency $ω$, as well as the non…
In this work we present full sets of solutions for rotating charged boson stars with different coupling values. By adopting local comoving coordinates, we are able to find expressions for the effective hydrodynamic quantities of the fluids as seen by this class of observers. We show that not only is the energy density non zero at the center, for the uncharged case it has a local maximum at the core from which it decreases until the point of local minimum where its variation is discontinuous. For the first time, it is reported how rotating boson stars, charged and uncharged, are completely anis…
Boson Stars are stationary, axially symmetric solutions of a complex scalar field theory coupled to gravity. Recently, multi-solitonic configurations interpreted as static chains of multiple Boson Stars bound by gravity and carrying no angular momentum were reported. We propose to generalize those solutions to the stationary case by constructing chains of rotating Boson Stars and analyze their properties. The non-linear elliptic field equations are solved using the finite element method. We find that chains with an even number of constituents exhibit the same spiral-like frequency dependence o…
We investigate the effects ultralight bosonic field dark matter may have on the dynamics of unstable differentially-rotating neutron stars prone to the bar-mode instability. To this aim we perform numerical simulations in general relativity of rotating neutron stars accreting an initial spherically symmetric bosonic field cloud, solving the Einstein-(complex, massive) Klein-Gordon-Euler and the Einstein-(complex) Proca-Euler systems. We find that the presence of the bosonic field can critically modify the development of the bar-mode instability of neutron stars, depending on the total mass of …
In this paper, we study the circular orbit of the spinning test particle in the background of a rotating boson star. Using the pole-dipole approximation and neglecting the back-reaction of the spinning test particle on the spacetime, the equation of motion of the spinning test particle is described by the Mathisson-Papapetrou-Dixon equation. We solve this equation under the Tulczyjew spin-supplementary condition and obtain the four-momentum and four-velocity of the spinning test particle. Quite different from the spinless particle, the effective potential of the spinning particle with zero orb…
The extensivity for the thermodynamics of general $D$-dimensional rotating black holes with or without a cosmological constant can be proved analytically, provided the effective number of microscopic degrees of freedom and the chemical potential are given respectively as $N=L^{D-2}/G, μ= GTI_D/L^{D-2}$, where $G$ is the variable Newton constant, $I_D$ is the Euclidean action and $L$ is a constant length scale. In the cases without a cosmological constant, i.e. the Myers-Perry black holes, the physical mass and the intensive variables can be expressed as explicit macro state functions in the ex…
Rotating Fermion-Boson Stars in $R$-squared Gravity
Universitat de València（瓦伦西亚大学）；Universidad Nacional Autónoma de México（墨西哥国立自治大学）；Sofia University “St. Kliment Ohridski”（索非亚大学（圣克利门特·奥赫里斯基））；Bulgarian Academy of Sciences（保加利亚科学院）
We study the electromagnetic field equation along with the WKB approximation. The boson tunneling phenomenon from charged rotating black ring(CRBR) is analyzed. It is examined that reserve radiation consistent with CRBR can be computed in general by neglecting back reaction and self-gravitational of the radiated boson particle. The calculated temperature depends upon quantum gravity and CRBR geometry. We also examine the corrected tunneling rate/probability of boson particles by assuming charge as well as energy conservation laws and the quantum gravity. Furthermore, we study the graphical beh…
Bargmann-Wigner equations and their solutions are studied in (3+1)-dimensional curved spacetime. Fermion-Boson correspondence for bi-spinor case is studied through the Bargmann-Wigner equations and solutions over curved spacetime. As an application to scattering phenomena of massive Fermions and Bosons on the rotating black holes, the superradiance with negative energy $(ω<0)$ and positive effective energy in co-rotating coordinate system near horizon $(ω-mΩ_{H}>0)$ is possible to occur as stable physical states in Kerr spacetime.
Direct detection of gravitational waves from several compact binary coalescences has ushered in a new era of astronomy. It has opened up the possibility of detecting ultralight bosons, predicted by extensions of the Standard Model, from their gravitational signatures. This is of particular interest as some of these hypothetical particles could be components of dark matter that are expected to interact very weakly with Standard Model particles, if at all, but they would gravitate as usual. Ultralight bosons can trigger superradiant instabilities of rotating black holes and form bosonic clouds t…
It has been shown that scalar fields can form gravitationally bound compact objects called boson stars. In this study, we analyze boson star configurations where the scalar fields contain a small amount of angular momentum and find two new classes of solutions. In the first case all particles are in the same slowly rotating state and in the second case the majority of particles are in the non-rotating ground state and a small number of particles are in an excited rotating state. In both cases, we solve the underlying Gross-Pitaevskii-Poisson equations that describe the profile of these compact…
Boson stars represent a hypothetical exotic type of compact stellar object that may be observed from the gravitational signal of coalescing binaries in current and future GW detectors. In this work we show that the moment of inertia $I$, the (dimensionless) angular momentum $χ$ and the quadrupole moment $Q$ of rotating boson stars obey a universal relation, valid for a wide set of boson star models. Further, the obtained $I-χ-Q~$ relation clearly differs from its famous neutron star counterpart, providing us with an unequivocal diagnostic tool to distinguish boson stars from ordinary compact s…
We study the stability of rotating scalar boson stars, comparing those made from a simple massive complex scalar (referred to as mini boson stars), to those with several different types of nonlinear interactions. To that end, we numerically evolve the nonlinear Einstein-Klein-Gordon equations in 3D, beginning with stationary boson star solutions. We show that the linear, non-axisymmetric instability found in mini boson stars with azimuthal number $m=1$ persists across the entire parameter space for these stars, though the timescale diverges in the Newtonian limit. Therefore, any boson star wit…
