279 research outputs found
Spinning compact binary inspiral: Independent variables and dynamically preserved spin configurations
We establish the set of independent variables suitable to monitor the
complicated evolution of the spinning compact binary during the inspiral. Our
approach is valid up to the second post-Newtonian order, including leading
order spin-orbit, spin-spin and mass quadrupol-mass monopole effects, for
generic (noncircular, nonspherical) orbits. Then we analyze the conservative
spin dynamics in terms of these variables. We prove that the only binary black
hole configuration allowing for spin precessions with equal angular velocities
about a common intantaneous axis roughly aligned to the normal of the
osculating orbit, is the equal mass and parallel (aligned or antialigned) spin
configuration. This analytic result puts limitations on what particular
configurations can be selected in numerical investigations of compact binary
evolutions, even in those including only the last orbits of the inspiral.Comment: 13 pages, 2 figures, subsection IV.A improved, published versio
Spinning compact binary dynamics and chameleon orbits
We analyse the conservative evolution of spinning compact binaries to second
post-Newtonian (2PN) order accuracy, with leading order spin-orbit, spin-spin
and mass quadrupole-monopole contributions included. As a main result we derive
a closed system of first order differential equations in a compact form, for a
set of dimensionless variables encompassing both orbital elements and spin
angles. These evolutions are constrained by conservation laws holding at 2PN
order. As required by the generic theory of constrained dynamical systems we
perform a consistency check and prove that the constraints are preserved by the
evolution. We apply the formalism to show the existence of chameleon orbits,
whose local, orbital parameters evolve from elliptic (in the Newtonian sense)
near pericenter, towards hyperbolic at large distances. This behavior is
consistent with the picture that General Relativity predicts stronger gravity
at short distances than Newtonian theory does.Comment: to be published in Phys. Rev. D, 19 pages, 3 figure panel
Spin-dominated waveforms for unequal mass compact binaries
We derive spin-dominated waveforms (SDW) for binary systems composed of
spinning black holes with unequal masses (less than 1:30). Such systems could
be formed by an astrophysical black hole with a smaller black hole or a neutron
star companion; and typically arise for supermassive black hole encounters. SDW
characterize the last stages of the inspiral, when the larger spin dominates
over the orbital angular momentum (while the spin of the smaller companion can
be neglected). They emerge as a double expansion in the post-Newtonian
parameter and the ratio of the orbital angular momentum
and dominant spin. The SDW amplitudes are presented to
() orders, while the phase of the gravitational waves to
() orders (omitting the highest order mixed terms). To
this accuracy the amplitude includes the (leading order) spin-orbit
contributions, while the phase the (leading order) spin-orbit, self-spin and
mass quadrupole-monopole contributions. While the SDW hold for any mass ratio
smaller than 1:30, lower bounds for the mass ratios are derived from the best
sensitivity frequency range expected for Advanced LIGO (giving 1:140), the
Einstein Telescope (), the LAGRANGE () and
LISA missions (), respectively.Comment: 14 pages, 2 figures, 5 tables, published versio
Accretion processes in magnetically and tidally perturbed Schwarzschild black holes
We study the accretion process in the region of the Preston-Poisson
space-time describing a Schwarzschild black hole perturbed by asymptotically
uniform magnetic field and axisymmetric tidal structures. We find that the
accretion disk shrinks and the marginally stable orbit shifts towards the black
hole with the perturbation. The radiation intensity of the accretion disk
increases, while the radius where radiation is maximal remains unchanged. The
spectrum is blue-shifted. Finally, the conversion efficiency of accreting mass
into radiation is decreased by both the magnetic and the tidal perturbations.Comment: to be published in Phys. Rev. D, 13 pages, 7 figures, 1 tabl
2+1+1 GENERAL RELATIVISTIC HAMILTONIAN DYNAMICS AND GAUGE FIXING IN HORNDESKI GRAVITY
A novel 2+1+1 decomposition of space-time based on a nonorthogonal double foliation is worked out and applied for the Hamiltonian description of general relativity, recovering earlier results in the proper limit. The complexity of the formalism allows for an unambiguous gauge-fixing of spherically symmetric, static black hole perturbations in the effective field theory approach of scalar-tensor gravitational theories. This gauge choice is also the closest to the general relativistic Regge-Wheeler gauge
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