3,422 research outputs found
Conservative self-force correction to the innermost stable circular orbit: comparison with multiple post-Newtonian-based methods
[abridged] Barack & Sago have recently computed the shift of the innermost
stable circular orbit (ISCO) due to the conservative self-force that arises
from the finite-mass of an orbiting test-particle. This is one of the first
concrete results of the self-force program, and provides an exact point of
comparison with approximate post-Newtonian (PN) computations of the ISCO. Here
this exact ISCO shift is compared with nearly all known PN-based methods. These
include both "nonresummed" and "resummed" approaches (the latter reproduce the
test-particle limit by construction). The best agreement with the exact result
is found from effective-one-body (EOB) calculations that are fit to numerical
relativity simulations. However, if one considers uncalibrated methods based
only on the currently known 3PN-order conservative dynamics, the best agreement
is found from the gauge-invariant ISCO condition of Blanchet and Iyer (2003).
This method reproduces the exact test-particle limit without any resummation. A
comparison of PN methods with the equal-mass ISCO is also performed. The
results of this study suggest that the EOB approach---while exactly
incorporating the conservative test-particle dynamics---does not (in the
absence of calibration) incorporate conservative self-force effects more
accurately than standard PN methods. I also consider how the conservative
self-force ISCO shift, combined with numerical relativity computations of the
ISCO, can be used to constrain our knowledge of (1) the EOB effective metric,
(2) phenomenological inspiral-merger-ringdown templates, and (3) 4PN and 5PN
order terms in the PN orbital energy. These constraints could help in
constructing better gravitational-wave templates. Lastly, I suggest a new
method to calibrate unknown PN-terms in inspiral templates using
numerical-relativity calculations.Comment: 27 pages, 2 figures, 2 tables. v2: some changes to Sec. VI in
response to referee comments; references added; other minor changes to match
published versio
Innermost circular orbit of binary black holes at the third post-Newtonian approximation
The equations of motion of two point masses have recently been derived at the
3PN approximation of general relativity. From that work we determine the
location of the innermost circular orbit or ICO, defined by the minimum of the
binary's 3PN energy as a function of the orbital frequency for circular orbits.
We find that the post-Newtonian series converges well for equal masses. Spin
effects appropriate to corotational black-hole binaries are included. We
compare the result with a recent numerical calculation of the ICO in the case
of two black holes moving on exactly circular orbits (helical symmetry). The
agreement is remarkably good, indicating that the 3PN approximation is adequate
to locate the ICO of two black holes with comparable masses. This conclusion is
reached with the post-Newtonian expansion expressed in the standard Taylor
form, without using resummation techniques such as Pad\'e approximants and/or
effective-one-body methods.Comment: 21 pages, to appear in Phys. Rev. D (spin effects appropriate to
corotational black-hole binaries are included; discussion on the validity of
the approximation is added
Quench dynamics of the Ising field theory in a magnetic field
We numerically simulate the time evolution of the Ising field theory after
quenches starting from the integrable model using the Truncated Conformal
Space Approach. The results are compared with two different analytic
predictions based on form factor expansions in the pre-quench and post-quench
basis, respectively. Our results clarify the domain of validity of these
expansions and suggest directions for further improvement. We show for quenches
in the model that the initial state is not of the integrable pair state
form. We also construct quench overlap functions and show that their
high-energy asymptotics are markedly different from those constructed before in
the sinh/sine-Gordon theory, and argue that this is related to properties of
the ultraviolet fixed point
A Monte-Carlo study of the AdS/CFT correspondence: an exploration of quantum gravity effects
In this paper we study the AdS/CFT correspondence for N=4 SYM with gauge
group U(N), compactified on S^3 in four dimensions using Monte-Carlo
techniques. The simulation is based on a particular reduction of degrees of
freedom to commuting matrices of constant fields, and in particular, we can
write the wave functions of these degrees of freedom exactly. The square of the
wave function is equivalent to a probability density for a Boltzman gas of
interacting particles in six dimensions. From the simulation we can extract the
density particle distribution for each wave function, and this distribution can
be interpreted as a special geometric locus in the gravitational dual. Studying
the wave functions associated to half-BPS giant gravitons, we are able to show
that the matrix model can measure the Planck scale directly. We also show that
the output of our simulation seems to match various theoretical expectations in
the large N limit and that it captures 1/N effects as statistical fluctuations
of the Boltzman gas with the expected scaling. Our results suggest that this is
a very promising approach to explore quantum corrections and effects in
gravitational physics on AdS spaces.Comment: 40 pages, 7 figures, uses JHEP. v2: references adde
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