3,322 research outputs found
Monitoring the Thermal Power of Nuclear Reactors with a Prototype Cubic Meter Antineutrino Detector
In this paper, we estimate how quickly and how precisely a reactor's
operational status and thermal power can be monitored over hour to month time
scales, using the antineutrino rate as measured by a cubic meter scale
detector. Our results are obtained from a detector we have deployed and
operated at 25 meter standoff from a reactor core. This prototype can detect a
prompt reactor shutdown within five hours, and monitor relative thermal power
to three percent within seven days. Monitoring of short-term power changes in
this way may be useful in the context of International Atomic Energy Agency's
(IAEA) Reactor Safeguards Regime, or other cooperative monitoring regimes.Comment: 10 pages, 9 figure
Solving the Hamilton-Jacobi equation for gravitationally interacting electromagnetic and scalar fields
The spatial gradient expansion of the generating functional was recently
developed by Parry, Salopek, and Stewart to solve the Hamiltonian constraint in
Einstein-Hamilton-Jacobi theory for gravitationally interacting dust and scalar
fields. This expansion is used here to derive an order-by-order solution of the
Hamiltonian constraint for gravitationally interacting electromagnetic and
scalar fields. A conformal transformation and functional integral are used to
derive the generating functional up to the terms fourth order in spatial
gradients. The perturbations of a flat Friedmann-Robertson-Walker cosmology
with a scalar field, up to second order in spatial gradients, are given. The
application of this formalism is demonstrated in the specific example of an
exponential potential.Comment: 14 pages, uses amsmath,amssymb, referees' suggestions implemented, to
appear in Classical and Quantum Gravit
Energy of gravitational radiation in plane-symmetric space-times
Gravitational radiation in plane-symmetric space-times can be encoded in a
complex potential, satisfying a non-linear wave equation. An effective energy
tensor for the radiation is given, taking a scalar-field form in terms of the
potential, entering the field equations in the same way as the matter energy
tensor. It reduces to the Isaacson energy tensor in the linearized,
high-frequency approximation. An energy conservation equation is derived for a
quasi-local energy, essentially the Hawking energy. A transverse pressure
exerted by interacting low-frequency gravitational radiation is predicted.Comment: 7 REVTeX4 page
Gravitomagnetic time delay and the Lense-Thirring effect in Brans-Dicke theory of gravity
We discuss the gravitomagnetic time delay and the Lense-Thirring effect in
the context of Brans-Dicke theory of gravity. We compare the theoretical
results obtained with those predicted by general relativity. We show that
within the accuracy of experiments designed to measure these effects both
theories predict essentially the same result.Comment: 10 pages Typeset using REVTE
Importance of including small body spin effects in the modelling of intermediate mass-ratio inspirals. II Accurate parameter extraction of strong sources using higher-order spin effects
We improve the numerical kludge waveform model introduced in [1] in two ways.
We extend the equations of motion for spinning black hole binaries derived by
Saijo et al. [2] using spin-orbit and spin-spin couplings taken from
perturbative and post-Newtonian (PN) calculations at the highest order
available. We also include first-order conservative self-force corrections for
spin-orbit and spin-spin couplings, which are derived by comparison to PN
results. We generate the inspiral evolution using fluxes that include the most
recent calculations of small body spin corrections, spin-spin and spin-orbit
couplings and higher-order fits to solutions of the Teukolsky equation. Using a
simplified version of this model in [1], we found that small body spin effects
could be measured through gravitational wave observations from
intermediate-mass ratio inspirals (IMRIs) with mass ratio eta ~ 0.001, when
both binary components are rapidly rotating. In this paper we study in detail
how the spin of the small/big body affects parameter measurement using a
variety of mass and spin combinations for typical IMRIs sources. We find that
for IMRI events of a moderately rotating intermediate mass black hole (IMBH) of
ten thousand solar masses, and a rapidly rotating central supermassive black
hole (SMBH) of one million solar masses, gravitational wave observations made
with LISA at a fixed signal-to-noise ratio (SNR) of 1000 will be able to
determine the inspiralling IMBH mass, the central SMBH mass, the SMBH spin
magnitude, and the IMBH spin magnitude to within fractional errors of ~0.001,
0.001, 0.0001, and 9%, respectively. LISA can also determine the location of
the source in the sky and the SMBH spin orientation to within ~0.0001
steradians. We show that by including conservative corrections up to 2.5PN
order, systematic errors no longer dominate over statistical errors for IMRIs
with typical SNR ~1000.Comment: 21 pages, 7 figures. v2: three references added, edits in Sections
II-V, including additional results in Section V to address comments by the
referee. v3: mirrors version accepted to PR
Energy Extraction and Particle Acceleration Around Rotating Black Hole in Horava-Lifshitz Gravity
Penrose process on rotational energy extraction of the black hole (BH) in the
original non-projectable Ho\v{r}ava-Lifshitz gravity is studied. The strong
dependence of the extracted energy from the special range of parameters of the
Ho\v{r}ava-Lifshitz gravity, such as parameter and specific angular
momentum has been found. Particle acceleration near the rotating BH in
Ho\v{r}ava-Lifshitz gravity has been studied. It is shown that the fundamental
parameter of the Ho\v{r}ava-Lifshitz gravity can impose limitation on the the
energy of the accelerating particles preventing them from the infinite value.Comment: 6 pages, 3 figures, accepted for publication in Physical Review
Resonantly enhanced and diminished strong-field gravitational-wave fluxes
The inspiral of a stellar mass () compact body into a
massive () black hole has been a focus of much effort,
both for the promise of such systems as astrophysical sources of gravitational
waves, and because they are a clean limit of the general relativistic two-body
problem. Our understanding of this problem has advanced significantly in recent
years, with much progress in modeling the "self force" arising from the small
body's interaction with its own spacetime deformation. Recent work has shown
that this self interaction is especially interesting when the frequencies
associated with the orbit's and motions are in an integer ratio:
, with and
both integers. In this paper, we show that key aspects of the self
interaction for such "resonant" orbits can be understood with a relatively
simple Teukolsky-equation-based calculation of gravitational-wave fluxes. We
show that fluxes from resonant orbits depend on the relative phase of radial
and angular motions. The purpose of this paper is to illustrate in simple terms
how this phase dependence arises using tools that are good for strong-field
orbits, and to present a first study of how strongly the fluxes vary as a
function of this phase and other orbital parameters. Future work will use the
full dissipative self force to examine resonant and near resonant strong-field
effects in greater depth, which will be needed to characterize how a binary
evolves through orbital resonances.Comment: 25 pages, 6 figures, 4 tables. Accepted to Phys Rev D; accepted
version posted here, including referee feedback and other useful comment
Importance of including small body spin effects in the modelling of extreme and intermediate mass-ratio inspirals
We explore the ability of future low-frequency gravitational wave detectors
to measure the spin of stellar mass and intermediate mass black holes that
inspiral onto super-massive Kerr black holes (SMBHs). We develop a kludge
waveform model based on the equations of motion derived by Saijo et al. [Phys
Rev D 58, 064005, 1998] for spinning BH binaries, augmented with spin-orbit and
spin-spin couplings taken from perturbative and post-Newtonian (PN)
calculations, and the associated conservative self-force corrections, derived
by comparison to PN results. We model the inspiral phase using accurate fluxes
which include perturbative corrections for the spin of the inspiralling body,
spin-spin couplings and higher-order fits to solutions of the Teukolsky
equation. We present results of Monte Carlo simulations of parameter estimation
errors and of the model errors that arise when we omit conservative corrections
from the waveform template. For a source 5000+10^6 solar mass observed with an
SNR of 1000, LISA will be able to determine the two masses to within a
fractional error of ~0.001, measure the SMBH spin magnitude, q, and the spin
magnitude of the inspiralling BH to 0.0001, 10%, respectively, and determine
the location of the source in the sky and the SMBH spin orientation to within
0.0001 steradians. For a 10+10^6 solar mass system observed with SNR of 30,
LISA will not be able to determine the spin magnitude of the inspiralling BH,
although the measurement of the other waveform parameters is not significantly
degraded by the presence of spin. The model errors which arise from ignoring
conservative corrections become significant for mass-ratios above 0.0001, but
including these corrections up to 2PN order may be sufficient to reduce these
systematic errors to an acceptable level.Comment: 24 pages, 11 figures. v2 mirrors published version in PRD. Edits in
Sections V and VI in response to comments from refere
Analytic treatment of complete and incomplete geodesics in Taub-NUT space-times
We present the complete set of analytical solutions of the geodesic equation
in Taub-NUT space-times in terms of the Weierstrass elliptic function. We
systematically study the underlying polynomials and characterize the motion of
test particles by its zeros. Since the presence of the "Misner string" in the
Taub-NUT metric has led to different interpretations, we consider these in
terms of the geodesics of the space-time. In particular, we address the
geodesic incompleteness at the horizons discussed by Misner and Taub, and the
analytic extension of Miller, Kruskal and Godfrey, and compare with the
Reissner-Nordstr\"om space-time.Comment: 22 pages, 14 figures, accepted for publication in PR
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