3,999 research outputs found
Instabilities in the nonsymmetric theory of gravitation
We consider the linearized nonsymmetric theory of gravitation (NGT) within
the background of an expanding universe and near a Schwarzschild metric. We
show that the theory always develops instabilities unless the linearized
nonsymmetric lagrangian reduces to a particular simple form. This theory
contains a gauge invariant kinetic term, a mass term for the antisymmetric
metric-field and a coupling with the Ricci curvature scalar. This form cannot
be obtained within NGT. Next we discuss NGT beyond linearized level and
conjecture that the instabilities are not a relic of the linearization, but are
a general feature of the full theory. Finally we show that one cannot add
ad-hoc constraints to remove the instabilities as is possible with the
instabilities found in NGT by Clayton.Comment: 29 page
Non-Singular Gravity Without Black Holes
A non-singular, static spherically symmetric solution to the nonsymmetric
gravitational and electromagnetic theory field equations is derived, which
depends on the four parameters m, l^2, Q and s, where m is the mass, Q is the
electric charge, l^2 is the NGT charge of a body and s is a dimensionless
constant. The electromagnetic field invariants are also singularity-free, so
that it is possible to construct regular particle-like solutions in the theory.
All the curvature invariants are finite, there are no null surfaces in the
spacetime and there are no black holes. A new stable, superdense object (SDO)
replaces black holes.Comment: 26 pages, UTPT-94-0
Extraction of black hole coalescence waveforms from noisy data
We describe an independent analysis of LIGO data for black hole coalescence
events. Gravitational wave strain waveforms are extracted directly from the
data using a filtering method that exploits the observed or expected
time-dependent frequency content. Statistical analysis of residual noise, after
filtering out spectral peaks (and considering finite bandwidth), shows no
evidence of non-Gaussian behaviour. There is also no evidence of anomalous
causal correlation between noise signals at the Hanford and Livingston sites.
The extracted waveforms are consistent with black hole coalescence template
waveforms provided by LIGO. Simulated events, with known signals injected into
real noise, are used to determine uncertainties due to residual noise and
demonstrate that our results are unbiased. Conceptual and numerical differences
between our RMS signal-to-noise ratios (SNRs) and the published matched-filter
detection SNRs are discussed.Comment: 15 pages, 11 figures. Version accepted for publicatio
Abelian Anomalies in Nonlocal Regularization
Nonlocal regularization of QED is shown to possess an axial anomaly of the
same form as other regularization schemes. The Noether current is explicitly
constructed and the symmetries are shown to be violated, whereas the identities
constructed when one properly considers the contribution from the path integral
measure are respected. We also discuss the barrier to quantizing the fully
gauged chiral invariant theory, and consequences.Comment: 21 pages, UTPT-93-0
VLT/SINFONI time-resolved spectroscopy of the central, luminous, H-rich WN stars of R136
Using the Very Large Telescope's Spectrograph for INtegral Field Observation
in the Near-Infrared (VLT/SINFONI), we have obtained repeated AO-assisted, NIR
spectroscopy of the six central luminous, Wolf-Rayet (WR) stars in the core of
the very young (~1 Myr), massive and dense cluster R136, in the Large
Magellanic Cloud (LMC). We also de-archived available images that were obtained
with the Hubble Space Telescope's Space Telescope Imaging Spectrograph
(HST/STIS), and extracted high-quality, differential photometry of our target
stars to check for any variability related to binary motion.
Previous studies, relying on spatially unresolved, integrated, optical
spectroscopy, had reported that one of these stars was likely to be a 4.377-day
binary. Our study set out to identify the culprit and any other short-period
system among our targets. However, none displays significant photometric
variability, and only one star, BAT99-112 (R136c), located on the outer fringe
of R136, displays a marginal variability in its radial velocities; we
tentatively report an 8.2-day period. The binary status of BAT99-112 is
supported by the fact that it is one of the brightest X-ray sources among all
known WR stars in the LMC, consistent with it being a colliding-wind system.
Follow-up observations have been proposed to confirm the orbital period of this
potentially very massive system.Comment: 9 pages, 6 figures; accepted for publication in MNRA
Field Equations and Conservation Laws in the Nonsymmetric Gravitational Theory
The field equations in the nonsymmetric gravitational theory are derived from
a Lagrangian density using a first-order formalism. Using the general
covariance of the Lagrangian density, conservation laws and tensor identities
are derived. Among these are the generalized Bianchi identities and the law of
energy-momentum conservation. The Lagrangian density is expanded to
second-order, and treated as an ``Einstein plus fields'' theory. From this, it
is deduced that the energy is positive in the radiation zone.Comment: 16 pages, RevTeX. Additional equations supplie
- …