157 research outputs found
Testing Scalar-Tensor Gravity Using Space Gravitational-Wave Interferometers
We calculate the bounds which could be placed on scalar-tensor theories of
gravity of the Jordan, Fierz, Brans and Dicke type by measurements of
gravitational waveforms from neutron stars (NS) spiralling into massive black
holes (MBH) using LISA, the proposed space laser interferometric observatory.
Such observations may yield significantly more stringent bounds on the
Brans-Dicke coupling parameter \omega than are achievable from solar system or
binary pulsar measurements. For NS-MBH inspirals, dipole gravitational
radiation modifies the inspiral and generates an additional contribution to the
phase evolution of the emitted gravitational waveform. Bounds on \omega can
therefore be found by using the technique of matched filtering. We compute the
Fisher information matrix for a waveform accurate to second post-Newtonian
order, including the effect of dipole radiation, filtered using a currently
modeled noise curve for LISA, and determine the bounds on \omega for several
different NS-MBH canonical systems. For example, observations of a 1.4 solar
mass NS inspiralling to a 1000 solar mass MBH with a signal-to-noise ratio of
10 could yield a bound of \omega > 240,000, substantially greater than the
current experimental bound of \omega > 3000.Comment: 18 pages, 4 figures, 1 table; to be submitted to Phys. Rev.
Ixodes (Afrixodes) drakensbergensis n. sp. from domestic and wild animals in Natal, Republic of South Africa
Ixodes (Afrixodes) drakensbergensis n. sp., is described from females, males, nymphs and larvae
collected on a drag at Giant's Castle Nature Reserve, Natal, Republic of South Africa; it was also
taken from an eland in the same area and from goats and a cow in the adjacent Tank Area 118. The
occurrence of I. (A.) drakensbergensis on domestic animals suggests that it may be of economic
importance in this area. Information is provided to separate the new species from other closely
related Ixodes species that occur or may occur in this region.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi.
Adobe Acroabt XI was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
Ixodes (Afrixodes) bakeri Authur & Cliford, 1961 (Acarina : Ixodidae): description of the male and immature stages from rodents and insectivores and notes on its biology in South Africa
The male, nymph and larva of Ixodes (A.) bakeri are described and illustrated with line drawings
and scanning electron microscope photographs. This species was originally described from 1 female
from Otomys sp., Nyika Plateau, Malawi. The present material consists of 28 collections from
insectivores and 19 collections from rodents, Van Riebeeck Nature Reserve, Transvaal, plus 1
collection from a rodent in the Jonkershoek Valley, Cape Province, Republic of South Africa.
Its biology in South Africa is also discussed.The articles have been scanned in colour with a HP scanjet 5590; 300dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to final presentyation PDF-Format
Ixodes (Afrixodes) neitzi, n. sp. (Acarina :Ixo didae) from the mountain reedbuck in South Africa
Ixodes (Afrixodes) neitzi n. sp. is described from females and males collected from the mountain reedbuck (Redunca fulvorufula) at Loskop Dam Nature Reserve, Transvaal, Republic of South Africa. Information is provided to distinguish this new species from other closely related Ixodes species that occur in the Ethiopian region.
Its predilection sites are noted and the area in which it occurs is described briefly.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
Clarification of the status of Rhipicephalus kochi Dönitz, 1905 (Ixodoidea, Ixodidae)
Figures of the types of Rhipicephalus kochi, and of its synonym Rhipicephalus neavei Warburton, 1912, are presented. These are accompanied by complete descriptions of all stages of R. kochi, illustrated with scanning electron microscope photographs. The basic differences between this species, Rhipicephalus pravus Dönitz, 1910 and Rhipicephalus punctatus Warburton, 1912 are outlined.
R. kochi occurs south of the Equator in parts of eastern, central and southern Africa. Its adults feed most commonly on cattle, various antelopes and wild pigs, and on hares. Little is known about the hosts of the immature stages; nymphae have been recorded in a field collection once only, from Petrodromus tetradactylus, the 4-toed elephant shrew.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
Ixodes (Afrixodes) matopi n. sp. (Acarina: Ixodidae) : a tick found aggregating on pre-orbital gland scent marks of the klipspringer in Zimbabwe
Ixodes (Afrixodes) matopi n. sp. is described from females and males collected off twigs bearing deposits of intraspecific communication marks secreted by the pre-orbital glands of the klipspringer Oreotragus oreotragus and from laboratory-reared immature specimens. One female was also found on a goat.
The 4 collections were all from Zimbabwe, 3 of them from Matabeleland South Province and the fourth from Inyanga District, Zimbabwe.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
Application of energy and angular momentum balance to gravitational radiation reaction for binary systems with spin-orbit coupling
We study gravitational radiation reaction in the equations of motion for
binary systems with spin-orbit coupling, at order (v/c)^7 beyond Newtonian
gravity, or O(v/c)^2 beyond the leading radiation reaction effects for
non-spinning bodies. We use expressions for the energy and angular momentum
flux at infinity that include spin-orbit corrections, together with an
assumption of energy and angular momentum balance, to derive equations of
motion that are valid for general orbits and for a class of coordinate gauges.
We show that the equations of motion are compatible with those derived earlier
by a direct calculation.Comment: 12 pages, submitted to General Relativity and Gravitatio
General Brane Geometries from Scalar Potentials: Gauged Supergravities and Accelerating Universes
We find broad classes of solutions to the field equations for d-dimensional
gravity coupled to an antisymmetric tensor of arbitrary rank and a scalar field
with non-vanishing potential. Our construction generates these configurations
from the solution of a single nonlinear ordinary differential equation, whose
form depends on the scalar potential. For an exponential potential we find
solutions corresponding to brane geometries, generalizing the black p-branes
and S-branes known for the case of vanishing potential. These geometries are
singular at the origin with up to two (regular) horizons. Their asymptotic
behaviour depends on the parameters of the model. When the singularity has
negative tension or the cosmological constant is positive we find
time-dependent configurations describing accelerating universes. Special cases
give explicit brane geometries for (compact and non-compact) gauged
supergravities in various dimensions, as well as for massive 10D supergravity,
and we discuss their interrelation. Some examples lift to give new solutions to
10D supergravity. Limiting cases with a domain wall structure preserve part of
the supersymmetries of the vacuum. We also consider more general potentials,
including sums of exponentials. Exact solutions are found for these with up to
three horizons, having potentially interesting cosmological interpretation. We
give several additional examples which illustrate the power of our techniques.Comment: 54 pages, 6 figures. Uses JHEP3. Published versio
Gravitational waves from inspiralling compact binaries: Parameter estimation using second-post-Newtonian waveforms
The parameters of inspiralling compact binaries can be estimated using
matched filtering of gravitational-waveform templates against the output of
laser-interferometric gravitational-wave detectors. Using a recently calculated
formula, accurate to second post-Newtonian (2PN) order [order , where
is the orbital velocity], for the frequency sweep () induced by
gravitational radiation damping, we study the statistical errors in the
determination of such source parameters as the ``chirp mass'' , reduced
mass , and spin parameters and (related to spin-orbit and
spin-spin effects, respectively). We find that previous results using template
phasing accurate to 1.5PN order actually underestimated the errors in ,
, and . For two inspiralling neutron stars, the measurement errors
increase by less than 16 percent.Comment: 14 pages, ReVTe
- …