1,294 research outputs found
Primordial black hole evolution in tensor-scalar cosmology
A perturbative analysis shows that black holes do not remember the value of
the scalar field at the time they formed if changes in
tensor-scalar cosmology. Moreover, even when the black hole mass in the
Einstein frame is approximately unaffected by the changing of , in the
Jordan-Fierz frame the mass increases. This mass increase requires a reanalysis
of the evaporation of primordial black holes in tensor-scalar cosmology. It
also implies that there could have been a significant magnification of the
(Jordan-Fierz frame) mass of primordial black holes.Comment: 4 pages, revte
Measurability of the tidal polarizability of neutron stars in late-inspiral gravitational-wave signals
The gravitational wave signal from a binary neutron star inspiral contains
information on the nuclear equation of state. This information is contained in
a combination of the tidal polarizability parameters of the two neutron stars
and is clearest in the late inspiral, just before merger. We use the recently
defined tidal extension of the effective one-body formalism to construct a
controlled analytical description of the frequency-domain phasing of neutron
star inspirals up to merger. Exploiting this analytical description we find
that the tidal polarizability parameters of neutron stars can be measured by
the advanced LIGO-Virgo detector network from gravitational wave signals having
a reasonable signal-to-noise ratio of . This measurability result
seems to hold for all the nuclear equations of state leading to a maximum mass
larger than . We also propose a promising new way of extracting
information on the nuclear equation of state from a coherent analysis of an
ensemble of gravitational wave observations of separate binary merger events.Comment: 28 pages, 6 figures. Submitted to Phys. Rev.
Wormholes as Black Hole Foils
We study to what extent wormholes can mimic the observational features of
black holes. It is surprisingly found that many features that could be thought
of as ``characteristic'' of a black hole (endowed with an event horizon) can be
closely mimicked by a globally static wormhole, having no event horizon. This
is the case for: the apparently irreversible accretion of matter down a hole,
no-hair properties, quasi-normal-mode ringing, and even the dissipative
properties of black hole horizons, such as a finite surface resistivity equal
to 377 Ohms. The only way to distinguish the two geometries on an
observationally reasonable time scale would be through the detection of
Hawking's radiation, which is, however, too weak to be of practical relevance
for astrophysical black holes. We point out the existence of an interesting
spectrum of quantum microstates trapped in the throat of a wormhole which could
be relevant for storing the information ``lost'' during a gravitational
collapse.Comment: 13 pages, no figures, Late
Phenomenology of the Equivalence Principle with Light Scalars
Light scalar particles with couplings of sub-gravitational strength, which
can generically be called 'dilatons', can produce violations of the equivalence
principle. However, in order to understand experimental sensitivities one must
know the coupling of these scalars to atomic systems. We report here on a study
of the required couplings. We give a general Lagrangian with five independent
dilaton parameters and calculate the "dilaton charge" of atomic systems for
each of these. Two combinations are particularly important. One is due to the
variations in the nuclear binding energy, with a sensitivity scaling with the
atomic number as . The other is due to electromagnetism. We compare
limits on the dilaton parameters from existing experiments.Comment: 5 page
Higher Spins and Open Strings: Quartic Interactions
We analyze quartic gauge-invariant interactions of massless higher spin
fields by using vertex operators constructed in our previous works and
computing their four-point amplitudes in superstring theory. The kinematic part
of the quartic interactions of the higher spins is determined by the matter
structure of their vertex operators;the non-locality of the interactions is the
consequence of specific ghost structure of these operators. We compute
explicitly the four-point amplitude describing the complete gauge-invariant
quartic interaction (two massless spin 3 particles interacting with
two photons) and comment on more general cases, particularly pointing
out the structure of coupling.Comment: 26 pages, misprints corrected, discussion added in the concluding
sectio
Third post-Newtonian accurate generalized quasi-Keplerian parametrization for compact binaries in eccentric orbits
We present Keplerian-type parametrization for the solution of third
post-Newtonian (3PN) accurate equations of motion for two non-spinning compact
objects moving in an eccentric orbit. The orbital elements of the
parametrization are explicitly given in terms of the 3PN accurate conserved
orbital energy and angular momentum in both Arnowitt, Deser, and Misner-type
and harmonic coordinates. Our representation will be required to construct
post-Newtonian accurate `ready to use' search templates for the detection of
gravitational waves from compact binaries in inspiralling eccentric orbits. Due
to the presence of certain 3PN accurate gauge invariant orbital elements, the
parametrization should be useful to analyze the compatibility of general
relativistic numerical simulations involving compact binaries with the
corresponding post-Newtonian descriptions. If required, the present
parametrization will also be needed to compute post-Newtonian corrections to
the currently employed `timing formula' for the radio observations of
relativistic binary pulsars.Comment: 33 pages, 1 figur
Gravitational-wave versus binary-pulsar tests of strong-field gravity
Binary systems comprising at least one neutron star contain strong
gravitational field regions and thereby provide a testing ground for
strong-field gravity. Two types of data can be used to test the law of gravity
in compact binaries: binary pulsar observations, or forthcoming
gravitational-wave observations of inspiralling binaries. We compare the
probing power of these two types of observations within a generic two-parameter
family of tensor-scalar gravitational theories. Our analysis generalizes
previous work (by us) on binary-pulsar tests by using a sample of realistic
equations of state for nuclear matter (instead of a polytrope), and goes beyond
a previous study (by C.M. Will) of gravitational-wave tests by considering more
general tensor-scalar theories than the one-parameter Jordan-Fierz-Brans-Dicke
one. Finite-size effects in tensor-scalar gravity are also discussed.Comment: 23 pages, REVTeX 3.0, uses epsf.tex to include 5 postscript figures
(2 paragraphs and a 5th figure added at the end of section IV + minor
changes
Effective field theory calculation of second post-Newtonian binary dynamics
We use the effective field theory for gravitational bound states, proposed by
Goldberger and Rothstein, to compute the interaction Lagrangian of a binary
system at the second Post-Newtonian order. Throughout the calculation, we use a
metric parametrization based on a temporal Kaluza-Klein decomposition and test
the claim by Kol and Smolkin that this parametrization provides important
calculational advantages. We demonstrate how to use the effective field theory
method efficiently in precision calculations, and we reproduce known results
for the second Post-Newtonian order equations of motion in harmonic gauge in a
straightforward manner.Comment: Replaced with published versio
Light deflection by gravitational waves from localized sources
We study the deflection of light (and the redshift, or integrated time delay)
caused by the time-dependent gravitational field generated by a localized
material source lying close to the line of sight. Our calculation explicitly
takes into account the full, near-zone, plus intermediate-zone, plus wave-zone,
retarded gravitational field. Contrary to several recent claims in the
literature, we find that the deflections due to both the wave-zone 1/r
gravitational wave and the intermediate-zone 1/r^2 retarded fields vanish
exactly. The leading total time-dependent deflection caused by a localized
material source, such as a binary system, is proven to be given by the
quasi-static, near-zone quadrupolar piece of the gravitational field, and
therefore to fall off as the inverse cube of the impact parameter.Comment: 12 pages, REVTeX 3.0, no figur
Generalized soldering of helicity states in
The direct sum of a couple of Maxwell-Chern-Simons (MCS) gauge theories of
opposite helicities does not lead to a Proca theory in ,
although both theories share the same spectrum. However, it is known that by
adding an interference term between both helicities we can join the
complementary pieces together and obtain the physically expected result. A
generalized soldering procedure can be defined to generate the missing
interference term. Here we show that the same procedure can be applied to join
together helicity states in a full off-shell manner. In particular, by
using second-order (in derivatives) self-dual models of helicities
(spin two analogues of MCS models) the Fierz-Pauli theory is obtained after
soldering. Remarkably, if we replace the second-order models by third-order
self-dual models (linearized topologically massive gravity) of opposite
helicities we end up after soldering exactly with the new massive gravity
theory of Bergshoeff, Hohm and Townsend in its linearized approximation.Comment: 12 pages, to appear in Phys. Rev.
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