35 research outputs found
Gravitational Wave Chirp Search: Economization of PN Matched Filter Bank via Cardinal Interpolation
The final inspiral phase in the evolution of a compact binary consisting of
black holes and/or neutron stars is among the most probable events that a
network of ground-based interferometric gravitational wave detectors is likely
to observe. Gravitational radiation emitted during this phase will have to be
dug out of noise by matched-filtering (correlating) the detector output with a
bank of several templates, making the computational resources required
quite demanding, though not formidable. We propose an interpolation method for
evaluating the correlation between template waveforms and the detector output
and show that the method is effective in substantially reducing the number of
templates required. Indeed, the number of templates needed could be a factor
smaller than required by the usual approach, when the minimal overlap
between the template bank and an arbitrary signal (the so-called {\it minimal
match}) is 0.97. The method is amenable to easy implementation, and the various
detector projects might benefit by adopting it to reduce the computational
costs of inspiraling neutron star and black hole binary search.Comment: scheduled for publicatin on Phys. Rev. D 6
Time transfer and frequency shift to the order 1/c^4 in the field of an axisymmetric rotating body
Within the weak-field, post-Newtonian approximation of the metric theories of
gravity, we determine the one-way time transfer up to the order 1/c^4, the
unperturbed term being of order 1/c, and the frequency shift up to the order
1/c^4. We adapt the method of the world-function developed by Synge to the
Nordtvedt-Will PPN formalism. We get an integral expression for the
world-function up to the order 1/c^3 and we apply this result to the field of
an isolated, axisymmetric rotating body. We give a new procedure enabling to
calculate the influence of the mass and spin multipole moments of the body on
the time transfer and the frequency shift up to the order 1/c^4. We obtain
explicit formulas for the contributions of the mass, of the quadrupole moment
and of the intrinsic angular momentum. In the case where the only PPN
parameters different from zero are beta and gamma, we deduce from these results
the complete expression of the frequency shift up to the order 1/c^4. We
briefly discuss the influence of the quadrupole moment and of the rotation of
the Earth on the frequency shifts in the ACES mission.Comment: 17 pages, no figure. Version 2. Abstract and Section II revised. To
appear in Physical Review
Relativistic Celestial Mechanics with PPN Parameters
Starting from the global parametrized post-Newtonian (PPN) reference system
with two PPN parameters and we consider a space-bounded
subsystem of matter and construct a local reference system for that subsystem
in which the influence of external masses reduces to tidal effects. Both the
metric tensor of the local PPN reference system in the first post-Newtonian
approximation as well as the coordinate transformations between the global PPN
reference system and the local one are constructed in explicit form. The terms
proportional to reflecting a violation of the
equivalence principle are discussed in detail. We suggest an empirical
definition of multipole moments which are intended to play the same role in PPN
celestial mechanics as the Blanchet-Damour moments in General Relativity.
Starting with the metric tensor in the local PPN reference system we derive
translational equations of motion of a test particle in that system. The
translational and rotational equations of motion for center of mass and spin of
each of extended massive bodies possessing arbitrary multipole structure
are derived. As an application of the general equations of motion a
monopole-spin dipole model is considered and the known PPN equations of motion
of mass monopoles with spins are rederived.Comment: 71 page
Optimum Placement of Post-1PN GW Chirp Templates Made Simple at any Match Level via Tanaka-Tagoshi Coordinates
A simple recipe is given for constructing a maximally sparse regular lattice
of spin-free post-1PN gravitational wave chirp templates subject to a given
minimal match constraint, using Tanaka-Tagoshi coordinates.Comment: submitted to Phys. Rev.
Curvature-corrected dilatonic black holes and black hole -- string transition
We investigate extremal charged black hole solutions in the four-dimensional
string frame Gauss-Bonnet gravity with the Maxwell field and the dilaton.
Without curvature corrections, the extremal electrically charged dilatonic
black holes have singular horizon and zero Bekenstein entropy. When the
Gauss-Bonnet term is switched on, the horizon radius expands to a finite value
provided curvature corrections are strong enough. Below a certain threshold
value of the Gauss-Bonnet coupling the extremal black hole solutions cease to
exist. Since decreasing Gauss-Bonnet coupling corresponds to decreasing string
coupling , the situation can tentatively be interpreted as classical
indication on the black hole -- string transition. Previously the extremal
dilaton black holes were studied in the Einstein-frame version of the
Gauss-Bonnet gravity. Here we work in the string frame version of this theory
with the S-duality symmetric dilaton function as required by the heterotic
string theory.Comment: 14 pages, 2 figure
Vacuum Polarization in the Spacetime of a Scalar-Tensor Cosmic String
We study the vacuum polarization effect in the spacetime generated by a
magnetic flux cosmic string in the framework of a scalar-tensor gravity. The
vacuum expectation values of the energy-momentum tensor of a conformally
coupled scalar field are calculated. The dilaton's contribution to the vacuum
polarization effect is shown explicitly.Comment: 11 pages, LATEX file, 2 eps figure
Chiral spinors and gauge fields in noncommutative curved space-time
The fundamental concepts of Riemannian geometry, such as differential forms,
vielbein, metric, connection, torsion and curvature, are generalized in the
context of non-commutative geometry. This allows us to construct the
Einstein-Hilbert-Cartan terms, in addition to the bosonic and fermionic ones in
the Lagrangian of an action functional on non-commutative spaces. As an
example, and also as a prelude to the Standard Model that includes
gravitational interactions, we present a model of chiral spinor fields on a
curved two-sheeted space-time with two distinct abelian gauge fields. In this
model, the full spectrum of the generalized metric consists of pairs of tensor,
vector and scalar fields. They are coupled to the chiral fermions and the gauge
fields leading to possible parity violation effects triggered by gravity.Comment: 50 pages LaTeX, minor corrections and references adde
Background independent action for double field theory
Double field theory describes a massless subsector of closed string theory
with both momentum and winding excitations. The gauge algebra is governed by
the Courant bracket in certain subsectors of this double field theory. We
construct the associated nonlinear background-independent action that is
T-duality invariant and realizes the Courant gauge algebra. The action is the
sum of a standard action for gravity, antisymmetric tensor, and dilaton fields
written with ordinary derivatives, a similar action for dual fields with dual
derivatives, and a mixed term that is needed for gauge invariance.Comment: 45 pages, v2: minor corrections, refs. added, to appear in JHE
Testing the stability of fundamental constants with the 199Hg+ single-ion optical clock
Over a two-year duration, we have compared the frequency of the 199Hg+ 5d106s
2S 1/2 (F=0) 5d9 6s2 2D 5/2 (F=2) electric-quadrupole transition at 282 nm
with the frequency of the ground-state hyperfine splitting in neutral 133Cs.
These measurements show that any fractional time variation of the ratio
nu(Cs)/nu(Hg) between the two frequencies is smaller than +/- 7 10^-15 / yr (1
sigma uncertainty). According to recent atomic structure calculations, this
sets an upper limit to a possible fractional time variation of g(Cs) m_e / m_p
alpha^6.0 at the same level.Comment: 4 pages with 3 figures. RevTeX 4, Submitted to Phys. Rev. Let
Cosmic optical activity in the spacetime of a scalar-tensor screwed cosmic string
Measurements of radio emission from distant galaxies and quasars verify that
the polarization vectors of these radiations are not randomly oriented as
naturally expected. This peculiar phenomenon suggests that the spacetime
intervening between the source and observer may be exhibiting some sort of
optical activity, the origin of which is not known. In the present paper we
provide a plausible explanation to this phenomenon by investigating the r\^ole
played by a Chern-Simons-like term in the background of an ordinary or
superconducting screwed cosmic string in a scalar-tensor gravity. We discuss
the possibility that the excess in polarization of the light from
radio-galaxies and quasars can be understood as if the electromagnetic waves
emitted by these cosmic objects interact with a scalar-tensor screwed cosmic
string through a Chern-Simons coupling. We use current astronomical data to
constrain possible values for the coupling constant of this theory, and show
that it turns out to be: eV, which is two orders of
magnitude larger than in string-inspired theories.Comment: Revised version, to appear in Phys. Rev.