3,660 research outputs found
LISA observations of supermassive black holes: parameter estimation using full post-Newtonian inspiral waveforms
We study parameter estimation of supermassive black hole binary systems in
the final stage of inspiral using the full post-Newtonian gravitational
waveforms. We restrict our analysis to systems in circular orbit with
negligible spins, in the mass range 10^8\Ms-10^5\Ms, and compare the results
with those arising from the commonly used restricted post-Newtonian
approximation. The conclusions of this work are particularly important with
regard to the astrophysical reach of future LISA measurements. Our analysis
clearly shows that modeling the inspiral with the full post-Newtonian waveform,
not only extends the reach to higher mass systems, but also improves in general
the parameter estimation. In particular, there are remarkable improvements in
angular resolution and distance measurement for systems with a total mass
higher than 5\times10^6\Ms, as well as a large improvement in the mass
determination.Comment: Final version. Accepted for publication in Phys. Rev.
Matched-filter study and energy budget suggest no detectable gravitational-wave 'extended emission' from GW170817
Van Putten & Della Valle (2018) have reported a possible detection of
gravitational-wave 'extended emission' from a neutron star remnant of GW170817.
Starting from the time-frequency evolution and total emitted energy of their
reported candidate, we show that such an emission is not compatible with the
current understanding of neutron stars. We explore the additional required
physical assumptions to make a full waveform model, for example, taking the
optimistic emission from a spining-down neutron star with fixed quadrupolar
deformation, and study whether even an ideal single-template matched-filter
analysis could detect an ideal, fully phase-coherent signal. We find that even
in the most optimistic case an increase in energy and extreme parameters would
be required for a confident detection with LIGO sensitivity as of 2018-08-17.
The argument also holds for other waveform models following a similar
time-frequency track and overall energy budget. Single-template matched
filtering on the LIGO data around GW170817, and on data with added simulated
signals, verifies the expected sensitivity scaling and the overall statistical
expectation.Comment: 9 pages, 6 figures, updated version as accepted by MNRA
Emission spectrum of quasi-resonant laterally coupled quantum dots
We calculate the emission spectrum of neutral and charged excitons in a pair
of laterally coupled InGaAs quantum dots with nearly degenerate energy levels.
As the interdot distance decreases, a number of changes take place in the
emission spectrum which can be used as indications of molecular coupling. These
signatures ensue from the stronger tunnel-coupling of trions as compared to
that of neutral excitons.Comment: 7 pages, 7 figure
Volatility and dividend risk in perpetual American options
American options are financial instruments that can be exercised at any time
before expiration. In this paper we study the problem of pricing this kind of
derivatives within a framework in which some of the properties --volatility and
dividend policy-- of the underlaying stock can change at a random instant of
time, but in such a way that we can forecast their final values. Under this
assumption we can model actual market conditions because some of the most
relevant facts that may potentially affect a firm will entail sharp predictable
effects. We will analyse the consequences of this potential risk on perpetual
American derivatives, a topic connected with a wide class of recurrent problems
in physics: holders of American options must look for the fair price and the
optimal exercise strategy at once, a typical question of free absorbing
boundaries. We present explicit solutions to the most common contract
specifications and derive analytical expressions concerning the mean and higher
moments of the exercise time.Comment: 21 pages, 5 figures, iopart, submitted for publication; deep
revision, two new appendice
PatologĂa escapulo-clavicular en un sujeto de Morella
X Congreso Nacional de PaleopatologĂa. Univesidad AutĂłnoma de Madrid, septiembre de 200
PatologĂa de ligamentos en la meseta tibial
X Congreso Nacional de PaleopatologĂa. Univesidad AutĂłnoma de Madrid, septiembre de 200
Accuracy and effectualness of closed-form, frequency-domain waveforms for non-spinning black hole binaries
The coalescences of binary black hole (BBH) systems, here taken to be
non-spinning, are among the most promising sources for gravitational wave (GW)
ground-based detectors, such as LIGO and Virgo. To detect the GW signals
emitted by BBHs, and measure the parameters of the source, one needs to have in
hand a bank of GW templates that are both effectual (for detection), and
accurate (for measurement). We study the effectualness and the accuracy of the
two types of parametrized banks of templates that are directly defined in the
frequency-domain by means of closed-form expressions, namely 'post-Newtonian'
(PN) and 'phenomenological' models. In absence of knowledge of the exact
waveforms, our study assumes as fiducial, target waveforms the ones generated
by the most accurate version of the effective one body (EOB) formalism. We find
that, for initial GW detectors the use, at each point of parameter space, of
the best closed-form template (among PN and phenomenological models) leads to
an effectualness >97% over the entire mass range and >99% in an important
fraction of parameter space; however, when considering advanced detectors, both
of the closed-form frequency-domain models fail to be effectual enough in
significant domains of the two-dimensional [total mass and mass ratio]
parameter space. Moreover, we find that, both for initial and advanced
detectors, the two closed-form frequency-domain models fail to satisfy the
minimal required accuracy standard in a very large domain of the
two-dimensional parameter space. In addition, a side result of our study is the
determination, as a function of the mass ratio, of the maximum frequency at
which a frequency-domain PN waveform can be 'joined' onto a NR-calibrated EOB
waveform without undue loss of accuracy.Comment: 29 pages, 8 figures, 1 table. Accepted for publication in Phys. Rev.
Massive relativistic particle model with spin from free two-twistor dynamics and its quantization
We consider a relativistic particle model in an enlarged relativistic phase
space M^{18} = (X_\mu, P_\mu, \eta_\alpha, \oeta_\dalpha, \sigma_\alpha,
\osigma_\dalpha, e, \phi), which is derived from the free two-twistor dynamics.
The spin sector variables (\eta_\alpha, \oeta_\dalpha, \sigma_\alpha,\
osigma_\dalpha) satisfy two second class constraints and account for the
relativistic spin structure, and the pair (e,\phi) describes the electric
charge sector. After introducing the Liouville one-form on M^{18}, derived by a
non-linear transformation of the canonical Liouville one-form on the
two-twistor space, we analyze the dynamics described by the first and second
class constraints. We use a composite orthogonal basis in four-momentum space
to obtain the scalars defining the invariant spin projections. The
first-quantized theory provides a consistent set of wave equations, determining
the mass, spin, invariant spin projection and electric charge of the
relativistic particle. The wavefunction provides a generating functional for
free, massive higher spin fields.Comment: FTUV-05-0919, IFIC-05-46, IFT UWr 0110/05. Plain latex file, no
macros, 22 pages. A comment and references added. To appear in PRD1
TendinopatĂa de una clavĂcula: estudio anatĂłmico y paleopatolĂłgico
X Congreso Nacional de PaleopatologĂa. Univesidad AutĂłnoma de Madrid, septiembre de 200
- …