508 research outputs found
Naked strong curvature singularities in Szekeres space-times
We investigate the occurrence and nature of naked singularities in the
Szekeres space-times. These space-times represent irrotational dust. They do
not have any Killing vectors and they are generalisations of the
Tolman-Bondi-Lemaitre space-times. It is shown that in these space-times there
exist naked singularities that satisfy both the limiting focusing condition and
the strong limiting focusing condition. The implications of this result for the
cosmic censorship hypothesis are discussed.Comment: latex, 9 page
Data analysis of gravitational-wave signals from spinning neutron stars. II. Accuracy of estimation of parameters
We examine the accuracy of estimation of parameters of the gravitational-wave
signals from spinning neutron stars that can be achieved from observations by
Earth-based laser interferometers. We consider a model of the signal consisting
of two narrowband components and including both phase and amplitude modulation.
We calculate approximate values of the rms errors of the parameter estimators
using the Fisher information matrix. We carry out extensive Monte Carlo
simulations and obtain cumulative distribution functions of rms errors of
astrophysically interesting parameters: amplitude of the signal, wobble angle,
position of the source in the sky, frequency, and spindown coefficients. We
consider both all-sky searches and directed searches. We also examine the
possibility of determination of neutron star proper motion. We perform
simulations for all laser-interferometric detectors that are currently under
construction and for several possible lengths of the observation time and sizes
of the parameter space. We find that observations of continuous
gravitational-wave signals from neutron stars by laser-interferometric
detectors will provide a very accurate information about their astrophysical
properties. We derive several simplified models of the signal that can be used
in the theoretical investigations of the data analysis schemes independently of
the physical mechanisms generating the gravitational-wave signal.Comment: LaTeX, 34 pages, 15 figures, submitted to Phys. Rev.
„Warszawa – Atlas Literatury Zagłady” – kolekcja cyfrowa
The following paper is a review of the innovative project Warszawa – Atlas Literatury Zagłady – kolekcja cyfrowa na platformie Nowa Panorama Literatury Polskiej (NPLP.PL) (Warsaw – Atlas of Holocaust Literature – a digital collection on the platform of the New Panorama of Polish Literature (NPLP.PL)). It is based on testimonies from the time of the occupation, carried out by the Holocaust Literature Research Team and the team of Nowa Panorama Literatury Polskiej IBL PAN (the New Panorama of Polish Literature of the IBL PAN) under the direction of Jacek Leociak and Bartłomiej Szleszyński. The project integrates digital and spatial humanities methodologies to depict the topography of Jewish life and oppression in the Warsaw Ghetto. It focuses on three main categories: Places, Persons and Events, which, when combined, create a multidimensional picture of life in the ghetto. The authors of the project conducted an extensive source search and analysis of texts for topographical data, which made it possible to map the personal geography and experiences of ghetto residents on digital maps.Prezentowany artykuł jest recenzją innowacyjnego projektu Warszawa – Atlas Literatury Zagłady – kolekcja cyfrowa na platformie Nowa Panorama Literatury Polskiej (NPLP.PL). Na podstawie świadectw z czasu okupacji zrealizowanego przez Zespół Badań nad Literaturą Zagłady oraz zespół Nowej Panoramy Literatury Polskiej IBL PAN pod kierunkiem Jacka Leociaka oraz Bartłomieja Szleszyńskiego. Projekt integruje metodologie humanistyki cyfrowej i przestrzennej w celu przedstawienia topografii życia i prześladowań Żydów w getcie warszawskim. Skupia się na trzech głównych kategoriach: Miejsca, Osoby i Wydarzenia, które połączone ze sobą tworzą wielowymiarowy obraz życia w getcie. Autorzy projektu dokonali szerokiej kwerendy źródłowej i analizy tekstów pod kątem danych topograficznych, co pozwoliło na odwzorowanie osobistych geografii i doświadczeń mieszkańców getta na mapach cyfrowych
Gravitational waveforms from inspiralling compact binaries to second-post-Newtonian order
The two independent ``plus" and ``cross" polarization waveforms associated
with the gravitational waves emitted by inspiralling, non-spinning, compact
binaries are presented, ready for use in the data analysis of signals received
by future laser interferometer gravitational-wave detectors such as LIGO and
VIRGO. The computation is based on a recently derived expression of the
gravitational field at the second-post-Newtonian approximation of general
relativity beyond the dominant (Newtonian) quadrupolar field. The use of these
theoretical waveforms to make measurements of astrophysical parameters and to
test the nature of relativistic gravity is discussed.Comment: 17 pages; To appear in Classical and Quantum Gravit
Radial Bargmann representation for the Fock space of type B
Let be the probability and orthogonality measure for the
-Meixner-Pollaczek orthogonal polynomials, which has appeared in
\cite{BEH15} as the distribution of the -Gaussian process (the
Gaussian process of type B) over the -Fock space (the Fock space of
type B). The main purpose of this paper is to find the radial Bargmann
representation of . Our main results cover not only the
representation of -Gaussian distribution by \cite{LM95}, but also of
-Gaussian and symmetric free Meixner distributions on . In
addition, non-trivial commutation relations satisfied by -operators
are presented.Comment: 13 pages, minor changes have been mad
Data analysis of gravitational-wave signals from spinning neutron stars. III. Detection statistics and computational requirements
We develop the analytic and numerical tools for data analysis of the
gravitational-wave signals from spinning neutron stars for ground-based laser
interferometric detectors. We study in detail the statistical properties of the
optimum functional that need to be calculated in order to detect the
gravitational-wave signal from a spinning neutron star and estimate its
parameters. We derive formulae for false alarm and detection probabilities both
for the optimal and the suboptimal filters. We assess the computational
requirements needed to do the signal search. We compare a number of criteria to
build sufficiently accurate templates for our data analysis scheme. We verify
the validity of our concepts and formulae by means of the Monte Carlo
simulations. We present algorithms by which one can estimate the parameters of
the continuous signals accurately.Comment: LaTeX, 45 pages, 13 figures, submitted to Phys. Rev.
On Estimation of the Post-Newtonian Parameters in the Gravitational-Wave Emission of a Coalescing Binary
The effect of the recently obtained 2nd post-Newtonian corrections on the
accuracy of estimation of parameters of the gravitational-wave signal from a
coalescing binary is investigated. It is shown that addition of this correction
degrades considerably the accuracy of determination of individual masses of the
members of the binary. However the chirp mass and the time parameter in the
signal is still determined to a very good accuracy. The possibility of
estimation of effects of other theories of gravity is investigated. The
performance of the Newtonian filter is investigated and it is compared with
performance of post-Newtonian search templates introduced recently. It is shown
that both search templates can extract accurately useful information about the
binary.Comment: 34 pages, 118Kb, LATEX format, submitted to Phys. Rev.
Coherent Line Removal: Filtering out harmonically related line interference from experimental data, with application to gravitational wave detectors
We describe a new technique for removing troublesome interference from
external coherent signals present in the gravitational wave spectrum. The
method works when the interference is present in many harmonics, as long as
they remain coherent with one another. The method can remove interference even
when the frequency changes. We apply the method to the data produced by the
Glasgow laser interferometer in 1996 and the entire series of wide lines
corresponding to the electricity supply frequency and its harmonics are
removed, leaving the spectrum clean enough to detect possible signals
previously masked by them. We also study the effects of the line removal on the
statistics of the noise in the time domain. We find that this technique seems
to reduce the level of non-Gaussian noise present in the interferometer and
therefore, it can raise the sensitivity and duty cycle of the detectors.Comment: 14 pages, 8 figures, Revtex, psfig. To appear in Phys. Rev.
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