773 research outputs found
First upper limit analysis and results from LIGO science data: stochastic background
I describe analysis of correlations in the outputs of the three LIGO
interferometers from LIGO's first science run, held over 17 days in August and
September of 2002, and the resulting upper limit set on a stochastic background
of gravitational waves. By searching for cross-correlations between the LIGO
detectors in Livingston, LA and Hanford, WA, we are able to set a 90%
confidence level upper limit of h_{100}^2 Omega_0 < 23 +/- 4.6.Comment: 7 pages; 1 eps figures; proceeding from 2003 Edoardo Amaldi Meeting
on Gravitational Wave
The Primordial Gravitational Wave Background in String Cosmology
We find the spectrum P(w)dw of the gravitational wave background produced in
the early universe in string theory. We work in the framework of String Driven
Cosmology, whose scale factors are computed with the low-energy effective
string equations as well as selfconsistent solutions of General Relativity with
a gas of strings as source. The scale factor evolution is described by an early
string driven inflationary stage with an instantaneous transition to a
radiation dominated stage and successive matter dominated stage. This is an
expanding string cosmology always running on positive proper cosmic time. A
careful treatment of the scale factor evolution and involved transitions is
made. A full prediction on the power spectrum of gravitational waves without
any free-parameters is given. We study and show explicitly the effect of the
dilaton field, characteristic to this kind of cosmologies. We compute the
spectrum for the same evolution description with three differents approachs.
Some features of gravitational wave spectra, as peaks and asymptotic
behaviours, are found direct consequences of the dilaton involved and not only
of the scale factor evolution. A comparative analysis of different treatments,
solutions and compatibility with observational bounds or detection perspectives
is made.Comment: LaTeX, 50 pages with 2 figures. Uses epsfig and psfra
Reconstruction of source location in a network of gravitational wave interferometric detectors
This paper deals with the reconstruction of the direction of a gravitational
wave source using the detection made by a network of interferometric detectors,
mainly the LIGO and Virgo detectors. We suppose that an event has been seen in
coincidence using a filter applied on the three detector data streams. Using
the arrival time (and its associated error) of the gravitational signal in each
detector, the direction of the source in the sky is computed using a chi^2
minimization technique. For reasonably large signals (SNR>4.5 in all
detectors), the mean angular error between the real location and the
reconstructed one is about 1 degree. We also investigate the effect of the
network geometry assuming the same angular response for all interferometric
detectors. It appears that the reconstruction quality is not uniform over the
sky and is degraded when the source approaches the plane defined by the three
detectors. Adding at least one other detector to the LIGO-Virgo network reduces
the blind regions and in the case of 6 detectors, a precision less than 1
degree on the source direction can be reached for 99% of the sky.Comment: Accepted in Phys. Rev.
Long term study of the seismic environment at LIGO
The LIGO experiment aims to detect and study gravitational waves using ground
based laser interferometry. A critical factor to the performance of the
interferometers, and a major consideration in the design of possible future
upgrades, is isolation of the interferometer optics from seismic noise. We
present the results of a detailed program of measurements of the seismic
environment surrounding the LIGO interferometers. We describe the experimental
configuration used to collect the data, which was acquired over a 613 day
period. The measurements focused on the frequency range 0.1-10 Hz, in which the
secondary microseismic peak and noise due to human activity in the vicinity of
the detectors was found to be particularly critical to interferometer
performance. We compare the statistical distribution of the data sets from the
two interferometer sites, construct amplitude spectral densities of seismic
noise amplitude fluctuations with periods of up to 3 months, and analyze the
data for any long term trends in the amplitude of seismic noise in this
critical frequency range.Comment: To be published in Classical and Quantum Gravity. 24 pages, 15
figure
Narrow-band search of continuous gravitational-wave signals from Crab and Vela pulsars in Virgo VSR4 data
In this paper we present the results of a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small mismatch between the gravitational-wave frequency and two times the star rotation frequency, inferred from measurement of the electromagnetic pulse rate, a range of 0.02 Hz around two times the star rotational frequency has been searched for both the pulsars. No evidence for a signal has been found and 95% confidence level upper limits have been computed assuming both that polarization parameters are completely unknown and that they are known with some uncertainty, as derived from x-ray observations of the pulsar wind torii. For Vela the upper limits are comparable to the spin-down limit, computed assuming that all the observed spin-down is due to the emission of gravitational waves. For Crab the upper limits are about a factor of 2 below the spin-down limit, and represent a significant improvement with respect to past analysis. This is the first time the spin-down limit is significantly overcome in a narrow-band search.Fil: Quiroga, Gonzalo Damián. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Relatividad y Gravitacion; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Maglione, Cesar German. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Relatividad y Gravitacion; ArgentinaFil: Reula, Oscar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Relatividad y Gravitacion; ArgentinaFil: Aasi, J.. California Institute of Technology; Estados UnidosFil: Abbot, B. P.. California Institute of Technology; Estados UnidosFil: Abbot, R.. California Institute of Technology; Estados UnidosFil: Abbot, T.. State University of Louisiana; Estados UnidosFil: Abernathy, M. R.. California Institute of Technology; Estados UnidosFil: Acernese, F.. Universita di Salerno; Italia. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Ackley, K.. University of Florida; Estados UnidosFil: Adams, C.. LIGO Livingston Observatory; Estados UnidosFil: Adams, T.. Universite de Savoie. Laboratoire d’Annecy-le-Vieux de Physique des Particules; Francia. Cardiff University; Reino UnidoFil: Adams, T.. Universite de Savoie. Laboratoire d’Annecy-le-Vieux de Physique des Particules; FranciaFil: Addesso, P.. University of Sannio at Benevento; ItaliaFil: Adhikar, R. X.. California Institute of Technology; Estados UnidosFil: Adya, V.. Max-Planck-Institut für Gravitationsphysik; AlemaniaFil: Affeldt, C.. Max-Planck-Institut für Gravitationsphysik; AlemaniaFil: Agathos, M.. Nikhef; Science Park; Países BajosFil: Agatsuma, K.. Nikhef; Science Park; Países BajosFil: Aggarwal, N.. Massachusetts Institute of Technology; Estados UnidosFil: Aguiar, O. D.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Ain, A.. Inter-University Centre for Astronomy and Astrophysics; IndiaFil: Ajith, P.. Tata Institute of Fundamental Research; IndiaFil: Alemic, A.. Syracuse University; Estados UnidosFil: Allen, B.. Max-Planck-Institut für Gravitationsphysik; Alemania. University of Wisconsin; Estados UnidosFil: Allocca, A.. Università degli Studi di Siena; Italia. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Amariutei, D.. University of Florida; Estados UnidosFil: Anderson, S. B.. California Institute of Technology; Estados UnidosFil: Anderson, W. G.. University of Wisconsin; Estados UnidosFil: Arai, K.. California Institute of Technology; Estados Unido
On the relation between effective supersymmetric actions in different dimensions
We make two remarks: (i) Renormalization of the effective charge in a
4--dimensional (supersymmetric) gauge theory is determined by the same graphs
and is rigidly connected to the renormalization of the metric on the moduli
space of the classical vacua of the corresponding reduced quantum mechanical
system. Supersymmetry provides constraints for possible modifications of the
metric, and this gives us a simple proof of nonrenormalization theorems for the
original 4-dimensional theory. (ii) We establish a nontrivial relationship
between the effective (0+1)-dimensional and (1+1)-dimensional Lagrangia (the
latter represent conventional
Kahlerian sigma models).Comment: 15 pages, 2 figure
Do Quarks Obey D-Brane Dynamics?
The potential between two D0-branes at rest is calculated to be a linear.
Also the potential between two fast decaying D0-branes is found in agreement
with phenomenological heavy-quark potentials.Comment: 7 pages, no figures, LaTe
Finding Z' bosons coupled preferentially to the third family at CERN LEP and the Fermilab Tevatron
Z' bosons that couple preferentially to the third generation fermions can
arise in models with extended weak (SU(2)xSU(2)) or hypercharge (U(1)xU(1))
gauge groups. We show that existing limits on quark-lepton compositeness set by
the LEP and Tevatron experiments translate into lower bounds of order a few
hundred GeV on the masses of these Z' bosons. Resonances of this mass can be
directly produced at the Tevatron. Accordingly, we explore in detail the limits
that can be set at Run II using the process p pbar -> Z' -> tau tau -> e mu. We
also comment on the possibility of using hadronically-decaying taus to improve
the limits.Comment: LaTeX2e, 24 pages (including title page), 13 figures; version 2:
corrected typographical errors and bad figure placement; version 3: added
references and updated introduction; version 4: changes to compensate for old
latex version on arXiv server; version 5: additional references, and embedded
fonts in eps files for PRD; version 6: corrected some minor typos to address
PRD referee's comment
Global structure of exact cosmological solutions in the brane world
We find the explicit coordinate transformation which links two exact
cosmological solutions of the brane world which have been recently discovered.
This means that both solutions are exactly the same with each other. One of two
solutions is described by the motion of a domain wall in the well-known
5-dimensional Schwarzshild-AdS spacetime. Hence, we can easily understand the
region covered by the coordinate used by another solution.Comment: Latex, 9 pages including 5 figures; references add, accepted for
publication in Physical Review
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