Massive black hole binary systems, with masses in the range ∼104–1010M⊙, are among the primary sources of gravitational waves in the frequency window ∼10−9–0.1 Hz. Pulsar Timing Arrays (PTAs) and the ...Laser Interferometer Space Antenna (LISA) are the observational means by which we will be able to observe gravitational radiation from these systems. We carry out a systematic study of the generation of the stochastic gravitational-wave background from the cosmic population of massive black hole binaries. We consider a wide variety of assembly scenarios and we estimate the range of signal strength in the frequency band accessible to PTAs. We show that regardless of the specific model of massive black hole binaries formation and evolution, the characteristic amplitude hc of the gravitational-wave stochastic background at 10−8 Hz varies by less than a factor of 2. However, taking into account the uncertainties surrounding the actual key model parameters, the amplitude lies in the interval hc(f= 10−8Hz) ≈ 5 × 10−16–8 × 10−15. The most optimistic predictions place the signal level at a factor of ≈3 below the current sensitivity of PTAs, but within the detection range of the complete Parkes PTA for a wide variety of models, and of the future Square-Kilometer Array PTA for all the models considered here. We also show that at frequencies ≳10−8 Hz, the frequency dependency of the generated background follows a power law significantly steeper than hc∝f−2/3, which has been considered so far; the value of the spectral index depends on the actual assembly scenario and provides therefore an additional opportunity to extract astrophysical information about the cosmic population of massive black holes. Finally, we show that LISA observations of individual resolvable massive black hole binaries are complementary and orthogonal to PTA observations of a stochastic background from the whole population in the Universe. In fact, the detection of gravitational radiation in both frequency windows will enable us to fully characterize the cosmic history of massive black holes.
Status of the Virgo project Accadia, T; Acernese, F; Antonucci, F ...
Classical and quantum gravity,
06/2011, Letnik:
28, Številka:
11
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
We describe the present state and future evolution of the Virgo gravitational wave detector, realized by the Virgo Collaboration at the European Gravitational Observatory, in Cascina near Pisa in ...Italy. We summarize basic principles of the operation and the design features of the Virgo detector. We present the sensitivity evolution due to a series of intermediate upgrades called Virgo+ which is being completed this year and includes new monolithic suspensions. We describe the present scientific potential of the detector. Finally we discuss the plans for the second generation of the detector, called Advanced Virgo, introducing its new features, the expected sensitivity evolution and the scientific potential.
Status of the GEO600 detector Lück, H; Hewitson, M; Ajith, P ...
Classical and quantum gravity,
04/2006, Letnik:
23, Številka:
8
Journal Article, Conference Proceeding
Large gravitational wave interferometric detectors, like Virgo and LIGO, demonstrated the capability to reach their design sensitivity, but to transform these machines into an effective observational ...instrument for gravitational wave astronomy a large improvement in sensitivity is required. Advanced detectors in the near future and third-generation observatories in more than one decade will open the possibility to perform gravitational wave astronomical observations from the Earth. An overview of the possible science reaches and the technological progress needed to realize a third-generation observatory are discussed in this paper. The status of the project Einstein Telescope (ET), a design study of a third-generation gravitational wave observatory, will be reported.
We study the thermodynamical and geometrical behaviour of the black holes that arise as solutions of the heterotic string action. We discuss the near-horizon scaling behaviour of the solutions that ...are described by two-dimensional Anti-de Sitter space (
AdS
2). We find that finite-energy excitations of
AdS
2 are suppressed only for scaling limits characterized by a dilaton constant near the horizon, whereas this suppression does not occur when the dilaton is non-constant.
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