Thermodynamical Behaviour of Composite Stringy Black Holes

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 characterised by a dilaton which is constant near the horizon, whereas this suppression does not occur when the dilaton is non constant

The status of GEO 600

The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode

Data acquisition and detector characterization of GEO600

The data acquisition system of the gravitational wave detector GEO600 is recording the first data now. Data from detector subsystems and environmental channels are being acquired. The data acquisition system is described and first results from the detector characterization work are being presented. We analysed environmental influences on the detector to determine noise propagation through the detector. Long-term monitoring allowed us to see long-timescale drifts in subsystems

Characterization of the Virgo seismic environment

The Virgo gravitational wave detector is an interferometer (ITF) with 3 km arms located in Pisa, Italy. From July to October 2010, Virgo performed its third science run (VSR3) in coincidence with the LIGO detectors. Despite several techniques adopted to isolate the ITF from the environment, seismic noise remains an important issue for Virgo. Vibrations produced by the detector infrastructure (such as air conditioning units, water chillers/heaters, pumps) are found to affect Virgo''s sensitivity, with the main coupling mechanisms being through beam jitter and scattered light processes. The Advanced Virgo design seeks to reduce ITF couplings to environmental noise by having most vibration-sensitive components suspended and in vacuum, as well as muffle and relocate loud machines. During the months of June and July in 2010, a Guralp-3TD seismometer was stationed at various locations around the Virgo site hosting major infrastructure machines. Seismic data were examined using spectral and coherence analysis with seismic probes close to the detector. The primary aim of this study was to identify noisy machines which seismically affect the ITF environment and thus require mitigation attention. Analyzed machines are located at various distances from the experimental halls, ranging from 10 to 100 m. An attempt is made to measure the attenuation of emitted noise at the ITF and correlate it with the distance from the source and with seismic attenuation models in soil

Status of the Commissioning of the Virgo Interferometer

Long baseline optical interferometry is a promising technique for the detection of gravitational waves [1], [2], [3], [4]. The French-Italian detector Virgo is a Michelson interferometer with 3 km arms, equipped with high storage time Fabry-Perot cavities. In this kind of detectors, the passage of gravitational waves would be sensed as a differential length variation of the arms. After the end of the second Virgo Science Run, lasting from July 2009 to the beginning of January 2010, some important upgrades have been carried out; in particular, the mirrors of the Fabry-Perot cavities, which act as test masses of the detector, have been replaced by new ones with an higher reflectivity, which should increase by three times the finesse of the cavities; moreover the mirrors are now suspended by silica fibers in a monolithic assembly expected to significantly lower the thermal noise. Finally, the digital signal processing electronics and the global control system have been largely improved. We will present the status of the commissioning of the Virgo interferometer

The NoEMi (Noise Frequency Event Miner) framework

The data collected by a gravitational wave interferometer are inevitably affected by instrumental artefacts and environmental disturbances. In particular, for continuous gravitational wave (CW) studies it is important to detect narrow-band disturbances (the so-called "noise lines") during science runs, and to help scientists to identify and possibly remove or mitigate their sources. The NoEMi (Noise Frequency Event Miner) framework exploits some of the algorithms implemented for the CW search to identify, on a daily basis, the frequency lines observed in the Virgo science data and in a subset of the environmental sensors, looking for lines that match in frequency. A line tracker algorithm reconstructs the lines over time, and stores them in a database, which is made accesible via a web interface. We describe the workflow of NoEMi, providing examples of its use for the investigation of noise lines in past Virgo runs (VSR2, VSR3) and in the most recent run (VSR4)

Noise monitor tools and their application to Virgo data

The understanding of noise in interferometric gravitational wave detectors is fundamental in terms of both enabling prompt reactions in the mitigation of noise disturbances and in the establishment of appropriate data-cleaning strategies. Monitoring tools to perform online and offline noise analysis in areas such as transient signal detection, line identification algorithms and coherence are used to characterise the Virgo detector noise. In this paper, we describe the framework into which these tools are integrated - the Noise Monitor Application Programming Interface (NMAPI) - and provide examples of its application

Central heating radius of curvature correction (CHRoCC) for use in large scale gravitational wave interferometers

An asymmetry in radii of curvature of the mirrors in the arms of an interferometric gravitational-wave detector can degrade the performance of such a detector. In addition, the non-perfect mirror surface figures can excite higher order modes if the radii of curvature are close to higher order mode degeneracy. In this paper, we present a novel technique for changing the radii of curvature of arm cavity end mirrors by Central Heating Radius of Curvature Correction. This system was installed in the Virgo experiment in Cascina and proved to be an efficient, non-invasive solution with a large dynamic range. We present how the interferometer was tuned using such a system in order to obtain the best duty-cycles and sensitivity achieved with Virgo to date

Status of the Virgo project

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

The Virgo Interferometer For Gravitational Wave Detection

The Virgo interferometer for gravitational wave detection is described. During the commissioning phase that followed the first scientific data taking run an unprecedented sensitivity was obtained in the range 10-60 Hz. Since then an upgrade program has begun, with the aim of increasing the sensitivity, mainly through the introduction of fused silica wires to suspend mirrors and by increasing the Finesse of the Fabry-Perot cavities. Plans until the shutdown for the construction of the Advanced Virgo detector are given as well as the status of the upgrade