Table of contents

At GRG17 in Dublin in 2004, it was decided to hold GRG18 in Sydney in 2007. Every six years, the GRG conference (held every three years) and Amaldi meeting (held every two years) occur in the same year around July. This was to be the case in 2007. By mutual agreement of the International Society on General Relativity and Gravitation (ISGRG), which oversees the GR conferences and The Gravitational Wave International Committee (GWIC), which oversees the Amaldi meetings, it was decided to hold these two important conferences concurrently, for the first time, at the same venue, namely Sydney. At a time when the gravitational wave community was beginning to explore the possibility of searches to probe various aspects of the theory, the vision was to bring that community together with the community of gravitational theorists in order to better appreciate the work being done by both parties and to explore possibilities for future research using the mutual expertise.

The logistics of running two such large meetings concurrently were considerable. The format agreed upon by the ISGRG and GWIC was the following: common plenary sessions in the mornings from Monday to Friday; six parallel GR workshop sessions and an Amaldi session each afternoon from Monday to Friday (except Wednesday); a combined poster session on Wednesday; a full day of Amaldi sessions on the final day (Saturday). The scientific programme for GRG18 was overseen by a Scientific Organising Committee established by the ISGRG and chaired by Professor Sathyaprakash. The scientific programme for Amaldi7 was overseen by GWIC chaired by Professor Cerdonio.

One of the highlights of the conferences was the breadth and quality of the plenary programme put together by the scientific committees. Not only did these talks give an excellent snapshot of the entire field at this time, but they also explored the interfaces with other related fields, which proved of special interest to participants. We were given superb overviews of the state of the art of: observational handles on dark energy; collider physics experiments designed to probe cosmology; gravitational dynamics of large stellar systems; and the use of analogue condensed-matter systems in the laboratory to investigate black hole event horizons. In the more mainstream areas we were given timely reviews of: the Gravity Probe B and STEP missions; quasi-local black hole horizons and their applications; cosmic censorship; the spin foam model approach to quantum gravity; the causal dynamical triangulations approach to quantum gravity; superstring theory applied to questions in particle physics; the current status and prospects for gravitational wave astronomy; ground-based gravitational wave detection; and technological developments for the future LISA mission.

This issue is published as the proceedings of GRG18 and Amaldi7. It contains the overview articles by the plenary speakers, the summaries of each GRG18 workshop parallel session as provided by the workshop chairs, and the highlights of the Amaldi7 meeting as selected by the Amaldi7 chairs. Other Amaldi7 talks and posters will appear as articles in a refereed issue of the electronic Journal of Physics Conference Series. This CQG special issue and the related issue of JPCS will be electronically linked.

The conference organisers would like to acknowledge the financial support of: The Australian National University; IUPAP; The Australian Institute of Physics; BHP Billiton; The University of Western Australia; The University of New South Wales; The Institute of Physics; The Gravity Research Foundation; SGI; CosNet; The Australian Mathematical Sciences Institute; Springer; Duraduct; the New South Wales Government; The Australasian Society for General Relativity and Gravitation; the Mexican GR bid; the Centre for Precision Optics; The Anglo-Australian Observatory; Newspec; CSIRO; and The University of Melbourne.

We would like to thank the GRG18 Scientific Organising Committee, GWIC and the Local Organising Committee for all their hard work in putting together these very successful combined conferences, which attracted 520 participants. Many of the practical aspects of the organisation were handled by the event management company Conexion, and their professionalism, expertise and dedication were greatly appreciated. We would also like to thank the editorial staff at CQG, especially Eirini Messaritaki and Joseph Tennant, for their support and efficiency in preparing this issue. Finally, we would like to thank all the participants for their lively and colourful contributions to making these conferences a success.

The 7th Edoardo Amaldi Conference on Gravitational Waves was held on 8–14 July 2007, Sydney Convention and Exhibition Centre, Darling Harbour, Sydney, Australia.

A selection of papers, chosen by the conference organisers, are published here in a special issue of Classical and Quantum Gravity.

The bulk of the papers presented at the conference, after peer review, are published in Journal of Physics: Conference Series.

I review the observational evidence for dark energy, arguing that the large-scale structure observed at low redshift and in the cosmic microwave background offers a strong corroboration of the supernova Ia results. The angular scale of the acoustic oscillations in the cosmic microwave background strongly support a nearly flat universe, while many arguments from low-redshift cosmology support a matter density around 25% of the critical density. The observational constraints on the cosmological model have improved dramatically over the past decade. The coming decade will likely bring another two to three orders of magnitude in improvements in the data sets used for the study of dark energy.

Gravity Probe B (GP-B) is a landmark physics experiment in space designed to yield precise tests of two fundamental predictions of Einstein's theory of general relativity, the geodetic and frame-dragging effects, by means of cryogenic gyroscopes in Earth orbit. Launched on 20 April 2004, data collection began on 28 August 2004 and science operations were completed on 29 September 2005 upon liquid helium depletion. During the course of the experiment, two unexpected and mutually-reinforcing complications were discovered: (1) larger than expected 'misalignment' torques on the gyroscopes producing classical drifts larger than the relativity effects under study and (2) a damped polhode oscillation that complicated the calibration of the instrument's scale factor against the aberration of starlight. Steady progress through 2006 and 2007 established the methods for treating both problems; in particular, an extended effort from January 2007 on 'trapped flux mapping' led in August 2007 to a dramatic breakthrough, resulting in a factor of ∼20 reduction in data scatter. This paper reports results up to November 2007. Detailed investigation of a central 85-day segment of the data has yielded robust measurements of both relativity effects. Expansion to the complete science data set, along with anticipated improvements in modeling and in the treatment of systematic errors may be expected to yield a 3–6% determination of the frame-dragging effect.

This year, the Large Hadron Collider (LHC) will begin colliding protons at energies nearly an order of magnitude beyond the current frontier. The LHC will, of course, provide unprecedented opportunities to discover new particle physics. Less well-known, however, is that the LHC may also provide insights about gravity and the early universe. I review some of these connections, focusing on the topics of dark matter and dark energy, and highlight outstanding prospects for breakthroughs at the interface of particle physics and cosmology.

In this paper, we give an overview of the main techniques developed in the context of background independent gravity in order to tackle the problem of the dynamics. We briefly introduce loop quantum gravity, highlighting some of its achievements and then present spin foam models which allows the construction of dynamical transition amplitudes between loop quantum gravity states. We then present three types of applications of these sets of ideas. First, we describe how the coupling to matter can be achieved in this context and how this has allowed us to show that in 2+1 the effective geometry created by quantum gravity is non-commutative. Then we present how we can extract information of the graviton propagator from spin foam amplitudes and finally we emphasize some recent application to quantum cosmology.

The traditional description of black holes in terms of event horizons is inadequate for many physical applications, especially when studying black holes in non-stationary spacetimes. In these cases, it is often more useful to use the quasi-local notions of trapped and marginally trapped surfaces, which lead naturally to the framework of trapping, isolated and dynamical horizons. This framework allows us to analyze diverse facets of black holes in a unified manner and to significantly generalize several results in black hole physics. It also leads to a number of applications in mathematical general relativity, numerical relativity, astrophysics and quantum gravity. In this short review, I will discuss the basic ideas and recent developments in this framework, and summarize some of its applications with an emphasis on numerical relativity.

Is there an approach to quantum gravity which is conceptually simple, relies on very few fundamental physical principles and ingredients, emphasizes geometric (as opposed to algebraic) properties, comes with a definite numerical approximation scheme, and produces robust results, which go beyond showing mere internal consistency of the formalism? The answer is a resounding yes: it is the attempt to construct a nonperturbative theory of quantum gravity, valid on all scales, with the technique of so-called causal dynamical triangulations. Despite its conceptual simplicity, the results obtained up to now are far from trivial. Most remarkable at this stage is perhaps the fully dynamical emergence of a classical background (and solution to the Einstein equations) from a nonperturbative sum over geometries, without putting in any preferred geometric background at the outset. In addition, there is concrete evidence for the presence of a fractal spacetime foam on Planckian distance scales. The availability of a computational framework provides built-in reality checks of the approach, whose importance can hardly be overestimated.

Internal dynamical evolution can drive stellar systems into states of high central density. For many star clusters and galactic nuclei, the time scale on which this occurs is significantly less than the age of the universe. As a result, such systems are expected to be sites of frequent interactions among stars, binary systems and stellar remnants, making them efficient factories for the production of compact binaries, intermediate-mass black holes and other interesting and eminently observable astrophysical exotica. We describe some elements of the competition among stellar dynamics, stellar evolution and other mechanisms to control the dynamics of stellar systems, and discuss briefly the techniques by which these systems are modeled and studied. Particular emphasis is placed on pathways leading to massive black holes in present-day globular clusters and other potentially detectable sources of gravitational radiation.

In recent years, experiments have discovered an exotic new state of matter known as the strongly coupled quark–gluon plasma (sQGP). At present, it seems that standard theoretical tools, such as perturbation theory and lattice gauge theory, are poorly suited to understand this new phase. However, recent progress in superstring theory has provided us with a theoretical laboratory for studying very similar systems of strongly interacting hot non-Abelian plasmas. This surprising new perspective extracts the fluid properties of the sQGP from physical processes in a black hole spacetime. Hence we may find the answers to difficult particle physics questions about the sQGP from straightforward calculations in classical general relativity.

I will review the most recent and interesting results from gravitational-wave detection experiments, concentrating on recent results from the LIGO Scientific Collaboration (LSC). I will outline the methodologies utilized in the searches, explain what can be said in the case of a null result and what quantities may be constrained. I will compare these results with prior expectations and discuss their significance. As I go along I will outline the prospects for future improvements.

In 1952, Yvonne Choquet-Bruhat demonstrated that it makes sense to consider Einstein's vacuum equations from an initial value point of view; given initial data, there is a globally hyperbolic development. Since there are many developments, one does, however, not obtain uniqueness. This was remedied in 1969 when Choquet-Bruhat and Robert Geroch demonstrated that there is a unique maximal globally hyperbolic development (MGHD). Unfortunately, there are examples of initial data for which the MGHD is extendible, and, what is worse, extendible in inequivalent ways. Thus it is not possible to predict what spacetime one is in simply by looking at initial data and, in this sense, Einstein's equations are not deterministic. Since the examples exhibiting this behaviour are rather special, it is natural to conjecture that for generic initial data, the MGHD is inextendible. This conjecture is referred to as the strong cosmic censorship conjecture and is of central importance in mathematical relativity. In this paper, we shall describe this conjecture in detail, as well as its resolution in the special case of T³-Gowdy spacetimes.

The concept of a horizon known from general relativity describes the loss of causal connection and can be applied to non-gravitational scenarios such as out-of-equilibrium condensed-matter systems in the laboratory. This analogy facilitates the identification and theoretical study (e.g., regarding the trans-Planckian problem) and possibly the experimental verification of 'exotic' effects known from gravity and cosmology, such as Hawking radiation. Furthermore, it yields a unified description and better understanding of non-equilibrium phenomena in condensed-matter systems and their universal features. By means of several examples including general fluid flows, expanding Bose–Einstein condensates and dynamical quantum phase transitions, the concepts of event, particle and apparent horizons will be discussed together with the resulting quantum effects.

The laser interferometer space antenna will be the first space-based laser interferometric gravitational wave detector. This paper provides a brief introduction to the LISA mission and science goals, highlighting the differences from ground-based detectors. A tutorial of the LISA measurement concept is presented focusing on the LISA interferometry with a summary of laser frequency noise cancellation and clock noise removal schemes.

In the past three years, the first generation of large gravitational-wave interferometers has begun operation near their design sensitivities, taking up the mantle from the bar detectors that pioneered the search for the first direct detection of gravitational waves. Even as the current ground-based interferometers were reaching their design sensitivities, plans were being laid for the future. Advances in technology and lessons learned from the first generation devices have pointed the way to an order of magnitude improvement in sensitivity, as well as expanded frequency ranges and the capability to tailor the sensitivity band to address particular astrophysical sources. Advanced cryogenic acoustic detectors, the successors to the current bar detectors, are being researched and may play a role in the future, particularly at the higher frequencies. One of the most important trends is the growing international cooperation aimed at building a truly global network. In this paper, I survey the state of the various detectors as of mid-2007, and outline the prospects for the future.

I report on the communications and posters presented on exact solutions and their interpretation at the GRG18 Conference, Sydney.

Submissions on twistor theory concerned possible descriptions of the collapse of the wavefunction, recent developments arising from twistor-string theory, applications to conventional string theory, and applications to four-dimensional geometry. Those on connection variables and other complex methods concerned the definition of conserved quantities, the canonical formalism for general relativity without using the metric, quasi-local definitions of mass and spectral properties of two-surfaces.

In this report I will give a summary of some of the main topics covered in session A3, mathematical studies of the field equations, at GRG18, Sydney. Unfortunately, due to length constraints, some of the topics covered at the session will be very briefly mentioned or left out altogether. The summary is mainly based on extended abstracts submitted by the speakers and some of those who presented posters at the session. I would like to thank all participants for their contributions and help with this summary.

More than 50 abstracts were submitted to the A4 session on alternative theories of gravity at the GRG18 conference. About 30 of them were scheduled as oral presentations that we summarize below. We do not intend to give a critical review, but rather pointers to the corresponding papers. The main topics were: (i) brane models both from the mathematical and the phenomenological viewpoints; (ii) Einstein–Gauss–Bonnet gravity in higher dimensions or coupled to a scalar field; (iii) modified Newtonian dynamics (MOND); (iv) scalar–tensor and f(R) theories; (v) alternative models involving Lorentz violations, noncommutative spacetimes or Chern–Simons corrections.

The B1 parallel session on relativistic astrophysics at GR-18 contained an impressive variety of papers on key astronomical topics. Many of the papers involved sophisticated applications of general relativity and mathematical physics to areas of current interest in astronomy. The development of a number of the results and ideas presented at GR-18 will have an important bearing on future astronomical theories and observation.

The numerical relativity session at GR18 was dominated by physics results on binary black hole mergers. Several groups can now simulate these from a time when the post-Newtonian equations of motion are still applicable, through several orbits and the merger to the ringdown phase, obtaining plausible gravitational waves at infinity, and showing some evidence of convergence with resolution. The results of different groups roughly agree. This new-won confidence has been used by these groups to begin mapping out the (finite dimensional) initial data space of the problem, with a particular focus on the effect of black hole spins, and the acceleration by gravitational wave recoil to hundreds of km s⁻¹ of the final merged black hole. Other work was presented on a variety of topics, such as evolutions with matter, extreme mass ratio inspirals and technical issues such as gauge choices.

The paper summarizes the parallel session B3 analytic approximations, perturbation methods and their applications of the GR18 conference. The talks in the session reported notably recent advances in black hole perturbations and post-Newtonian approximations as applied to sources of gravitational waves.

In session B4—early universe, pre-big bang, etc—there were ten talks. Among them were three invited talks by Vilenkin, Ashtekar and Kodama, which highlighted the session. Here I summarize the session. I also present my personal point of view on some of the issues discussed in the session.

I summarize talks from parallel sessions (B5 and B6) of the 18th International Conference on General Relativity and Gravitation (GRG18). These talks are primarily related to dark energy and the cosmological constant, but also cover a session related to the CMB, large scale structure and gravitational lenses.

The fact that gravity is a metric theory follows from the Einstein equivalence principle. This principle consists of (i) the universality of free fall, (ii) the universality of the gravitational redshift and (iii) the local validity of Lorentz invariance. Many experiments searching for deviations from standard general relativity test the various aspects of the Einstein equivalence principle. Here we report on experiments covering the whole Einstein equivalence principle. Until now all experiments have been in agreement with the Einstein equivalence principle. As a consequence, gravity has to be described by a metric theory. Any metric theory of gravity leads to effects such as perihelion shift, deflection of light, gravitational redshift, gravitational time delay, Lense–Thirring effect, Schiff effect, etc. A particular theory of that sort is Einstein's general relativity. For weak gravitational fields which are asymptotically flat any deviation from Einstein's general relativity can be parametrized by a few constants, the PPN parameters. Many astrophysical observations and space experiments are devoted to a better measurement of the effects and, thus, of the PPN parameters. It is clear that gravity is best tested for intermediate ranges, that is, for distances between 1 m and several astronomical units. It is highly interesting to push forward our domain of experience and to strengthen the experimental foundation of gravity also beyond these scales. This point is underlined by the fact that many quantum gravity and unification-inspired theories suggest deviation from the standard laws of gravity at very small or very large scales. In this session summary we briefly outline the status and report on the talks presented in session C1 about experimental gravitation.

The talks presented in the parallel session on quantum aspects of black holes at the 18th conference on general relativity and gravitation in Sydney, Australia are summarized below.

This is a summary of talks about quantum aspects of cosmology. Topics involve the properties of quantum matter fields on an expanding spacetime as well as issues in the quantization of gravity itself. This session had three parts, one of which was in a joint session with quantum aspects of black holes (D1) and other quantum aspects (D3). The first block of talks was related to quantum aspects of field theories on a classical spacetime (with possible back-reaction), while the second block dealt in several ways with quantizations of gravity itself. The two talks in the combined session discussed issues in quantum theory on de Sitter space and will therefore be included here in the summary of the first block. For each talk, a reference is given for further details.

I briefly summarize concurrent session D3, 'Other Quantum Aspects,' held at the GR18 meeting held in Sydney in July, 2007.

This is an attempt to summarize (not exhaustively) some of the recent developments in the field of analogue gravity, which were reported on at the GRG18 in Sydney.

The data collected during 2005 by the resonant bar Explorer are divided into segments and incoherently summed in order to perform an all-sky search for periodic gravitational wave signals. The parameter space of the search spanned about 40 Hz in frequency, over 23 927 positions in the sky. Neither source orbital corrections nor spindown parameters have been included, with the result that the search was sensitive to isolated neutron stars with a frequency drift less than 6 × 10⁻¹¹ Hz s⁻¹. No gravitational wave candidates have been found by means of the present analysis, which led to a best upper limit of 3.1 × 10⁻²³ for the dimensionless strain amplitude.

We describe a coherent network algorithm for detection and reconstruction of gravitational wave bursts. The algorithm works for two and more arbitrarily aligned detectors and can be used for both all-sky and triggered burst searches. We describe the main components of the algorithm, including the time-frequency analysis in a wavelet domain, construction of the likelihood time-frequency maps, and identification and selection of burst events.

The Laser Interferometer Gravitational Wave Observatory (LIGO) operates a 40m prototype interferometer on the Caltech campus. The primary mission of the prototype is to serve as an experimental testbed for upgrades to the LIGO interferometers and for gaining experience with advanced interferometric techniques, including detuned resonant sideband extraction (i.e. signal recycling) and dc readout (optical homodyne detection). The former technique will be employed in Advanced LIGO, and the latter in both Enhanced and Advanced LIGO. Using dc readout for gravitational wave signal extraction has several technical advantages, including reduced laser and oscillator noise couplings as well as reduced shot noise, when compared to the traditional rf readout technique (optical heterodyne detection) currently in use in large-scale ground-based interferometric gravitational wave detectors. The Caltech 40m laboratory is currently prototyping a dc readout system for a fully suspended interferometric gravitational wave detector. The system includes an optical filter cavity at the interferometer's output port, and the associated controls and optics to ensure that the filter cavity is optimally coupled to the interferometer. We present the results of measurements to characterize noise couplings in rf and dc readout using this system.

We have demonstrated displacement- and frequency-noise-free laser interferometry (DFI) by partially implementing a recently proposed optical configuration using bi-directional Mach–Zehnder interferometers (MZIs). This partial implementation, the minimum necessary to be called DFI, has confirmed the essential feature of DFI: the combination of two MZI signals can be carried out in a way that cancels the displacement noise of the mirrors and beam splitters while maintaining gravitational-wave signals. The attained maximum displacement noise suppression was 45 dB.

Pulsar timing experiments are reaching sufficient sensitivity to detect a postulated stochastic gravitational wave background generated by merging supermassive black hole systems in the cores of galaxies. We describe the techniques behind the pulsar timing detection method, provide current upper bounds on the amplitude of any gravitational wave background, describe theoretical models predicting the existence of such a background and highlight new techniques for providing a statistically rigorous detection of the background.

While the inspiral and ring-down stages of the binary black-hole coalescence are well modelled by analytical approximation methods in general relativity, the recent progress in numerical relativity has enabled us to compute accurate waveforms from the merger stage also. This has an important impact on the search for gravitational waves from binary black holes. 'Complete' binary black-hole waveforms can now be produced by matching post-Newtonian waveforms with those computed by numerical relativity, which can be parametrized to produce analytical waveform templates. The 'complete' waveforms can also be used to estimate the efficiency of different search methods aiming to detect signals from black-hole coalescences. This paper summarizes some recent efforts in this direction.

LISA Pathfinder (formerly known as SMART-2) is an ESA mission designed to pave the way for the joint ESA/NASA Laser Interferometer Space Antenna (LISA) mission by testing in-flight the critical technologies required for space-borne gravitational wave detection; it will put two test masses in a near-perfect gravitational free fall, and control and measure their motion with an unprecedented accuracy. This is achieved through technology comprising inertial sensors, high-precision laser metrology, drag-free control and an ultra-precise micro-Newton propulsion system. The LISA Pathfinder mission is now in Phase C/D—the Implementation Phase, and is due to be launched in 2010, with results on the performance of the system being available within 6 months thereafter.

We present a preliminary study of the multipolar structure of gravitational radiation from spinning black hole binary mergers. We consider three different spinning binary configurations: (1) one 'hang-up' run, where the black holes have equal masses and large spins initially aligned with the orbital angular momentum; (2) seven 'spin-flip' runs, where the holes have a mass ratio q ≡ M₁/M₂ = 4, the spins are anti-aligned with the orbital angular momentum, and the initial Kerr parameters of the holes j₁ = j₂ = j_i (where j ≡ J/M²) are fine-tuned to produce a Schwarzschild remnant after merger; (3) three 'super-kick' runs where the mass ratio q = 1, 2, 4 and the spins of the two holes are initially located on the orbital plane, pointing in opposite directions. For all of these simulations we compute the multipolar energy distribution and the Kerr parameter of the final hole. For the hang-up run, we show that including leading-order spin–orbit and spin–spin terms in a multipolar decomposition of the post-Newtonian waveforms improves agreement with the numerical simulation.

TAMA300 has been upgraded to improve the sensitivity at low frequencies after the last observation run in 2004. To avoid the noise caused by seismic activities, we installed a new seismic isolation system—the TAMA seismic attenuation system (SAS). Four SAS towers for the test-mass mirrors were sequentially installed from 2005 to 2006. The recycled Fabry–Perot Michelson interferometer was successfully locked with the SAS. We confirmed the reduction of both length and angular fluctuations at frequencies higher than 1 Hz owing to the SAS.

The Mock LISA data challenges are a program to demonstrate LISA data-analysis capabilities and to encourage their development. Each round of challenges consists of several data sets containing simulated instrument noise and gravitational waves from sources of undisclosed parameters. Participants are asked to analyze the data sets and report the maximum information about the source parameters. The challenges are being released in rounds of increasing complexity and realism: here we present the results of Challenge 2, issued in Jan 2007, which successfully demonstrated the recovery of signals from nonspinning supermassive-black-hole binaries with optimal SNRs between ∼10 and 2000, from ∼20 000 overlapping galactic white-dwarf binaries (among a realistically distributed population of 26 million), and from the extreme-mass-ratio inspirals of compact objects into central galactic black holes with optimal SNRs ∼100.

We develop a Bayesian treatment of the problem of detecting unmodelled gravitational wave bursts using the new global network of interferometric detectors. We also compare this Bayesian treatment with existing coherent methods, and demonstrate that the existing methods make implicit assumptions on the distribution of signals that make them sub-optimal for realistic signal populations.

We present a coincidence search method for astronomical events using gravitational wave detectors in conjunction with other astronomical observations. We illustrate our method for the specific case of the LIGO gravitational wave detector and the IceCube neutrino detector. LIGO trigger events and IceCube events which occur within a given time window are selected as time-coincident events. Then the spatial overlap of the reconstructed event directions is evaluated using an unbinned maximum likelihood method. Our method was tested with Monte Carlo simulations based on realistic LIGO and IceCube event distributions. We estimated a typical false alarm rate for the analysis to be 1 event per 435 years. This is significantly smaller than the false alarm rates of the individual detectors.

Second generation gravitational wave detectors require high power lasers with more than 100 W of output power and with very low temporal and spatial fluctuations. To achieve the demanding stability levels required, low noise techniques and adequate control actuators have to be part of the high power laser design. In addition feedback control and passive noise filtering is used to reduce the fluctuations in the so-called prestabilized laser system (PSL). In this paper, we discuss the design of a 200 W PSL which is under development for the Advanced LIGO gravitational wave detector and will present the first results. The PSL noise requirements for advanced gravitational wave detectors will be discussed in general and the stabilization scheme proposed for the Advanced LIGO PSL will be described.

All three LIGO gravitational wave detectors have reached their design sensitivities. A sky-averaged detection range (SNR > 8) of more than 15 Mpc for gravitational waves emitted from inspiral binary neutron stars with masses of 1.4 M_⊙ has been achieved with the two 4 km instruments. The fifth LIGO science run started in November 2005 and ended in September 2007. A full year of triple coincidence data has been acquired. The duty cycle of a single instrument was between 66% and 79%. Results from previous science runs are presented.

Here we present a status report of the first spherical antenna project equipped with a set of parametric transducers for gravitational detection. The Mario Schenberg, as it is called, started its commissioning phase at the Physics Institute of the University of São Paulo, in September 2006, under the full support of FAPESP. We have been testing the three preliminary parametric transducer systems in order to prepare the detector for the next cryogenic run, when it will be calibrated. We are also developing sapphire oscillators that will replace the current ones thereby providing better performance. We also plan to install eight transducers in the near future, six of which are of the two-mode type and arranged according to the truncated icosahedron configuration. The other two, which will be placed close to the sphere equator, will be mechanically non-resonant. In doing so, we want to verify that if the Schenberg antenna can become a wideband gravitational wave detector through the use of an ultra-high sensitivity non-resonant transducer constructed using the recent achievements of nanotechnology.

The GEO 600 gravitational wave detector located near Hannover in Germany is part of the LSC network of gravitational wave observatories. Since January 2006 the GEO 600 detector has participated in the S5 LSC science run and acquired sensitive and well-characterized science data with a high duty cycle. Until 1 October 2007, 415 days of science data with an average peak sensitivity of better than 3 × 10⁻²² Hz^−1/2 have been collected. In this paper, we give a brief overview of GEO 600 and describe activities in the period between January 2006 and October 2007. Plans for the near and medium future are briefly discussed.

We investigate methods to estimate the parameters of the gravitational-wave signal from a spinning neutron star using Fourier-transformed segments of the strain response from an interferometric detector. Estimating the parameters from the power, we find generalizations of the PowerFlux method. Using simulated elliptically polarized signals injected into Gaussian noise, we apply the generalized methods to estimate the squared amplitudes of the plus and cross polarizations (and, in the most general case, the polarization angle), and test the relative detection efficiencies of the various methods.

The Virgo detector has now finished its first science run; a science mode duty cycle of more than 80% and a 4.5 Mpc horizon distance for binary neutron star inspiral sources were achieved. Commissioning breaks were organized during the run which permitted improvement of the sensitivity and the robustness of the interferometer against environmental perturbations like bad weather and earthquakes. The post-run commissioning phase has now started, with the goal of preparing the next upgrade step of the detector, Virgo+.

We present a method to search for transient gravitational waves using a network of detectors with different spectral and directional sensitivities: the interferometer Virgo and the bar detector AURIGA. The data analysis method is based on the measurements of the correlated energy in the network by means of a weighted cross-correlation. To limit the computational load, this coherent analysis step is performed around time–frequency coincident triggers selected by an excess power event trigger generator tuned at low thresholds. The final selection of gravitational wave candidates is performed by a combined cut on the correlated energy and on the significance as measured by the event trigger generator. The method has been tested on one day of data of AURIGA and Virgo during September 2005. The outcomes are compared to the results of a stand-alone time–frequency coincidence search. We discuss the advantages and the limits of this approach, in view of a possible future joint search between AURIGA and one interferometric detector.

We present a study of the gravitational waveforms from a series of spinning, equal-mass black hole binaries focusing on the harmonic content of the waves and the contribution of the individual harmonics to the signal-to-noise ratio. The gravitational waves were produced from two series of evolutions with black holes of initial spins equal in magnitude and anti-aligned with each other. In one series the magnitude of the spin is varied; while in the second, the initial angle between the black hole spins and the orbital angular momentum varies. We also conduct a preliminary investigation into using these waveforms as templates for detecting spinning binary black holes. Since these runs are relativity short, containing about two to three orbits, merger and ringdown, we limit our study to systems of total mass ⩾50M_⊙. This choice ensures that our waveforms are present in the ground-based detector band without needing addition gravitational-wave cycles. We find that while the mode contribution to the signal-to-noise ratio varies with the initial angle, the total mass of the system caused greater variations in the match.

The two cryogenic resonant bar detectors of the ROG Collaboration, EXPLORER and NAUTILUS, have been taking data continuously with a high duty cycle for several years. We report here on the status of recent analysis of the data and in particular on the results of the burst searches in the year 2004.

Some of the prime targets for interferometric gravitational wave detectors, such as LIGO and VIRGO, are deformed rotating neutron stars, both isolated and in accreting systems. I will focus on deformations due to strong interior magnetic fields and on crustal deformations and I shall present a perturbative formalism to calculate the shape of the star in both these cases. I shall discuss the implications for the detection of sources by LIGO and VIRGO, especially for the case of LMXBs, in which gravitational waves may be playing an important role. Modelling these gravitational wave emission mechanisms is, in fact, an important issue both for gravitational wave data analysis and for astrophysics as gravitational wave observations may also allow us to constrain accretion and stellar magnetic field models. I will also consider deformations of a solid core and discuss how, in this case, LIGO may be used to investigate an interesting region of QCD parameter space.

Over the last year, the NASA half of the joint LISA project has focused its efforts on responding to a major review, and advancing the formulation and technology development of the mission. The NAS/NRC Beyond Einstein program assessment review will be described, including the outcome. The basis of the LISA science requirements has changed from detection determined by integrated signal-to-noise ratio to observation determined by uncertainty in the estimation of astrophysical source parameters. The NASA team has further defined the spacecraft bus design, participated in many design trade studies and advanced the requirements flow down and the associated current best estimates of performance. Recent progress in technology development is also summarized.

In gravitational-wave detection, special emphasis is put onto searches that focus on cosmic events detected by other types of astrophysical observatories. The astrophysical triggers, e.g. from γ-ray and x-ray satellites, optical telescopes and neutrino observatories, provide a trigger time for analyzing gravitational-wave data coincident with the event. In certain cases the expected frequency range, source energetics, directional and progenitor information are also available. Beyond allowing the recognition of gravitational waveforms with amplitudes closer to the noise floor of the detector, these triggered searches should also lead to rich science results even before the onset of Advanced LIGO. In this paper we provide a broad review of LIGO's astrophysically triggered searches and the sources they target.