118457757
Towards a generic test of the strong field dynamics of general relativity using compact binary coalescence
Coalescences of binary neutron stars and/or black holes are amongst the most likely gravitational-wave signals to be observed in ground based interferometric detectors. Apart from the astrophysical importance of their detection, they will also provide us with our very first empirical access to the genuinely strong-field dynamics of General Relativity (GR). We present a new framework based on Bayesian model selection aimed at detecting deviations from GR, subject to the constraints of the Advanced Virgo and LIGO detectors. The method tests the consistency of coefficients appearing in the waveform with the predictions made by GR, without relying on any specific alternative theory of gravity. The framework is suitable for low signal-to-noise ratio events through the construction of multiple subtests, most of which involve only a limited number of coefficients. It also naturally allows for the combination of information from multiple sources to increase one's confidence in GR or a violation thereof. We expect it to be capable of finding a wide range of possible deviations from GR, including ones which in principle cannot be accommodated by the model waveforms, on condition that the induced change in phase at frequencies where the detectors are the most sensitive is comparable to the effect of a few percent change in one or more of the low-order post-Newtonian phase coefficients. In principle the framework can be used with any GR waveform approximant, with arbitrary parameterized deformations, to serve as model waveforms. In order to illustrate the workings of the method, we perform a range of numerical experiments in which simulated gravitational waves modeled in the restricted post-Newtonian, stationary phase approximation are added to Gaussian and stationary noise that follows the expected Advanced LIGO/Virgo noise curves.
17415632
Approximate solutions in General Relativity via deformation of embeddings
A systematic study of deformations of four-dimensional Einsteinian space-times embedded in a pseudo-Euclidean space E N of higher dimension is presented. Infinitesimal deformations, seen as vector fields in E N , can be divided in two parts, tangent to the embedded hypersurface and orthogonal to it; only the second ones are relevant, the tangent ones being equivalent to coordinate transformations in the embedded manifold. The geometrical quantities can be then expressed in terms of embedding functions z A and their infinitesimal deformations v A z A → ˜ z A = z A + e v A . The deformations are called Einsteinian if they keep Einstein equations satisfied up to a given order in e. The system so obtained is then analyzed in particular in the case of the Schwarzschild metric taken as the starting point, and some solutions of the first-order deformation of Einstein’s equations are found. We discuss also second and third order deformations leading to wave-like solutions and to the departure from spherical symmetry towards an axial one (the approximate Kerr solution) 1
118385730
Testing general relativity using gravitational waves from binary neutron stars: Effect of spins
We present a Bayesian data analysis pipeline for testing GR using gravitational wave signals from coalescing compact binaries, and in particular binary neutron stars. In this study, we investigate its performance when sources with spins are taken into account.
118465419
Parameter estimation from gravitational waves generated by nonspinning binary black holes with laser interferometers: Beyond the Fisher information
In this paper we apply to gravitational waves from nonspinning binary systems a recently introduced frequentist methodology to calculate analytically the error for a maximum likelihood estimate of physical parameters. While existing literature focuses on using the Cramer Rao Lower bound and Monte Carlo simulations, we use a power expansion of the bias and covariance in inverse powers of the signal to noise ratio. The use of higher order derivatives of the likelihood function in the expansions makes the prediction also sensitive to the secondary lobes of the maximum likelihood estimate probability distribution. We discuss conditions for validity of the Cramer Rao Lower bound and predict new features in regions of the parameter space currently not explored. For example, we see how the bias can become the most important contributor to the parameters' errors for high mass systems (200M(circle dot) and above).
23581346
Demonstrating the feasibility of probing the neutron-star equation of state with second-generation gravitational-wave detectors.
Fisher matrix and related studies have suggested that, with second-generation gravitational-wave detectors, it may be possible to infer the equation of state of neutron stars using tidal effects in a binary inspiral. Here, we present the first fully Bayesian investigation of this problem. We simulate a realistic data analysis setting by performing a series of numerical experiments of binary neutron-star signals hidden in detector noise, assuming the projected final design sensitivity of the Advanced LIGO-Virgo network. With an astrophysical distribution of events (in particular, uniform in comoving volume), we find that only a few tens of detections will be required to arrive at strong constraints, even for some of the softest equations of state in the literature. Thus, direct gravitational-wave detection will provide a unique probe of neutron-star structure.
117102512
Towards an Ultracryogenic Bar Observatory for Gravitational Wave Bursts
84846704
LISA Pathfinder
M Armanoa, H Audleyb, J Bairdc, P Binetruy d,∗, M Bornb, D Bortoluzzie, E Castellif , A Cavallerif , A Cesarinig , A M Cruiseh, K Danzmannb, M de Deus Silvaa, I Diepholzb, G Dixonh, R Dolesif , L Ferraiolii, V Ferronif , E D Fitzsimonsj , M Freschia, L Gesak, F Gibertf , D Giardinii, R Giusterif , C Grimanig , J Grzymischl, I Harrisonm, G Heinzelb, M Hewitsonb, D Hollingtonc, D Hoylandh, M Huellerf , H Inchauspéd, O Jennrichl, P Jetzern, N Karnesisb, B Kauneb, N Korsakovao, C J Killowo, J A Lobok,†, I Llorok, L Liuf , J P López-Zaragozak, R Maarschalkerweerdm, D Mancei N Meshskari, V Mart́ınk, L Martin-Poloa, J Martinod, F Martin-Porquerasa, I Mateosk, P W McNamaral, J Mendesm, L Mendesa, M Nofrariask, S Paczkowskib?, M Perreur-Lloydo, A Petiteaud, P Pivatof , E Plagnold, J Ramos-Castrop, J Reicheb, D I Robertsono, F Rivask, G Russanof , J Slutskyq , C F Sopuertak, T Sumnerc, D Texiera, J I Thorpeq , D Vetrugnof , S Vitalef , G Wannerb, H Wardo, P Wassc,r, W J Weberf , L Wisselb, A Wittchenb, and P Zweifeli a European Space Astronomy Centre, European Space Agency, Villanueva de la Cañada, 28692 Madrid, Spain
55218371
Brownian force noise from molecular collisions and the sensitivity of advanced gravitational wave observatories
We present an analysis of Brownian force noise from residual gas damping of reference test masses as a fundamental sensitivity limit in small force experiments. The resulting acceleration noise increases significantly when the distance of the test mass to the surrounding experimental apparatus is smaller than the dimension of the test mass itself. For the Advanced LIGO interferometric gravitational wave observatory, where the relevant test mass is a suspended 340 mm diameter cylindrical end mirror, the force noise power is increased by roughly a factor 40 by the presence of a similarly shaped reaction mass at a nominal separation of 5 mm. The force noise, of order 20 fN\rthz\ for $2 \times 10^{-6}$ Pa of residual H$_2$ gas, rivals quantum optical fluctuations as the dominant noise source between 10 and 30 Hz. We present here a numerical and analytical analysis for the gas damping force noise for Advanced LIGO, backed up by experimental evidence from several recent measurements. Finally, we discuss the impact of residual gas damping on the gravitational wave sensitivity and possible mitigation strategies.
108803577
Control Design of the Test Mass Release Mode for the LISA Pathfinder Mission
The LISA Technology Package (LTP) onboard the LISA Pathfinder mission features two high precision Gravitational Reference Sensors (GRS). Each GRS encompasses a free floating cubic Test Mass (TM) surrounded by a capacitive housing. The electrodes, hosted by the housing, form a set of variable capacitors with the TM and are used both for TM sensing and suspension. Moreover, each GRS contains a Caging Mechanism which sustains the TM during launch. Before the science phase of the mission begins, each TM is set free and the control system enters the TM Release Mode. This paper presents the design of the TM Release Mode: it covers equipment modelling, actuation strategy selection, disturbances estimation, controller law definition, performance results, and stability and robustness analysis.
118459662
Bayesian parameter estimation in the second LISA Pathfinder mock data challenge
A main scientific output of the LISA Pathfinder mission is to provide a noise model that can be extended to the future gravitational wave observatory, LISA. The success of the mission depends thus upon a deep understanding of the instrument, especially the ability to correctly determine the parameters of the underlying noise model. In this work we estimate the parameters of a simplified model of the LISA Technology Package instrument. We describe the LISA Technology Package by means of a closed-loop model that is used to generate the data, both injected signals and noise. Then, parameters are estimated using a Bayesian framework, and it is shown that this method reaches the optimal attainable error, the Cramer-Rao bound. We also address an important issue for the mission: how to efficiently combine the results of different experiments to obtain a unique set of parameters describing the instrument.