123492651
Axion to magnon conversion. A scheme for the detection of galactic axions
Abstract We consider the possibility of detecting axions in the halo of our Galaxy by means of converting them into collective excitations of a ferromagnet. We calculate that, under optimal conditions, one can convert about 6000 axions per day in a 1 m 3 ferromagnet. The signal has an intrinsic diurnal modulation of order unit due to the combined effect of Earth rotation and motion of the solar system with respect to the galactic center. We discuss the ultimate limitations arising from thermal fluctuations of the magnetization.
118192054
Test‐Mass Release Phase Ground Testing for the LISA Pathfinder Mission
Aim of the LISA Test‐flight Package on board the LISA Pathfinder mission is to provide in‐flight demonstration of some of the LISA critical technologies in achieving the free‐fall condition of a LISA‐like test‐mass in the bandwidth from 1 to 30mHz. Accordingly, owing to high inertial loads arising during the launch phase the test‐mass needs to be firmly secured to the GRS, in order to avoid collision with the surrounding electrodes and housing parts. After the launch and orbit commissioning, the test‐mass must be released to floating conditions, in compliance with strict requirements of initial position and velocity, due to the low force and torque authority made available by the capacitive actuation system. The Caging Mechanism Assembly is being designed by Alcatel Alenia Space Italia and it constitutes the GRS subsystem dedicated to cage and release the test‐mass. The release phase to floating conditions has been identified as critical for the entire mission, therefore a ground‐based verification of suc...
120641812
Progress in the development of a position sensor for LISA drag-free control
We report on progress in the development of free-falling moving test-masses for LISA and for the related technology demonstration mission. We present simple formulae to evaluate the performance of the device as a function of the various design parameters, and we compare them with preliminary experimental results from a test prototype we are developing. Quantitative agreement is found. Finally, we present a control law, along with a performance simulation, for low-frequency electrostatic suspension of the test-mass with minimal perturbation of the motion within the measuring frequency band.
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
63844509
The LISA Pathfinder interferometry-hardware and system testing
Preparations for the LISA Pathfinder mission have reached an exciting stage. Tests of the engineering model (EM) of the optical metrology system have recently been completed at the Albert Einstein Institute, Hannover, and flight model tests are now underway. Significantly, they represent the first complete integration and testing of the space-qualified hardware and are the first tests on an optical system level. The results and test procedures of these campaigns will be utilized directly in the ground-based flight hardware tests, and subsequently during in-flight operations. In addition, they allow valuable testing of the data analysis methods using the MATLAB-based LTP data analysis toolbox. This paper presents an overview of the results from the EM test campaign that was successfully completed in December 2009.
120915791
Stochastic background detection with gravitational-wave resonant detectors
A linearized version of the standard Wiener filter theory is used to calculate the sensitivity to an isotropic stochastic gravitational-wave background of the AURIGA - NAUTILUS pair of ultra-low-temperature bar detectors, near to operating in coincidence in Italy, obtaining a sensitivity of . The addition of the VIRGO interferometric detector under construction in Italy improves the figure to . We also consider the pair formed by VIRGO and one large mass spherical detector located in a nearby available site in Italy and a pair of spherical detectors located at the AURIGA and NAUTILUS sites that promise to achieve sensitivities of .
120094772
Gravitational waves as deformations of embedded Einstein spaces
We show how approximate radiative solutions of Einstein's equations can be constructed using small deformations of Einstein spacetimes embedded into a pseudo-Euclidean flat space of higher dimension. Infinitesimal deformations are seen then as vector fields in EN. All geometrical quantities can be then expressed in terms of embedding functions zA and their deformations . Then we require the deformations to keep Einstein equations satisfied up to a given order in e. The system obtained is then analyzed in particular cases of the Minkowski and Schwarzschild manifolds taken as a starting point, and solutions of deformations of Einstein's equations displaying radiative behavior are found up to the third order of expansion in small parameter e.
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).
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.
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.
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