A learning approach to the detection of gravitational wave transients

We investigate the class of quadratic detectors (i.e., the statistic is a bilinear function of the data) for the detection of poorly modeled gravitational transients of short duration. We point out that all such detection methods are equivalent to passing the signal through a filter bank and linearly combine the output energy. Existing methods for the choice of the filter bank and of the weight parameters rely essentially on the two following ideas: (i) the use of the likelihood function based on a (possibly non-informative) statistical model of the signal and the noise, (ii) the use of Monte-Carlo simulations for the tuning of parametric filters to get the best detection probability keeping fixed the false alarm rate. We propose a third approach according to which the filter bank is "learned" from a set of training data. By-products of this viewpoint are that, contrarily to previous methods, (i) there is no requirement of an explicit description of the probability density function of the data when the signal is present and (ii) the filters we use are non-parametric. The learning procedure may be described as a two step process: first, estimate the mean and covariance of the signal with the training data; second, find the filters which maximize a contrast criterion referred to as deflection between the "noise only" and "signal+noise" hypothesis. The deflection is homogeneous to the signal-to-noise ratio and it uses the quantities estimated at the first step. We apply this original method to the problem of the detection of supernovae core collapses. We use the catalog of waveforms provided recently by Dimmelmeier et al. to train our algorithm. We expect such detector to have better performances on this particular problem provided that the reference signals are reliable.Comment: 22 pages, 4 figure

Optical response of a misaligned and suspended Fabry-Perot cavity

The response to a probe laser beam of a suspended, misaligned and detuned optical cavity is examined. A five degree of freedom model of the fluctuations of the longitudinal and transverse mirror coordinates is presented. Classical and quantum mechanical effects of radiation pressure are studied with the help of the optical stiffness coefficients and the signals provided by an FM sideband technique and a quadrant detector, for generic values of the product $\varpi \tau$ of the fluctuation frequency times the cavity round trip. A simplified version is presented for the case of small misalignments. Mechanical stability, mirror position entanglement and ponderomotive squeezing are accommodated in this model. Numerical plots refer to cavities under test at the so-called Pisa LF facility.Comment: 14 pages (4 figures) submitted to Phys. Rev.

Scaling, asymptotic scaling and Symanzik improvement. Deconfinement temperature in SU(2) pure gauge theory

We report on a high statistics simulation of SU(2) pure gauge field theory at finite temperature, using Symanzik action. We determine the critical coupling for the deconfinement phase transition on lattices up to 8 x 24, using Finite Size Scaling techniques. We find that the pattern of asymptotic scaling violation is essentially the same as the one observed with conventional, not improved action. On the other hand, the use of effective couplings defined in terms of plaquette expectation values shows a precocious scaling, with respect to an analogous analysis of data obtained by the use of Wilson action, which we interpret as an effect of improvement.Comment: 43 pages ( REVTeX 3.0, self-extracting shell archive, 13 PostScript figs.), report IFUP-TH 21/93 (2 TYPOS IN FORMULAS CORRECTED,1 CITATION UPDATED,CITATIONS IN TEXT ADDED

Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts

We outline the scientific motivation behind a search for gravitational waves associated with short gamma ray bursts detected by the InterPlanetary Network (IPN) during LIGO's fifth science run and Virgo's first science run. The IPN localisation of short gamma ray bursts is limited to extended error boxes of different shapes and sizes and a search on these error boxes poses a series of challenges for data analysis. We will discuss these challenges and outline the methods to optimise the search over these error boxes.Comment: Methods paper; Proceedings for Eduardo Amaldi 9 Conference on Gravitational Waves, July 2011, Cardiff, U

The status of Virgo

none143sìAfter almost 4 years of commissioning Virgo has started its first long science run. The recent commissioning and data analysis activities are summarized here.mixedF ACERNESE; M ALSHOURBAGY; P AMICO; F ANTONUCCI; S AOUDIA; P ASTONE; S AVINO; L BAGGIO; G BALLARDIN; F BARONE; L BARSOTTI; M BARSUGLIA; TH S BAUER; S BIGOTTA; S BIRINDELLI; M A BIZOUARD; C BOCCARA; F BONDU; L BOSI; S BRACCINI; C BRADASCHIA; A BRILLET; V BRISSON; D BUSKULIC; G CAGNOLI; E CALLONI; E CAMPAGNA; F CARBOGNANI; F CAVALIER; R CAVALIERI; G CELLA; E CESARINI; E CHASSANDE-MOTTIN; A-C CLAPSON; F CLEVA; E COCCIA; C CORDA; A CORSI; F COTTONE; J-P COULON; E CUOCO; S D'ANTONIO; A DARI; V DATTILO; M DAVIER; R DE ROSA; M DEL PRETE; L DI FIORE; A DI LIETO; M DI PAOLO EMILIO; A DI VIRGILIO; M EVANS; V FAFONE; I FERRANTE; F FIDECARO; I FIORI; R FLAMINIO; J-D FOURNIER; S FRASCA; F FRASCONI; L GAMMAITONI; F GARUFI; E GENIN; A GENNAI; A GIAZOTTO; L GIORDANO; V GRANATA; C GREVERIE; D GROSJEAN; G GUIDI; S HAMDANI; S HEBRI; H HEITMANN; P HELLO; D HUET; S KRECKELBERGH; P LA PENNA; M LAVAL; N LEROY; N LETENDRE; B LOPEZ; M LORENZINI; V LORIETTE; G LOSURDO; J-M MACKOWSKI; E MAJORANA; C N MAN; M MANTOVANI; F MARCHESONI; F MARION; J MARQUE; F MARTELLI; A MASSEROT; F MENZINGER; L MILANO; Y MINENKOV; C MOINS; J MOREAU; N MORGADO; S MOSCA; B MOURS; I NERI; F NOCERA; G PAGLIAROLI; C PALOMBA; F PAOLETTI; S PARDI; A PASQUALETTI; R PASSAQUIETI; D PASSUELLO; F PIERGIOVANNI; L PINARD; R POGGIANI; M PUNTURO; P PUPPO; P RAPAGNANI; T REGIMBAU; A REMILLIEUX; F RICCI; I RICCIARDI; A ROCCHI; L ROLLAND; R ROMANO; P RUGGI; G RUSSO; S SOLIMENO; A SPALLICCI; M TARALLO; R TERENZI; A TONCELLI; M TONELLI; E TOURNEFIER; F TRAVASSO; C TREMOLA; G VAJENTE; J F J VAN DEN BRAND; S VAN DER PUTTEN; D VERKINDT; F VETRANO; ANDREA VICERE; J-Y VINET; H VOCCA; M YVERTF., Acernese; M., Alshourbagy; P., Amico; F., Antonucci; S., Aoudia; P., Astone; S., Avino; L., Baggio; G., Ballardin; F., Barone; L., Barsotti; M., Barsuglia; TH S., Bauer; S., Bigotta; S., Birindelli; M. A., Bizouard; C., Boccara; F., Bondu; L., Bosi; S., Braccini; C., Bradaschia; A., Brillet; V., Brisson; D., Buskulic; G., Cagnoli; E., Calloni; E., Campagna; F., Carbognani; F., Cavalier; R., Cavalieri; G., Cella; Cesarini, Elisabetta; E., CHASSANDE MOTTIN; A. C., Clapson; F., Cleva; E., Coccia; C., Corda; A., Corsi; F., Cottone; J. P., Coulon; E., Cuoco; S., D'Antonio; A., Dari; V., Dattilo; M., Davier; R., DE ROSA; M., DEL PRETE; L., DI FIORE; A., DI LIETO; M., DI PAOLO EMILIO; A., DI VIRGILIO; M., Evans; V., Fafone; I., Ferrante; F., Fidecaro; I., Fiori; R., Flaminio; J. D., Fournier; S., Frasca; F., Frasconi; L., Gammaitoni; F., Garufi; E., Genin; A., Gennai; A., Giazotto; L., Giordano; V., Granata; C., Greverie; D., Grosjean; Guidi, GIANLUCA MARIA; S., Hamdani; S., Hebri; H., Heitmann; P., Hello; D., Huet; S., Kreckelbergh; P., LA PENNA; M., Laval; N., Leroy; N., Letendre; B., Lopez; M., Lorenzini; V., Loriette; G., Losurdo; J. M., Mackowski; E., Majorana; C. N., Man; M., Mantovani; F., Marchesoni; F., Marion; J., Marque; Martelli, Filippo; A., Masserot; F., Menzinger; L., Milano; Y., Minenkov; C., Moins; J., Moreau; N., Morgado; S., Mosca; B., Mours; I., Neri; F., Nocera; G., Pagliaroli; C., Palomba; F., Paoletti; S., Pardi; A., Pasqualetti; R., Passaquieti; D., Passuello; Piergiovanni, Francesco; L., Pinard; R., Poggiani; M., Punturo; P., Puppo; P., Rapagnani; T., Regimbau; A., Remillieux; F., Ricci; I., Ricciardi; A., Rocchi; L., Rolland; R., Romano; P., Ruggi; G., Russo; S., Solimeno; A., Spallicci; M., Tarallo; R., Terenzi; A., Toncelli; M., Tonelli; E., Tournefier; F., Travasso; C., Tremola; G., Vajente; J. F. J., VAN DEN BRAND; S., VAN DER PUTTEN; D., Verkindt; Vetrano, Flavio; Vicere', Andrea; J. Y., Vinet; H., Vocca; M., Yver

VIRGO: a large interferometer for gravitational wave detection started its first scientific run

International audienceThe VIRGO interferometer is the largest ground based European gravitational wave detector operating at the EGO Laboratory in the Pisa, Italy; countryside. During the last commissioning period relevant progress have been done in approaching its design sensitivity all over the detection bandwidth. Thanks to the effort of the whole Collaboration a long scientific run has been done collecting data for more than 4 months in conjunction with the LIGO detectors. The results obtained from the detector point of view are: a very good stability and a duty-cycle as high as 81% in science mode. In this paper we present the status of the VIRGO interferometer giving an overview of the experimental apparatus together with its most relevant features