733 research outputs found
Gravitational Waves and GRBs from Tidal Disruption of Stars in the Center of Galaxies
Recent measurements of the Chandra satellite have shown that a supermassive
black hole of is located in the Galactic
Center; it seems probable that, from other observations, this fact is common in
the majority of galaxies. On the other hand, GRB explosions are typical
phenomenon linked to the galactic dynamics. In the present paper we discuss the
possibility that GRBs are tidal disruption of stars by supermassive black holes
located in the center of galaxies. This conjecture can be tested by a
gravitational wave detector of the class of AURIGA.Comment: 4 pages, 2 figures talk at Gamma Ray Burst Symposium - Santa Fe, New
Mexico (USA) September 8-12, 2003. There were added four new references and
the entrances of the two figures were written in a more clear wa
Antenna pattern of DUAL detectors of gravitational waves and its exploitation in a network of advanced interferometers
We investigate the directional sensitivity to plane gravitational waves (GWs) of DUAL detectors of cylindrical shape. Calculations make use of the finite element method to simulate the responses to the GW Riemann tensor of a single-mass DUAL (SMD) and of a tapered cylinder (TC) in their wide sensitivity bandwidth. We show that one SMD or a pair of TCs is able to cover both GW polarization amplitudes from almost all incoming directions. We discuss the achievable enhancement in tackling the inverse problem for high frequency [~(2–5) kHz] GWs by adding a TC detector to the future advanced LIGO–VIRGO network
Interferometric length metrology for the dimensional control of ultra-stable Ring Laser Gyroscopes
We present the experimental test of a method for controlling the absolute
length of the diagonals of square ring laser gyroscopes. The purpose is to
actively stabilize the ring cavity geometry and to enhance the rotation sensor
stability in order to reach the requirements for the detection of the
relativistic Lense-Thirring effect with a ground-based array of optical
gyroscopes. The test apparatus consists of two optical cavities 1.32 m in
length, reproducing the features of the ring cavity diagonal resonators of
large frame He-Ne ring laser gyroscopes. The proposed measurement technique is
based on the use of a single diode laser, injection locked to a frequency
stabilized He-Ne/Iodine frequency standard, and a single electro-optic
modulator. The laser is modulated with a combination of three frequencies
allowing to lock the two cavities to the same resonance frequency and, at the
same time, to determine the cavity Free Spectral Range (FSR). We obtain a
stable lock of the two cavities to the same optical frequency reference,
providing a length stabilization at the level of 1 part in , and the
determination of the two FSRs with a relative precision of 0.2 ppm. This is
equivalent to an error of 500 nm on the absolute length difference between the
two cavities
Methods for multi-detector burst gravitational wave search
In this paper, a review of methods of data exchange and multi-detector analysis is given. Details of data exchange parameters will also be discussed. We focus on the coherent network search which turns out to be a fundamental step towards the overcoming of ambiguity in parameter estimation of a gravitational wave in the low signal-to-noise ratio regime
Electromagnetic waves in gravitational wave spacetimes
We have considered the propagation of electromagnetic waves in a space-time representing an exact gravitational plane wave and calculated the induced changes on the four-potential field Aμ of a plane electromagnetic wave. By choosing a suitable photon round-trip in a Michelson interferometer, we have been able to identify the physical effects of the exact gravitational wave on the electromagnetic field, i.e. phase shift, change of the polarization vector, angular deflection and delay. These results have been exploited to study the response of an interferometric gravitational wave detector beyond the linear approximation of the general theory of relativity. A much more detailled examination of this problem can be found in our paper recently published in Classical and Quantum Gravity (28 (2011) 235007)
Laser induced fluorescence for axion dark matter detection: a feasibility study in YLiF:Er
We present a detection scheme to search for QCD axion dark matter, that is
based on a direct interaction between axions and electrons explicitly predicted
by DFSZ axion models. The local axion dark matter field shall drive transitions
between Zeeman-split atomic levels separated by the axion rest mass energy . Axion-related excitations are then detected with an upconversion scheme
involving a pump laser that converts the absorbed axion energy (
hundreds of eV) to visible or infrared photons, where single photon
detection is an established technique. The proposed scheme involves rare-earth
ions doped into solid-state crystalline materials, and the optical transitions
take place between energy levels of electron configuration. Beyond
discussing theoretical aspects and requirements to achieve a cosmologically
relevant sensitivity, especially in terms of spectroscopic material properties,
we experimentally investigate backgrounds due to the pump laser at temperatures
in the range K. Our results rule out excitation of the upper Zeeman
component of the ground state by laser-related heating effects, and are of some
help in optimizing activated material parameters to suppress the
multiphonon-assisted Stokes fluorescence.Comment: 8 pages, 5 figure
- …