Università degli Studi di Napoli "Federico II"
Dipartment of Physics
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
He-Ne ring lasers are, actually, the most sensitive devices for inertial rotation measurements. Depending on their linear dimensions, they find applications in different fields: from inertial navigation to structural engineering, from... more
He-Ne ring lasers are, actually, the most sensitive devices for inertial rotation measurements. Depending on their linear dimensions, they find applications in different fields: from inertial navigation to structural engineering, from metrology to geophysics and fundamental physics [1,2]. Here we report the recent progresses toward the development of GINGER-Gyroscopes IN GEneral Relativity [3 j, a triaxial ultra-sensitive ring laser gyroscope whose primary target is a ground measurement the Lense-Thirring effect, a small shift of the Earth rotation rate foreseen by Einstein's General Relativity. This target implies a measurement of the Earth rotation rate with a sensitivity better than one part over J alii and so requires a high level of stability and accuracy of the laser array and of the gyroscope stability. The main part of the research activity presented in this paper involves, then, a strict control of the systematic errors related to the fluctuation of the optical cavity geometry and of the laser parameters.
- by Jacopo Belfi and +3
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GINGER is a proposed tridimensional array of laser gyroscopes with the aim of measuring the Lense-Thirring effect, predicted by the General Relativity theory, in a terrestrial laboratory environment. We discuss the required accuracy, the... more
GINGER is a proposed tridimensional array of laser gyroscopes with the aim of measuring the Lense-Thirring effect, predicted by the General Relativity theory, in a terrestrial laboratory environment. We discuss the required accuracy, the methods to achieve it, and the preliminary experimental work in this direction.
- by Jacopo Belfi and +3
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- Mathematical Physics, Physics, Theoretical Physics, Optics
Ultra sensitive ring laser gyroscopes are regarded as potential detectors of the general relativistic frame-dragging effect due to the rotation of the Earth: the project name is GINGER (Gyroscopes IN GEneral Relativity), a ground-based... more
Ultra sensitive ring laser gyroscopes are regarded as potential detectors of the general relativistic frame-dragging effect due to the rotation of the Earth: the project name is GINGER (Gyroscopes IN GEneral Relativity), a ground-based triaxial array of ring lasers aiming at measuring the Earth rotation rate with an accuracy of 10 −14 rad/s. Such ambitious goal is now within reach as large area ring lasers are very close to the necessary sensitivity and stability. However, demanding constraints on the geometrical stability of the laser optical path inside the ring cavity are required. Thus we have started a detailed study of the geometry of an optical cavity, in order to find a control strategy for its geometry which could meet the specifications of the GINGER project. As the cavity perimeter has a stationary point for the square configuration, we identify a set of transformations on the mirror positions which allows us to adjust the laser beam steering to the shape of a square. We show that the geometrical stability of a square cavity strongly increases by implementing a suitable system to measure the mirror distances, and that the geometry stabilization can be achieved by measuring the absolute lengths of the two diagonals and the perimeter of the ring.
Abstract. The Virgo gravitational wave detector is an interferometer with 3 km long arms in construction near Pisa to be commissioned in the year 2000. Virgo has been designed to achieve a strain sensitivity (SNR= 1) of a few times 10− 23... more
Abstract. The Virgo gravitational wave detector is an interferometer with 3 km long arms in construction near Pisa to be commissioned in the year 2000. Virgo has been designed to achieve a strain sensitivity (SNR= 1) of a few times 10− 23 Hz− 1/2 at 200 Hz. A large effort has gone into the conception of the mirror suspension system, which is expected to reduce noise to the level of 10− 21 Hz− 1/2 at 10 Hz. The expected signals and main sources of noise are briefly discussed; the choices made are illustrated together with the present ...
The simulation program developped for the VIRGO collaboration is designed as a general purpose tool for detector design, detector commissioning and data analysis. It allows to simulate in an integrated way some expected gravitational wave... more
The simulation program developped for the VIRGO collaboration is designed as a general purpose tool for detector design, detector commissioning and data analysis. It allows to simulate in an integrated way some expected gravitational wave signals as well as many aspects of the detector response. The general structure and contents of the simulation program are described, as well as a typical application example.
- by S. Solimeno and +5
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- Gravitational Wave Detection
Virgo is an experiment aiming at the detection of gravitational waves emitted by astrophysical sources. Its detector, based on a 3km arms interferometer, is a complex setup which requires several digital control loops running up to 10kHz,... more
Virgo is an experiment aiming at the detection of gravitational waves emitted by astrophysical sources. Its detector, based on a 3km arms interferometer, is a complex setup which requires several digital control loops running up to 10kHz, an accurate and reliable central timing system and an efficient data acquisition, all of them being distributed over 3km. We overview here the main hardware and software components developed for the data acquisition system (DAQ) and its current architecture. Then, we briefly discuss its connections with interferometer's controls, especially through the automation of the interferometer's startup procedure. Then, we describe the tools used to monitor the DAQ and the performances we measured with them. Finally, are described also the tools developped for the online detector monitoring, mandatory complement of the DAQ for the commissioning of the Virgo detector.
The classical limit of quantum q-oscillators suggests an interpretation of the deformation as a way to introduce non linearity. Guided by this idea, we considered q-fields, the partition fumction, and compute a consequence on specific... more
The classical limit of quantum q-oscillators suggests an interpretation of the deformation as a way to introduce non linearity. Guided by this idea, we considered q-fields, the partition fumction, and compute a consequence on specific heat and second order correlation function of the q-oscillator which may serve for experimental checks for the non linearity.
- by S. Solimeno and +1
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- Oscillations, Second Order, Classical Limit, Partition Function
A unitary transformation of the N -ion Jaynes-Cummings Hamiltonian is proposed. It is shown that any approximate expression of the evolution operator associated with the transformed Hamiltonian retains its validity independently from the... more
A unitary transformation of the N -ion Jaynes-Cummings Hamiltonian is proposed. It is shown that any approximate expression of the evolution operator associated with the transformed Hamiltonian retains its validity independently from the intensity of the external driving field. In particular, using the rotating wave approximation, one obtains a solution for the N -ion Jaynes-Cummings model which improves the standard rotating wave approximation solution.
and their productD =P 11P22 −P 12P21 . An analogous system holds for δς Y SN J withχ J replaced byχ Y J . The output field contains a component (Eqs. ) δã OUT ∝ e i̟τZ 1 δς 1 + e i̟τ /2Z 2 δς 2 ·v 1 proportional to δς 1,2 through the... more
and their productD =P 11P22 −P 12P21 . An analogous system holds for δς Y SN J withχ J replaced byχ Y J . The output field contains a component (Eqs. ) δã OUT ∝ e i̟τZ 1 δς 1 + e i̟τ /2Z 2 δς 2 ·v 1 proportional to δς 1,2 through the matricesZ J = G · Φ · ς J ·G and a shot noiseĜ OUT ·δâ SN 1 + t2 t1Ĝ ·δâ SN
A theoretical investigation has been made on the Dust ion-acoustic (DIA) Gardner solitons (GSs) and double layers (DLs) in electronegative plasma consisting of inertial positive and negative ions, super-thermal (kappa distributed)... more
A theoretical investigation has been made on the Dust ion-acoustic (DIA) Gardner solitons (GSs) and double layers (DLs) in electronegative plasma consisting of inertial positive and negative ions, super-thermal (kappa distributed) electrons, and negatively charged static dust. The standard reductive perturbation method is employed to derive the Korteweg-de Vries (K-dV), modified K-dV (mK-dV), and standard Gardner equations, which admits solitary waves (SWs) and DLs solutions. It have been found that GSs and DLs exist for α around its critical value α c , where α c is the value of α corresponding to the vanishing of the nonlinear coefficient of the K-dV equation. The parametric regimes for the existence of both the positive as well as negative SWs and negative DLs are obtained. The basic features of DIA SWs and DLs are analyzed and it has been found that the polarity, speed, height, thickness of such DIA SWs and DLs structures, are significantly modified due to the presence of two types of ions and spectral index (κ) of super-thermal electrons. It has also been found that the characteristics of DIA GSs and DLs, are different from that of the K-dV solitons and mK-dV solitons. The relevance of our results to different interstellar space plasma situations are discussed.
- by Tahmina Akhter
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Поступила в редакцию 21.05.2012 г. Окончательный вариант получен 27.09.2012 г.
- by Tahmina Akhter
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We study the linearized equations describing the propagation of gravitational waves through dust. In the leading order of the WKB approximation, dust behaves as a nondispersive, nondissipative medium. Taking advantage of these features,... more
We study the linearized equations describing the propagation of gravitational waves through dust. In the leading order of the WKB approximation, dust behaves as a nondispersive, nondissipative medium. Taking advantage of these features, we explore the possibility that a gravitational wave from a distant source gets trapped by the gravitational field of a long filament of galaxies of the kind seen in the large scale structure of the Universe. Such a waveguiding effect may lead to a huge magnification of the radiation flux from distant sources, thus lowering the sensitivity threshold required for a successful detection of gravitational waves by detectors such as VIRGO, LIGO, and LISA. ͓S0556-2821͑98͒01220-X͔
- by Salvatore Capozziello and +2
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- Quantum Physics
A detailed investigation is presented of the energy-momentum tensor approach to the evaluation of the force acting on a rigid Casimir cavity in a weak gravitational field. Such a force turns out to have opposite direction with respect to... more
A detailed investigation is presented of the energy-momentum tensor approach to the evaluation of the force acting on a rigid Casimir cavity in a weak gravitational field. Such a force turns out to have opposite direction with respect to the gravitational acceleration. The order of magnitude for a multi-layer cavity configuration is derived and experimental feasibility is discussed, taking into account current technological resources.
- by Giampiero Esposito and +1
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- High Energy Physics
We review and assess a part of the recent work on Casimir apparatuses in the weak gravitational field of the Earth. For a free, real massless scalar field subject to Dirichlet or Neumann boundary conditions on the parallel plates, the... more
We review and assess a part of the recent work on Casimir apparatuses in the weak gravitational field of the Earth. For a free, real massless scalar field subject to Dirichlet or Neumann boundary conditions on the parallel plates, the resulting regularized and renormalized energy-momentum tensor is covariantly conserved, while the trace anomaly vanishes if the massless field is conformally coupled to gravity. Conformal coupling also ensures a finite Casimir energy and finite values of the pressure upon parallel plates. These results have been extended to an electromagnetic field subject to perfect conductor (hence idealized) boundary conditions on parallel plates, by various authors.