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We show that from the R^{2} high order gravity theory it is possible to produce, in the linearized approch, particles which can be seen like massive modes of gravitational waves (GWs). The presence of the mass generates a longitudinal force in addition of the transverse one which is proper of the massless gravitational waves and the response an interferometer to the effect is computed. This could be, in principle, important to discriminate among the gravity theories. The presence of the mass could also have important applications in cosmology because the fact that gravitational waves can have mass could give a contribution to the dark matter of the Universe., Comment: Accepted for the International Journal of Modern Physics A

This paper is a review of a previous research on gravitational waves from the R^-1 high order theory of gravity. It is shown that a massive scalar mode of gravitational waves from the R^-1 theory generates a longitudinal force in addition of the transverse one which is proper of the massless gravitational waves and the response of an arm of an interferometer to this longitudinal effect in the frame of a local observer is computed. Important conseguences from a theoretical point of view could arise from this approach, because it opens to the possibility of using the signals seen from interferometers to understand which is the correct theory of gravitation., Comment: To appear in Proc. of the 10th ICATPP International Conference on Advanced Technology and Particle Physics (Villa Olmo Como, 8-12 october 2007)

In this this paper the stochastic background of gravitational waves (SBGWs) is analyzed with the auxilium of the WMAP data. We emphasize that, in general, in previous works in the literature about the SBGWs, old COBE data were used. After this, we want to face the problem of how the SBGWs and f(R) gravity can be related, showing, vice versa, that a revealed SBGWs could be a powerly probe for a given theory of gravity. In this way, it will also be shown that the conformal treatment of SBGWs can be used to parametrize in a natural way f(R) theories., Comment: To appear in "Proceedings of the Fourth Italian-Sino Workshop on Relativistic Astrophysics" July 20-30 2007, Pescara, Italy

The investigation of the transverse effect of gravitational waves (GWs) could constitute a further tool to discriminate among several relativistic theories of gravity on the ground. After a review of the TT gauge, the transverse effect of GWs arising by standard general relativity (called Einstein's GWs in this paper) is reanalized with a different choice of coordinates. In the chosen gauge test masses have an apparent motion in the direction of propagation of the wave, while in the transverse direction they appear at rest. Of course, this is only a gauge artefact. In fact, from careful investigation of this particular gauge, it is shown that the tidal forces associated with GWs act along the directions orthogonal to the direction of propagation of waves. In the analysis it is also shown, in a heuristic way, that the transverse effect of Einstein's GWs arises from the propagation of the waves at the speed of the light, thus only massless GWs are purely transverse. But, because the physics of gravitational waves has to be investigated by studing the tidal forces as appearing in the geodesic deviation equation and directly in a laboratory environment on Earth, an analysis of these tidal forces and of the transverse effect in the frame of the local observer is also performed. After this, for a further better understanding of the transverse effect, an example of a wave, which arises from scalar tensor gravity, with both transverse and genuinely longitudinal modes is given and discussed. In the example the connection between the longitudinal component and the velocity of the wave will be mathematical shown. At the end of this paper the review of the TT gauge is completed, recovering the gauge invariance between the presented gauge and the TT one., Comment: Review paper, accepted for the International Journal of Modern Physics A

A stochastic background of relic gravitational waves is achieved by the so called adiabatically-amplified zero-point fluctuations process derived from early inflation. In principle, it provides a distinctive spectrum of relic gravitational waves. In the framework of scalar-tensor gravity, we discuss the scalar modes of gravitational waves and the primordial production of this scalar component which is generated beside tensorial one. We discuss also the upper limit for such a relic scalar component with respect to the WMAP constraints., Comment: 7 pages, 1 figure

After a review of the frequency - dependent angular pattern of interferometers in the TT gauge for scalar gravitational waves (SGWs), which has been recently analysed by Capozziello and Corda, in this letter the result is used to study the cross correlation between the Virgo interferometer and the MiniGRAIL resonant sphere. It is shown that the overlap reduction function for the cross correlation bewteen Virgo and the monopole mode of MiniGRAIL is very small, but a maximum is also found in the correlation at about 2710Hz, in the range of the MiniGRAIL sensitivity, Comment: Accepted for Modern Physics Letters A

Recently some papers in the literature have shown the presence and importance of the so-called {}"magnetic" components of gravitational waves (GWs), which have to be taken into account in the context of the total response functions of interferometers for GWs propagating from arbitrary directions. In this paper the response functions for the magnetic components are re-analysed in the full frequency dependence answering to the question of the title., Comment: To appear in proceedings of the Rencontres de Moriond, Gravitational Waves and Experimental Gravity, La Thuile, Val d'Aosta, Italy (March 11-18, 2007)

A Lagrangian formulation describing the electromagnetic interaction - mediated by topologically massive vector bosons - between charged, spin-(1/2) fermions with an abelian magnetic monopole in a curved spacetime with non-minimal coupling and torsion potential is presented. The covariant field equations are obtained. The issue of coexistence of massive photons and magnetic monopoles is addressed in the present framework. It is found that despite the topological nature of photon mass generation in curved spacetime with isotropic dilaton field, the classical field theory describing the nonrelativistic electromagnetic interaction between a point-like electric charge and magnetic monopole is inconsistent., Comment: 18 pages, no figures

The aim of this paper is to show the gauge-invariance on the response of interferometers to gravitational waves (GWs). In this process, after a review of results on the Tranverse-Traceless (TT) gauge, where, in general, the theoretical computations on GWs are performed, which is due for completness, we analyse the gauge of the local observer, which represents the gauge of a laboratory environment on Earth. The gauge-invariance between the two gauges is shown in its full angular and frequency dependences. In previous works in the literature this gauge-invariance was shown only in the low frequencies approximation or in the simplest geometry of the interferometer in respect to the propagating GW (i.e. both of the arms of the interferometer are perpendicular to the propagating GW). As far as the computation of the response functions in the gauge of the local observer is concerned, a common misconception about interferometers is also clarifed., Comment: This paper has been withdrawn by the author because an improved and updated version has been put in the archive

The strict analogy between scalar-tensor theories of gravity and high order gravity is well known in literature. In this paper it is shown that, from a particular high order gravity theory known in literature, it is possible to produce, in the linearized approch, particles which can be seen like massive scalar modes of gravitational waves and the response of interferometers to this type of particles is analyzed. The presence of the mass generates a longitudinal force in addition of the transverse one which is proper of the massless gravitational waves and the response of an arm of an interferometer to this longitudinal effect in the frame of a local observer is computed. This longitudinal response function is directly connected with the function of the Ricci scalar in the particular action of this high order theory. Important conseguences from a theoretical point of view could arise from this approach, because it opens to the possibility of using the signals seen from interferometers to understand which is the correct theory of gravitation., Comment: Accepted for Journal of Cosmology and Astroparticle Physics

With an enlighting analysis, Baskaran and Grishchuk have recently shown the presence and importance of the so-called ``magnetic'' components of gravitational waves (GWs), which have to be taken into account in the context of the total response functions of interferometers for GWs propagating from arbitrary directions. In this paper more detailed angular and frequency dependences of the response functions for the magnetic components are given in the approximation of wavelength much larger than the linear dimensions of the interferometer, with a specific application to the parameters of the LIGO and Virgo interferometers. Our results agree with the work of Baskaran and Grishchuk in which it has been shown that the identification of ``electric'' and ``magnetic'' contributions is unambiguous in the long-wavelength approximation. At the end of this paper the angular and frequency dependences of the total response functions of the LIGO and Virgo interferometers are given. In the high-frequency regime the division on ``electric'' and ``magnetic'' components becomes ambiguous, thus the full theory of gravitational waves has to be used. Our results are consistent with the ones of Baskaran and Grishchuk in this case too., Comment: Accepted for the International Journal of Modern Physics D

Starting from a continuum theory of defects, that is the analogous to three-dimensional Einstein-Cartan-Sciama-Kibble gravity, we consider a charged particle with spin 1/2 propagating in a uniform magnetic field coincident with a wedge dispiration of finite extent. We assume the particle is bound in the vicinity of the dispiration by long range attractive (harmonic) and short range (inverse square) repulsive potentials. Moreover, we consider the effects of spin-torsion and spin-magnetic field interactions. Exact expressions for the energy eigenfunctions and eigenvalues are determined. The limit, in which the defect region becomes singular, is considered and comparison with the electromagnetic Aharonov-Bohm effect is made., Comment: 10 pages

It is well known that one cannot construct a self-consistent quantum field theory describing the non-relativistic electromagnetic interaction mediated by massive photons between a point-like electric charge and a magnetic monopole. We show that, indeed, this inconsistency arises in the classical theory itself. No semi-classic approximation or limiting procedure for the Dirac constant approaching to zero is used. As a result, the string attached to the monopole emerges as visible also if finite-range electromagnetic interactions are considered in classical framework., Comment: 10 pages, no figures

In the earlier work arXiv:0706.3782 we studied the cross correlation between the Virgo interferometer and the MiniGRAIL resonant sphere for the detection of relic scalar gravitational waves (SGWs). We have shown that the overlap reduction function for the cross correlation between Virgo and the monopole mode of MiniGRAIL is very small, but a maximum was also found in the correlation at about 2710Hz, in the range of the MiniGRAIL sensitivity. In this paper the analysis is improved. After carefully reviewing the response function of interferometers to SGWs directly in the gauge of the local observer, the result is used to analyze the cross correlation between the two LIGO interferometers in their advanced configuration for a potential detection of relic SGWs and to release a lower bound for the integration time of such a detection. By using a new, frequency-dependent, overlap reduction function, a comparison with previous low-frequency approximations is therefore discussed. This is the first time that such a cross-correlation is computed in all the frequency spectrum of relic SGWs. The computation of a better signal to noise ratio is very important to understand if a scalar component of GWs is present at high frequency. With the new overlap reduction function, an order of magnitude is gained concerning the integration time for detecting the relic SGWs' signal. This could be very important for a potential detection if advanced projects further improve their sensitivity. ., Comment: 18 pages, 3 figures. Definitive version accepted for publication in New Astronomy. Sequel of arXiv:0706.3782

A derivation of the optical axis lenght fluctations due by tilts of the mirrors of the Fabry-Perot cavity of long-baseline interferometers for the detection of gravitational waves in presence of the gravitational field of the earth is discussed. By comparing with the typical tilt-induced noises it is shown that this potential signal, which is considered a weak source of noise, is negligible for the first generation of gravitational waves interferometers, but, in principle, this effect could be used for high precision measures of the gravitational acceleration if advanced projects will achieve an high sensitivity. In that case the precision of the misure could be higher than the gravimeter realized by the Istituto di Metrologia ``Gustavo Colonnetti''., Comment: Submitted to General Relativity and Gravitation

Following some ideas in the Landau book, some corrections about errors in the old literature on scalar gravitational waves are given and discussed. Even if such errors can be considered not important from the point of view of observations, because they do not alter the interferometric response function for scalar gravitational waves, the presented analysis is due and very important for a sake of completeness and for a better understanding of the linearized theory of Scalar-Tensor Gravity, Comment: This paper has been withdrawn by the author due to errors in the computations

Recently, with an enlighting treatment, Baskaran and Grishchuk have shown the presence and importance of the so-called ``magnetic'' components of gravitational waves (GWs), which have to be taken into account in the context of the total response functions of interferometers for GWs propagating from arbitrary directions. In this paper the analysis of the response functions for the magnetic components is generalized in its full frequency dependence, while in the work of Baskaran and Grishchuk the response functions were computed only in the approximation of wavelength much larger than the linear dimensions of the interferometer. It is also shown that the response functions to the magnetic components grow at high frequencies, differently from the values of the response functions to the well known ordinary components that decrease at high frequencies. Thus the magnetic components could in principle become the dominant part of the signal at high frequencies. This is important for a potential detection of the signal at high frequencies and confirms that the magnetic contributions must be taken into account in the data analysis. More, the fact that the response functions of the magnetic components grow at high frequencies shows that, in principle, the frequency-range of Earth-based interferometers could extend to frequencies over 10000 Hz., Comment: Accepted for the International Journal of Modern Physics A