arXiv subjects

Lorenzo Iorio

Publications and source records attributed to Lorenzo Iorio.

At least 235 records · Page 13Linked to original sources

arXiv2006

Doppler Effects from Bending of Light Rays in Curved Space-Times

We study Doppler effects in curved space-time, i.e. the frequency shifts induced on electromagnetic signals propagating in the gravitational field. In particular, we focus on the frequency shift due to the bending of light rays in weak gravitational fields. We consider, using the PPN formalism, the gravitational field of an axially symmetric distribution of mass. The zeroth order, i.e. the sphere, is studied then passing to the contribution of the quadrupole moment, and finally to the case of a rotating source. We give numerical estimates for situations of physical interest, and by a very preliminary analysis, we argue that analyzing the Doppler effect could lead, in principle, in the foreseeable future, to the measurement of the quadrupole moment of the giant planets of the Solar System.

gr-qc↗

arXiv2006

On the impossibility of measuring the general relativistic part of the terrestrial acceleration of gravity with superconducting gravimeters

In this paper we very preliminarily investigate the possibility of measuring the post-Newtonian general relativistic gravitoelectric and gravitomagnetic components of the acceleration of gravity on the Earth, in continuous regime, with two absolute measurements at the equator and the south pole with superconducting gravimeters. The magnitudes of such relativistic effects are 10^-10 m s^-2 and 10^-11 m s^-2, respectively. Unfortunately, the present-day uncertainties in the Earth's geodetic parameters which enter the classical Newtonian terms induce systematic errors 1-2 orders of magnitude larger than the relativistic ones. Moreover, a \sim 1 ngal sensitivity can be reached by the currently available superconducting gravimeters, but only for relative measurements.

gr-qc↗

arXiv2006

What do the orbital motions of the outer planets of the Solar System tell us about the Pioneer anomaly?

In this paper we investigate the effects that an anomalous acceleration as that experienced by the Pioneer spacecraft after they passed the 20 AU threshold would induce on the orbital motions of the Solar System planets placed at heliocentric distances of 20 AU or larger as Uranus, Neptune and Pluto. It turns out that such an acceleration, with a magnitude of 8.74\times 10^-10 m s^-2, would affect their orbits with secular and short-period signals large enough to be detected according to the latest published results by E.V. Pitjeva, even by considering errors up to 30 times larger than those released. The absence of such anomalous signatures in the latest data rules out the possibility that in the region 20-40 AU of the Solar System an anomalous force field inducing a constant and radial acceleration with those characteristics affects the motion of the major planets.

gr-qc↗

arXiv2006

Solar System planetary orbital motions and dark matter

In this paper we explicitly work out the effects that a spherically symmetric distribution of dark matter with constant density would induce on the Keplerian orbital elements of the Solar System planets and compare them with the latest results in planetary orbit determination from the EPM2004 ephemerides. It turns out that the longitudes of perihelia and the mean longitudes are affected by secular precessions. The resulting upper bounds on dark matter density, obtained from the EPM2004 formal errors in the determined mean longitude shifts over 90 years, lie in the range 10^-19-10^-20 g cm^-3 with a peak of 10^-22 g cm^-3 for Mars. Suitable combinations of the planetary mean longitudes and perihelia, which cancel out the aliasing impact of some of the unmodelled or mismodelled forces of the dynamical models of EPM2004, yield a global upper bound of 7 10^-20 g cm^-3 and 4 10^-19 g cm^-3, respectively.

gr-qc↗

arXiv2006

On the mean anomaly and the Lense-Thirring effect

In this brief note we reply to the authors of a recent preprint in which an alleged explicit proposal of using the mean anomaly of the LAGEOS satellites to measure the general relativistic Lense-Thirring effect in the gravitational field of the Earth is attributed to the present author.

gr-qc↗

arXiv2005

Are we far from testing general relativity with the transiting extrasolar planet HD 209458b `Osiris'?

In this paper we investigate the possibility of measuring the general relativistic gravitoelectric contribution P^(GE) to the orbital period P of the transiting exoplanet HD 209458b 'Osiris'. It turns out that the predicted magnitude of such an effect is \sim 0.1 s, while the most recent determinations of the orbital period of HD 209458b with the photometric transit method are accurate to \sim 0.01 s. The present analysis shows that the major limiting factor is the \sim 1 m s^-1 sensitivity in the measurement of the projected semiamplitude of the star's radial velocity K. Indeed, it affects the determination of the mass m of the planet which, in turn, induces a systematic error in the Keplerian period P^(0) of \sim 8 s. It is of crucial importance because P^(0) should be subtracted from the measured period in order to extract the relativistic correction. The present-day uncertainty in $m$ does not yet make necessary the inclusion of relativistic corrections in the data-reduction process of the determination of the system's parameters. The present situation could change only if improvements of one-two orders of magnitude in the ground-based Doppler spectroscopy technique occurred.

gr-qc↗

arXiv2005

How the orbital period of a test particle is modified by the Dvali-Gabadadze-Porrati gravity?

In addition to the pericentre ω, the mean anomaly M and, thus, the mean longitude λ, also the orbital period Pb and the mean motion $n$ of a test particle are modified by the Dvali-Gabadadze-Porrati gravity. While the correction to Pb depends on the mass of the central body and on the geometrical features of the orbital motion around it, the correction to $n$ is independent of them, up to terms of second order in the eccentricity $e$. The latter one amounts to about 2\times 10^-3 arcseconds per century. The present-day accuracy in determining the mean motions of the inner planets of the Solar System from radar ranging and differential Very Long Baseline Interferometry is 10^-2-5\times 10^-3 arcseconds per century, but it should be improved in the near future when the data from the spacecraft to Mercury and Venus will be available.

gr-qc↗

arXiv2005

Can Solar System observations tell us something about the cosmological constant?

In this note we show that the latest determinations of the residual Mercury's perihelion advance, obtained by accounting for almost all known Newtonian and post-Newtonian orbital effects, yields only very broad constraints on the cosmological constant. Indeed, from δ\dotω=-0.0036 + - 0.0050 arcseconds per century one gets -2 10^-34 km^-2 < Lambda < 4 10^-35 km^-2. The currently accepted value for Lambda, obtained from many independent cosmological and large-scale measurements, amounts to almost 10^-46 km^-2.

gr-qc↗

arXiv2005

Spin precession in the Dvali-Gabadadze-Porrati braneworld scenario

In this letter we work out the secular precession of the spin of a gyroscope in geodesic motion around a central mass in the framework of the Dvali-Gabadadze-Porrati multidimensional gravity model. Such an effect, which depends on the mass of the central body and on the orbit radius of the gyroscope, contrary to the precessions of the orbital elements of the orbit of a test body, is far too small to be detected.

gr-qc↗

arXiv2005

The impact of the new Earth gravity model EIGEN-CG03C on the measurement of the Lense-Thirring effect with some existing Earth satellites

The impact of the latest combined CHAMP/GRACE/terrestrial measurements Earth gravity model EIGEN-CG03C on the measurement of the Lense-Thirring effect with some linear combinations of the nodes of some of the existing Earth's artificial satellites is presented. The 1-sigma upper bound of the systematic error in the node-node LAGEOS-LAGEOS II combination is 3.9% (4% with EIGEN-GRACE02S, \sim 6% with EIGEN-CG01C and \sim 9% with GGM02S), while it is 1$% for the node-only LAGEOS-LAGEOS II-Ajisai-Jason-1 combination (2% with EIGEN-GRACE02S, 1.6% with EIGEN-CG01C and 2.7% with GGM02S).

gr-qc↗

arXiv2005

The Lense-Thirring effect in the Jovian system of the Galilean satellites and its measurability

In this paper we investigate the possibility of measuring the post-Newtonian general relativistic gravitomagnetic Lense-Thirring effect in the Jovian system of its Galilean satellites Io, Europa, Ganymede and Callisto in view of recent developments in processing and modelling their optical observations spanning a large time interval (125 years). The present day best observations have an accuracy between several kilometers to few tens of kilometers, which is just the order of magnitude of the Lense-Thirring shifts of the orbits of the Galilean satellites over almost a century. From a comparison between analytical development and numerical integration it turns out that, unfortunately, most of the secular component of the gravitomagnetic signature is removed in the process of fitting the initial conditions. Indeed, an estimation of the magnitude of the Lense-Thirring effect in the ephemerides residuals is given; the resulting residuals have a maximum magnitude of 20 meters only (over 125 years).

gr-qc↗

arXiv2005

Secular increase of the Astronomical Unit and perihelion precessions as tests of the Dvali-Gabadadze-Porrati multi-dimensional braneworld scenario

An unexpected secular increase of the Astronomical Unit, the length scale of the Solar System, has recently been reported by three different research groups (Krasinsky and Brumberg, Pitjeva, Standish). The latest JPL measurements amount to 7+-2 m cy^-1. At present, there are no explanations able to accommodate such an observed phenomenon, neither in the realm of classical physics nor in the usual four-dimensional framework of the Einsteinian General Relativity. The Dvali-Gabadadze-Porrati braneworld scenario, which is a multi-dimensional model of gravity aimed to the explanation of the observed cosmic acceleration without dark energy, predicts, among other things, a perihelion secular shift, due to Lue and Starkman, of 5 10^-4 arcsec cy^-1 for all the planets of the Solar System. It yields a variation of about 6 m cy^-1 for the Earth-Sun distance which is compatible at 1-sigma level with the observed rate of the Astronomical Unit. The recently measured corrections to the secular motions of the perihelia of the inner planets of the Solar System are in agreement, at 1-sigma level, with the predicted value of the Lue-Starkman effect for Mercury and Mars and at 2-sigma level for the Earth.

gr-qc↗

arXiv2005

On the effects of the Dvali-Gabadadze-Porrati braneworld gravity on the orbital motion of a test particle

In this paper we explicitly work out the secular perturbations induced on all the Keplerian orbital elements of a test body to order O(e^2) in the eccentricity e by the weak-field long-range modifications of the usual Newton-Einstein gravity due to the Dvali-Gabadadze-Porrati (DGP) braneworld model. The Gauss perturbative scheme is used. It turns out that the argument of pericentre and the mean anomaly are affected by secular rates which are independent of the semimajor axis of the orbit of the test particle. The first nonvaishing eccentricity-dependent corrections are of order O(e^2). For circular orbits the Lue-Starkman (LS) effect on the pericentre is obtained. Some observational consequences are discussed for the Solar System planetary mean longitudes lambda which would undergo a 1.2\cdot 10^-3 arcseconds per century braneworld secular precession. According to recent data analysis over 92 years for the EPM2004 ephemerides, the 1-sigma formal accuracy in determining the Martian mean longitude amounts to 3\cdot 10^-3 milliarcseconds, while the braneworld effect over the same time span would be 1.159 milliarcseconds. The major limiting factor is the 2.6\cdot 10^-3 arcseconds per century systematic error due to the mismodelling in the Keplerian mean motion of Mars. A suitable linear combination of the mean longitudes of Mars and Venus may overcome this problem. The formal, 1-sigma obtainable observational accuracy would be \sim 7%. The systematic error due to the present-day uncertainties in the solar quadrupole mass moment, the Keplerian mean motions, the general relativistic Schwarzschild field and the asteroid ring would amount to some tens of percent.

gr-qc↗

arXiv2005

On the impossibility of using certain existing spacecraft for the measurement of the Lense-Thirring effect in the terrestrial gravitational field

In the context of the currently ongoing efforts to improve the accuracy and reliability of the measurement of the Lense-Thirring effect in the gravitational field of the Earth it has recently been proposed to use the data from the existing spacecraft endowed with some active mechanisms of compensation of the non-gravitational accelerations like GRACE. In this paper we critically discuss this interesting possibility. Unfortunately, it turns out to be unpracticable because of the impact of the uncancelled even zonal harmonic coefficients of the multipolar expansion of the terrestrial gravitational potential and of some time-dependent tidal perturbations which would resemble as superimposed linear trends over the necessarily limited observational time span of the analysis.

gr-qc↗

arXiv2005

On a possible new approach for investigating the secular variations of the low-degree geopotential coefficients

In this paper we try to suggest a possible novel method to determine some selected even zonal harmonics J_l of the Earth's geopotential. Time series many years long of suitably linearly combined residuals of some Keplerian orbital elements of certain existing geodetic SLR satellites would be examined. A CHAMP/GRACE-only background reference model should be used for the part of the geopotential which we are not interested in. The retrieved values for the even zonal harmonics of interest would be, by construction, independent of each other and of any post-Newtonian features. The so obtained mini-model could, subsequently, be used in order to enhance the accuracy and the reliability of some tests of post-Newtonian gravity, with particular emphasis to the measurement of the Lense-Thirring effect by means of LAGEOS and LAGEOS II.

physics.geo-ph↗

arXiv2005

Some comments on the recent results about the measurement of the Lense-Thirring effect in the gravitational field of the Earth with the LAGEOS and LAGEOS II satellites

With quantitative numerical simulations we show that the secular variations of the even zonal harmonics of the geopotential do affect the measurement of the Lense-Thirring effect with the nodes of LAGEOS and LAGEOS II at a \sim 14% level. Thus, the 1-sigma total error in the performed test with the 2nd generation CHAMP-only EIGEN2 Earth gravity model amounts to 51%, contrary to 18% claimed by Ciufolini.

gr-qc↗

arXiv2005

On the possibility of testing the Brane-World scenario with orbital motions in the Solar System

Recently it has been suggested to use the perigee of the proposed LARES/WEBER-SAT satellite in order to measure the secular precession which would be induced on such Keplerian orbital element by a weak-field modification of gravity occurring in some Brane-World scenarios put forth by Dvali, Gabadadze and Porrati. This precession, derived for the first time by Lue and Starkman, amounts to 4\times 10-3 milliarcseconds per year for an Earth orbiting satellite. In this paper we show that, according to the recently released EIGEN-CG01C Earth gravity model the quite larger systematic errors due to the Newtonian part of the terrestrial gravitational potential would vanish any attempts to detect a so small effect. The situation is much more favorable in the Solar System scenario. Indeed, the non-Newtonian perihelion advance of Mars, which is the currently best tracked planet, has recently been measured with an accuracy of 1\times 10^-4 arcseconds per century; the Dvali precession is 4\times 10^-4 arcseconds per century. A suitable combination of the perihelia and the nodes of Mars and Mercury, which disentangles the Dvali effect from the competing larger Newtonian and general relativistic precessions, might allow to reach a 1-sigma 47% level of accuracy.

gr-qc↗

arXiv2005

On the reliability of the so far performed tests for measuring the Lense-Thirring effect with the LAGEOS satellites

In this paper we will show in detail that the performed attempts aimed at the detection of the general relativistic Lense-Thirring effect in the gravitational field of the Earth with the existing LAGEOS satellites are often presented in an optimistic and misleading way which is inadequate for such an important test of fundamental physics. E.g., in the latest reported measurement of the gravitomagnetic shift with the nodes of the LAGEOS satellites and the 2nd generation GRACE-only EIGEN-GRACE02S Earth gravity model over an observational time span of 11 years a 5-10% total accuracy is claimed at 1-3sigma, respectively. We will show that, instead, it might be 15-45% (1-3sigma) if the impact of the secular variations of the even zonal harmonics is considered as well.

gr-qc↗