A first-order perturbation theory exists for the flyby problem with the Born approximation as the reference orbit (J. D. Anderson and G. Giampieri 1999, Icarus 138, 309–318, AG thereafter). This theory is applicable when the deflection parameter μ/bv2 (where μ is the product of the gravitational constant by the body’s mass, b the impact parameter, and v the velocity of the flyby) is small. Here...

Here we estimate the magnitude of the signals expected for realistic cosmic neutrino backgrounds in detectors attempting to measure the mechanical forces exerted on macroscopic targets by the elastic scattering of relic neutrinos. We study effects proportional to the weak coupling constant GF and to G 2 F for Dirac and Majorana neutrinos, either relativistic or non-relativistic, both gravitatio...

Introduction. – In [1] the authors claim to observe a periodic signal in measurements of Newton’s gravitational constant, G. Specifically they find a 5.9-year-period signal that is strongly correlated with variations in the observed length of day [2]. They do not suggest that G actually varies on these time scales, but rather that there could be some systematic effect on the measurement process...

Using the recently upgraded Long Baseline Array, we have measured the trigonometric parallax of PSR J0437–4715 to better than 1% precision, the most precise pulsar distance determination made to date. Comparing this VLBI distance measurement to the kinematic distance obtained from pulsar timing, which is calculated from the pulsar’s proper motion and apparent rate of change of orbital period, g...

The equations which determine the response of a charged particle moving in a magnetic field to an incident gravitational wave(GW) are derived in the linearized approximation to general relativity. We briefly discuss several astrophysical applications of the derived formulae taking into account the resonance between the wave and the particle’s motion which occurs at ωg = 2Ω, whenever the GW is p...

We study the Kaluza-Klein zero modes of massless bulk fields with various spins in the background of dilatonic and self-tuning flat domain walls. We find that the zero modes of all the massless bulk fields in such domain wall backgrounds are normalizable, unlike those in the background of the non-dilatonic domain wall with infinite extra space of Randall and Sundrum. In particular, gravity in t...

A covariant scalar-tensor-vector gravity theory is developed which allows the gravitational constant G, a vector field coupling ω and the vector field mass μ to vary with space and time. The equations of motion for a test particle lead to a modified gravitational acceleration law that can fit galaxy rotation curves and cluster data without non-baryonic dark matter. The theory is consistent with...

A hypothetical time-variation of the gravitational constant G would make neutron stars expand or contract, so the matter in their interiors would depart from beta equilibrium. This induces non-equilibrium weak reactions, which release energy that is invested partly in neutrino emission and partly in internal heating. Eventually, the star arrives at a stationary state in which the temperature re...

A new formulation of Carter’s constant for geodesic motion in Kerr black holes is given. It is shown that Carter’s constant corresponds to the total angular momentum plus a precisely defined part which is quadratic in the linear momenta. The characterization is exact in the weak field limit obtained by letting the gravitational constant go to zero. It is suggested that the new form can be usefu...

Various aspects of the C-metric representing two rotating charged black holes accelerated in opposite directions are summarized and its limits are considered. A particular attention is paid to the special-relativistic limit in which the electromagnetic field becomes the “magic field” of two oppositely accelerated rotating charged relativistic discs. When the acceleration vanishes the usual elec...