Narrow Results

Gravitational microlensing is a powerful method to constrain the abundance of massive dark objects in the Milky Way halo. We calculate the optical depth and the microlensing rate for events caused by Primordial Black Holes (PBHs) eventually distributed in the Milky Way halo, towards some selected directions of observation, as the Galactic bulge, the Large and the Small Magellanic Clouds and the M31 galaxy. The capability of the Euclid space telescope to constraint the abundance of PBHs with mass ≥ 10⁻⁷M_⊙ in observation towards the Galactic bulge is also discussed.

We present here the proposal to use the LISA interferometer for detecting the gravitomagnetic field due to the rotation of the Milky Way, including the contribution given by the dark matter halo. The galactic signal would be superposed to the gravitomagnetic field of the Sun. The technique to be used is based on the asymmetric propagation of light along the closed contour of the space interferometer (Sagnac-like approach). Both principle and practical aspects of the proposed experiment are discussed. The strategy for disentangling the sought for signal from the kinematic terms due to proper rotation and orbital motion is based on the time modulation of the time of flight asymmetry. Such modulation will be originated by the annual oscillation of the plane of the interferometer with respect to the galactic plane. Also the effect of the gravitomagnetic field on the polarization of the electromagnetic signals is presented as an in principle detectable phenomenon.

An exact model in Einstein-Maxwell gravity describing a magnetized galactic disk-halo system is presented. The description of properties of the stationary metric and its source are discussed. All the expressions are presented in terms of an Harmonic function. A “generalization” of the Kuzmin potential is used as a particular example. The solution obtained is asymptotically Minkowskian in general and turns out to be singularity free. All the relevant quantities show a reasonable physical behavior.