Black holes with regular horizons in Maxwell-scalar gravity

A class of exact static spherically symmetric solutions of the Einstein-Maxwell gravity coupled to a massless scalar field has been obtained in harmonic coordinates of the Minkowski space-time. For each value of the coupling constant $a$, these solutions are characterized by a set of three parameters, the physical mass $\mu_0$, the electric charge $Q_0$ and the scalar field parameter $k$. We have found that the solutions for both gravitational and electromagneticfields are not only affected by the scalar field, but also the non-trivial coupling with matter constrains the scalar field itself. In particular, we have found that the constant $k$ generically differs from $\pm 1/2$, falling into the interval $|k|\in [0, {1\over2}\sqrt{1+a^2} \hskip 2pt ]$. It takes these values only for black holes or in the case when a scalar field $\phi$ is totally decoupled from the matter. Our results differ from those previously obtained in that the presence of arbitrary coupling constant $a$ gives an opportunity to rule out the non-physica horizons. In one of the special cases, the obtained solution corresponds to a charged dilatonic black hole with only one horizon $\mu_+$ and hence for the Kaluza-Klein case. The most remarkable property of this result is that the metric, the scalar curvature, and both electromagnetic and scalar fields are all regular on this surface. Moreover, while studying the dilaton charge, we found that the inclusion of the scalar field in the theory result in a contraction of the horizon. The behavior of the scalar curvature was analyzed.Comment: 19 pages, LaTex, no figure

Study of the Pioneer Anomaly: A Problem Set

Analysis of the radio-metric tracking data from the Pioneer 10 and 11 spacecraft at distances between 20--70 astronomical units from the Sun has consistently indicated the presence of an anomalous, small, and constant Doppler frequency drift. The drift is a blue-shift, uniformly changing at the rate of (5.99 +/- 0.01) x 10^{-9} Hz/s. The signal also can be interpreted as a constant acceleration of each particular spacecraft of (8.74 +/- 1.33) x 10^{-8} cm/s^2 directed toward the Sun. This interpretation has become known as the Pioneer anomaly. We provide a problem set based on the detailed investigation of this anomaly, the nature of which remains unexplained.Comment: 14 pages, 3 figures, 5 tables, minor corrections before publicatio

Relativistic gravitational deflection of light and its impact on the modeling accuracy for the Space Interferometry Mission

We study the impact of relativistic gravitational deflection of light on the accuracy of future Space Interferometry Mission (SIM). We estimate the deflection angles caused by the monopole, quadrupole and octupole components of gravitational fields for a number of celestial bodies in the solar system. We observe that, in many cases, the magnitude of the corresponding effects is significantly larger than the 1 uas accuracy expected from SIM. This fact argues for the development of a relativistic observational model for the mission that would account for the influence of both static and time-varying effects of gravity on light propagation. Results presented here are different from the ones obtained elsewhere by the fact that we specifically account for the differential nature of the future SIM astrometric measurements. We also obtain an estimate for the accuracy of possible determination of the Eddington's parameter \gamma via SIM global astrometric campaign; we conclude that accuracy of ~7 x 10^{-6} is achievable via measurements of deflection of light by solar gravity.Comment: revtex4, 20 pages, 9 figures, 13 table