We use covariant techniques to examine the implications of the dynamical equivalence between geodesic motions and adiabatic hydrodynamic flows. Assuming that the metrics of a geodesically and a non-geodesically moving fluid are conformally related, we calculate and compare their mass densities. The density difference is then expressed in terms of the fundamental physical quantities of the fluid...

Current, accumulating evidence for (mildly) relativistic blueand red-shifted absorption lines in AGNs is reviewed. XMM-Newton and Chandra sensitive X-ray observations are starting to probe not only the kinematics (velocity) but also the dynamics (accelerations) of highly ionized gas flowing in-and-out from, likely, a few gravitational radii from the black hole. It is thus emphasized that X-ray ...

The paper describes a new upwind conservative numerical scheme for special relativistic resistive magnetohydrodynamics with scalar resistivity. The magnetic field is kept approximately divergence free and the divergence of the electric field consistent with the electric charge distribution via the method of Generalized Lagrange Multiplier. The hyperbolic fluxes are computed using the HLL prescr...

The transport of photons in steady, spherical, scattering flows is investigated. The moment equations are solved analytically for accretion onto a Schwarzschild black hole, taking into full account relativistic effects. We show that the emergent radiation spectrum is a power law at high frequencies with a spectral index smaller (harder spectrum) than in the non–relativistic case. Radiative tran...

In this lecture I give an introduction to the rotational energy extraction of black holes by the electromagnetic Blandford-Znajek process and the generation of relativistic jets. After some basic material on the electrodynamics of black hole magnetospheres, we derive the most important results of Blandford and Znajek by making use of Kerr-Schild coordinates, which are regular on the horizon. In...

A new code and methodology are introduced for solving the general relativistic magnetohydrodynamic (GRMHD) equations in fixed background spacetimes using time-explicit, finitevolume discretization. The code has options for solving the GRMHD equations using traditional artificial-viscosity (AV) or non-oscillatory central difference (NOCD) methods, or a new extended AV (eAV) scheme using artifici...

The peak of the de-absorbed energy distribution of the TeV emitting blazars, all of the BL Lacertae (BL) class, can reach values up to ∼ 10 TeV. In the context of synchrotron-self Compton (SSC) models of relativistic uniformly moving blobs of plasma, such high energy peak emission can be reproduced only by assuming Doppler factors of δ ∼ 50. However, such high values strongly disagree with the ...