Narrow Results

Outstanding questions in the study of relativistic jets in their various astrophysical settings are discussed in the context of a general dynamical model.

In the presence of rotation, gravity induces, even at zero temperature, a chiral vortical current. This current is interpreted as emerging from the gravitational Chern–Simons current. We argue that this gravitational Chern–Simons chiral vortical current may provide a novel universal microscopic mechanism behind the generation of collimated jets from rotating astrophysical compact sources.

A laboratory simulation of astrophysical processes is one of the intensively developed areas of plasma physics. A new series of experiments has been launched recently on the plasma focus type facility in NRC Kurchatov Institute. The main goal is to study the mechanisms of the jet stabilization, due to which it can propagate at distances much greater than their transverse dimensions. The experiments with stationary gas filling revealed regimes in which a narrowly collimated plasma jet was formed, the head of which was no wider than several centimeters at jet propagation distances of up to 100cm. The PF-1000 (IFPiLM, Warsaw, Poland) and KPF-4 (SFTI, Sukhum, Abkhazia) experiments are aimed at creating profiled initial gas distributions to control the conditions of plasma jet propagation in the ambient plasma. Estimations of the dimensionless parameters, i.e. the Mach, Reynolds and Peclet numbers which were achieved during the experiments, showed that the PF-facilities can be used for the YSO jets modeling. The future experiments, which can allow one to understand the nature of the stable plasma ejections observed in many astrophysical sources, are discussed.

It has been suggested that single and double jets observed emanating from certain astrophysical objects may have a purely gravitational origin. We discuss new classes of pulsed gravitational wave solutions to the equation for perturbations of Ricci-flat spacetimes around Minkowski metrics, as models for the genesis of such phenomena. We discuss how these solutions are motivated by the analytic structure of spatially compact finite energy pulse solutions of the source-free Maxwell equations generated from complex chiral eigen-modes of a chirality operator. Complex gravitational pulse solutions to the linearized source-free Einstein equations are classified in terms of their chirality and generate a family of non-stationary real spacetime metrics. Particular members of these families are used as backgrounds in analyzing time-like solutions to the geodesic equation for test particles. They are found numerically to exhibit both single and double jet-like features with dimensionless aspect ratios suggesting that it may be profitable to include such backgrounds in simulations of astrophysical jet dynamics from rotating accretion discs involving electromagnetic fields.

An accretion disk around a supermassive black hole may be strongly perturbed by the presence of a secondary black hole. Recent simulations have shown that, under certain conditions, the tidal torques exerted by the secondary black hole may open an annular gap in the disk. In this regime, matter "overflows" across the secondary's orbit to accrete onto the primary and may feed a pair of relativistic jets.

In this work we study the radiative properties of a binary system of supermassive black holes, assuming that a relativistic jet is launched from the primary and the migration of the secondary across the disk proceeds in the "overflowing" regime. The modified radiative spectrum of the disk is calculated accounting for strong gravitational effects in the innermost region. The jet emits non-thermal radiation all along the electromagnetic spectrum by interaction of locally accelerated electrons with the jet's magnetic field and internal and external radiation. In particular, we investigate whether the interaction of the relativistic electrons with the photons emitted by the accretion disk induces any signature in the spectral energy distribution of the jet that may reveal the presence of the secondary black hole.

We study the production of neutrons in the corona of an accreting black hole through the interaction of locally accelerated protons with matter and radiation. A fraction of these neutrons may escape and penetrate into the base of the jet, later decaying into protons. This is a possible mechanism for loading Poynting-dominated outflows with baryons.

We characterize the spatial and energy distribution of neutrons in the corona and that of the protons injected in the jet by neutron decay. We assess the contribution of these protons to the radiative spectrum of the jet. We also investigate the fate of the neutrons that escape the corona into the external medium.

Under the action of field intensities around the Schwinger critical field, a dense electron gas behaves as unidimensional, exerting strong pressure along the applied field. We suggest a model for maintaining the magnetic field self-consistently, by assuming spin parallel pairing leading to a partial bosonization of the electron gas, which is described by a charged vector boson field, able to experience condensation, leading to a ferromagnetic behavior. Our aim is to suggest a possible quantum relativistic self-magnetized jet model. High frequency photons will be deviated also along paths parallel to the external field, leading to a model for a jet. Any addition of matter and/or energy to the electron system, would contribute to increase the kinetic energy along the magnetic field axis, an the jet may extend for long distances.

Even if one would assume the astrophysical massive compact objects (MCOs) to be Black Holes (BHs), no energy can be extracted from them because neutral vacuum BHs cannot acquire any (induced) electromagnetic property, neither can any current emerge from the central singularity. This is so despite wishful models claiming the contrary by attributing the Event Horizon (EH) or an imaginary “membrane” with wishful electromagnetic properties. Similarly various Quantum Gravity (QG) theories too attribute various imaginary and mysterious properties like “Brick Wall”, “Fire Wall” with the EH even after claiming that the vacuum EH is a perfectly regular spacetime without any special property! The vacuum EH is also associated with imaginary material structures and entropy in a completely self-contradictory manner. To legitimize such contradictions & fudge, the “Holography” principle is invoked by which the information contained within the 3-D BH interior is hypothesized to be encoded on the 2-D EH. Further, some QG theories try to explain gravity & BH entropy (S_BH) in terms of random motion of “atoms of vacuum” of dimension ~ ℓ_p (Planck Length). But since ℓ_p → 0 as ħ → 0, a classical vacuum would possess infinite entropy by such a hypothesis and so spacetime may not be granular ever. It is asserted that though BHs correspond to exact General Relativistic solutions, the relevant integration constants are zero, i.e., a Schwarzschild BH has M = 0 (Mitra, JMP 2009), and Kerr BHs too correspond to M = a = 0, implying S_BH = 0 & BHs are asymptotic ground states of preceding collapse which radiates away entire mass-energy, angular momentum & entropy. Thus the finite mass BH Candidates must be Quasi-BHs. It has been shown that the most natural case for Quasi BHs are ultra-magnetized hot quasi-static balls of plasma, Magnetospheric Eternally Collapsing Objects (MECOs) radiating at their Eddington Luminosity. Spinning MECOs behave like ultramagatic GR pulsars and may naturally explain high energy astrophysical phenomena. Since there is no true BH, there no quantum “Information Paradox”, no need for “Holography”, no need to bid farewell to physical reality. As spactime membrane gets infinitely stretched and no singularity is formed, there is probably no need for any fictitious QG. Gravity may always remain classical and separated from other interactions like oil & water.