Galaxy rotation curves. The theory

The non-gauge vector field with as simple as possible Lagrangian (\ref{Lagrangian}) turned out an adequate tool for macroscopic description of the main properties of dark matter. The dependence of the velocity of a star on the radius of the orbit $V\left(r\right)$ -- galaxy rotation curve -- is derived analytically from the first principles\ completely within the Einstein's general relativity. The Milgrom's empirical modification of Newtonian dynamics in nonrelativistic limit (MOND) gets justified and specified in detail. In particular, the transition to a plateau is accompanied by damping oscillations. In the scale of a galaxy, and in the scale of the whole universe, the dark matter is described by a vector field with the same energy-momentum tensor. It is the evidence of the common physical nature. Now, when we have the general expression (\ref{Tik b=c=0}) for the energy-momentum tensor of dark matter, it is possible to analyze its influence on the structure and evolution of super heavy stars and black holes.Comment: 17 pages, 13 figure

A photon breeding mechanism for the high-energy emission of relativistic jets

We propose a straightforward and efficient mechanism for the high-energy emission of relativistic astrophysical jets associated with an exchange of interacting high-energy photons between the jet and the external environment. Physical processes playing the main role in this mechanism are electron-positron pair production by photons and the inverse Compton scattering. This scenario has been studied analytically as well as with numerical simulations demonstrating that a relativistic jet (with the Lorentz factor larger than 3--4) moving through the sufficiently dense, soft radiation field inevitably undergoes transformation into a luminous state. The process has a supercritical character: the high-energy photons breed exponentially being fed directly by the bulk kinetic energy of the jet. Eventually particles feed back on the fluid dynamics and the jet partially decelerates. As a result, a significant fraction (at least 20 per cent) of the jet kinetic energy is converted into radiation mainly in the MeV -- GeV energy range. The mechanism maybe responsible for the bulk of the emission of relativistic jets in active galactic nuclei, microquasars and gamma-ray bursts.Comment: 10 pages, 9 figures; MNRAS, in pres

The mystery of spectral breaks: Lyman continuum absorption by photon-photon pair production in the Fermi GeV spectra of bright blazars

We reanalyze Fermi/LAT gamma-ray spectra of bright blazars with a higher photon statistics than in previous works and with new Pass 7 data representation. In the spectra of the brightest blazar 3C 454.3 and possibly of 4C +21.35 we detect breaks at 5 GeV (in the rest frame) associated with the photon-photon pair production absorption by He II Lyman continuum (LyC). We also detect confident breaks at 20 GeV associated with hydrogen LyC both in the individual spectra and in the stacked redshift-corrected spectrum of several bright blazars. The detected breaks in the stacked spectra univocally prove that they are associated with atomic ultraviolet emission features of the quasar broad-line region (BLR). The dominance of the absorption by hydrogen Ly complex over He II, rather small detected optical depth, and the break energy consistent with the head-on collisions with LyC photons imply that the gamma-ray emission site is located within the BLR, but most of the BLR emission comes from a flat disk-like structure producing little opacity. Alternatively, the LyC emission region size might be larger than the BLR size measured from reverberation mapping, and/or the gamma-ray emitting region is extended. These solutions would resolve a long-standing issue how the multi-hundred GeV photons can escape from the emission zone without being absorbed by softer photons.Comment: 7 pages, 6 figures; accepted to Ap

Research, Extension, and Information: Key Inputs in Agricultural Productivity Growth

The objective of this paper is to examine how economists have perceived the contributions of agriculture to the economic development process and then to present the case for the critical role that research, extension, and information can play in agricultural productivity growth and thus in economic development, particularly in low income countries. After a brief presentation of the framework commonly used to examine productivity growth, a distinction is made between technological change and technical efficiency. This distinction is crucial for policy purposes because the major impetus behind technological change are research and development, while education and experience are critical to improving managerial capabilities to make efficient use of a given technology. Empirical findings concerning the returns on agricultural research, with special attention to studies that have focused on Pakistan, are discussed. The paper then offers an overview of alternative methodologies available to measure technical efficiency, summarises the empirical literature, and finally focuses on studies dealing with Pakistani agriculture. Once it is established that improvements in technical efficiency could contribute significantly to increases in farm output and income, the discussion moves to some issues that have implications for the measurement and potential improvement of farm efficiency. An overview of a model of privatised extension services, currently being applied in some Latin American countries and which could have some relevance to conditions in Pakistan and elsewhere, is provided. The paper ends with the contention that significant improvements are needed in the collection and organisation of farm production data if we are to advance our understanding of the drivers of productivity growth at the farm level