Black holes as antimatter factories

We consider accretion of matter onto a low mass black hole surrounded by ionized medium. We show that, because of higher mobility of protons than electrons, the black hole would acquire positive electric charge. If the black hole's mass is about or below $10^{20}$ g, the electric field at the horizon can reach the critical value which leads to vacuum instability and electron--positron pair production by the Schwinger mechanism. Since the positrons are ejected by the emergent electric field, while electrons are back--captured, the black hole operates as an antimatter factory which effectively converts protons into positrons.Comment: 5 pages, no figure. v2: with discussion section not included in the refereed versio

The Calculation of the Spatial Distribution of Temperature Fields for Remote Monitoring of the Surface From an Unmanned Aerial Vehicle

В статье рассматривается расчет пространственного распределения температурных полей на поверхности и вглубь грунта. Представлена общая постановка задачи расчета пространственного распределения температурных полей в переменно-насыщенных пористых средах. Приведены результаты реализации предложенного способа расчета в ходе натурного экспериментаThe article deals with the calculation of the spatial distribution of temperature fields on the surface and deep into the soil. Presents a general formulation of the problem of calculating the spatial distribution of temperature fields in variably-saturated porous media. The results of the proposed method of calculation in the field experimen

Searching for super-WIMPs in leptonic heavy meson decays

We study constraints on the models of bosonic super-weakly interacting particle (super-WIMP) dark matter (DM) with DM masses $m_X \sim \mathcal{O}(1 - 100)$ keV from leptonic decays $M\rightarrow \ell \bar{\nu}_\ell + X$, where $M=B^\pm, D^\pm, D_s^\pm$ is a heavy meson state. We focus on two cases where $X$ denotes either a light pseudoscalar (axion-like), or a light vector state that couples to the standard model (SM) through kinetic mixing. We note that for a small DM mass these decays are separately sensitive to DM couplings to quarks, but not its mass.Comment: 17 pages, 3 figures, 6 table

Methods of Assessment of Dynamics of Change of Probability Characteristics of Recognition of Objects in Aerial Reconnaissance

В статье представлена методика оценки динамики изменения вероятностных характеристик распознавания и различения объектов воздушной разведки при операторном и автоматическом дешифрировании соответственно. Представлена математическая постановка задачи распознавания объектов воздушной разведки по инфракрасным изображениям. Приведены результаты оценки изменения вероятностных характеристик распознавания (различения) объектов воздушной разведки по результатам натурного экспериментаThe article presents a method of assessing the dynamics of changes in the probabilistic characteristics of recognition and distinction of objects of aerial reconnaissance in the operator and automatic decryption, respectively. The mathematical formulation of the problem of recognition of objects of aerial reconnaissance by infrared images is presented. The results of the evaluation of changes in the probabilistic characteristics of recognition (distinction) of objects of aerial reconnaissance on the results of full-scale experimen

Primordial black holes and the observed Galactic 511 keV line

The observed 511 keV line from the Galactic Bulge is a real challenge for theoretical astrophysics: despite a lot of suggested mechanisms, there is still no convincing explanation and the origin of the annihilated positrons remains unknown. Here we discuss the possibility that a population of slowly evaporating primordial black holes with the mass around $10^{16}-10^{17}$ g ejects (among other particles) low--energy positrons into the Galaxy. In addition to positrons, we have also calculated the spectrum and number density of photons and neutrinos produced by such black holes and found that the photons are potentially observable in the near future, while the neutrino flux is too weak and below the terrestrial and extra--terrestrial backgrounds. Depending on their mass distribution, such black holes could make a small fraction or the whole cosmological dark matter.Comment: 7 pages, 7 figures. v4: refereed version + erratu

Thermal production of relativistic Majorana neutrinos: Strong enhancement by multiple soft scattering

The production rate of heavy Majorana neutrinos is relevant for models of thermal leptogenesis in the early Universe. In the high temperature limit the production can proceed via the 1 2 (inverse) decays which are allowed by the thermal masses. We consider new production mechanisms which are obtained by including additional soft gauge interactions with the plasma. We show that an arbitrary number of such interactions gives leading order contributions, and we sum all of them. The rate turns out to be smooth in the region where the 1 2 processes are kinematically forbidden. At higher temperature it is enhanced by a factor 3 compared to the 1 2 rate.Comment: 26 pages, 8 figures; added references, added comments on 2 to 2 scattering processes, improved appearance of fig. 8, corrected typos; matches published versio

A lower bound on the mass of Dark Matter particles

We discuss the bounds on the mass of Dark Matter (DM) particles, coming from the analysis of DM phase-space distribution in dwarf spheroidal galaxies (dSphs). After reviewing the existing approaches, we choose two methods to derive such a bound. The first one depends on the information about the current phase space distribution of DM particles only, while the second one uses both the initial and final distributions. We discuss the recent data on dSphs as well as astronomical uncertainties in relevant parameters. As an application, we present lower bounds on the mass of DM particles, coming from various dSphs, using both methods. The model-independent bound holds for any type of fermionic DM. Stronger, model-dependent bounds are quoted for several DM models (thermal relics, non-resonantly and resonantly produced sterile neutrinos, etc.). The latter bounds rely on the assumption that baryonic feedback cannot significantly increase the maximum of a distribution function of DM particles. For the scenario in which all the DM is made of sterile neutrinos produced via non-resonant mixing with the active neutrinos (NRP) this gives m_nrp > 1.7 keV. Combining these results in their most conservative form with the X-ray bounds of DM decay lines, we conclude that the NRP scenario remains allowed in a very narrow parameter window only. This conclusion is independent of the results of the Lyman-alpha analysis. The DM model in which sterile neutrinos are resonantly produced in the presence of lepton asymmetry remains viable. Within the minimal neutrino extension of the Standard Model (the nuMSM), both mass and the mixing angle of the DM sterile neutrino are bounded from above and below, which suggests the possibility for its experimental search.Comment: 20 pages, published in JCA

Cold dark matter from heavy right-handed neutrino mixing

We show that, within the see-saw mechanism, an almost decoupled RH neutrino species NDM with mass MDM >~ 100 GeV can play the role of Dark Matter (DM). The NDM's can be produced from non-adiabatic conversions of thermalized (source) RH neutrinos with mass MS lower than MDM. This is possible if a non-renormalizable operator is added to the minimal type I see-saw lagrangian. The observed DM abundance can be reproduced for MDM Δ1/4 ~ 10-13 Λeff ξ, where Λeff is a very high energy new physics scale, δ ≡ (MDM - MS)/MDM and ξ <~ 1 is a parameter determined by the RH neutrino couplings

The Computer Model and the Algorithm of Designing a Target Environment of Remote Monitoring Areas Using Thermal Tomograms with Account of their Geographical Location and Meteorological Conditions

В статье рассматриваются компьютерная модель и алгоритм построения фоноцелевой обстановки на основе экстраполяции температурных полей районов дистанционного мониторинга по базам данных тепловых томограмм объектов-аналогов, подстилающих поверхностей, географического положения и метеорологических условий. Представлена математическая постановка задачи моделирования температурных полей «объектов-аналогов» и подстилающих поверхностей районов дистанционного мониторинга по их тепловым томограммам. Приведены результаты компьютерного моделирования пространственного распределения температурных полей района дистанционного мониторинга по результатам натурного экспериментаThe article considers a computer model and an algorithm used for designing a target environment based on extrapolation of temperature fields of remote monitoring areas according to databases of thermal tomograms of analog objects, underlying surfaces, geographical location and meteorological conditions. A mathematical statement of the problem, concerning simulating the temperature fields of “analogue objects” and bottoming surfaces of remote monitoring areas by means of their thermal tomograms, is described. The outcomes of computer simulation of the spatial distribution of temperature fields of the remote monitoring area based on the results of the field experiment are presente