A rotating three component perfect fluid source and its junction with empty space-time

The Kerr solution for empty space-time is presented in an ellipsoidally symmetric coordinate system and it is used to produce generalised ellipsoidal metrics appropriate for the generation of rotating interior solutions of Einstein's equations. It is shown that these solutions are the familiar static perfect fluid cases commonly derived in curvature coordinates but now endowed with rotation. The resulting solutions are also discussed in the context of T-solutions of Einstein's equations and the vacuum T-solution outside a rotating source is presented. The interior source for these solutions is shown not to be a perfect fluid but rather an anisotropic three component perfect fluid for which the energy momentum tensor is derived. The Schwarzschild interior solution is given as an example of the approach.Comment: 14 page

Scattering map for two black holes

We study the motion of light in the gravitational field of two Schwarzschild black holes, making the approximation that they are far apart, so that the motion of light rays in the neighborhood of one black hole can be considered to be the result of the action of each black hole separately. Using this approximation, the dynamics is reduced to a 2-dimensional map, which we study both numerically and analytically. The map is found to be chaotic, with a fractal basin boundary separating the possible outcomes of the orbits (escape or falling into one of the black holes). In the limit of large separation distances, the basin boundary becomes a self-similar Cantor set, and we find that the box-counting dimension decays slowly with the separation distance, following a logarithmic decay law.Comment: 20 pages, 5 figures, uses REVTE

Modelling spectral and timing properties of accreting black holes: the hybrid hot flow paradigm

The general picture that emerged by the end of 1990s from a large set of optical and X-ray, spectral and timing data was that the X-rays are produced in the innermost hot part of the accretion flow, while the optical/infrared (OIR) emission is mainly produced by the irradiated outer thin accretion disc. Recent multiwavelength observations of Galactic black hole transients show that the situation is not so simple. Fast variability in the OIR band, OIR excesses above the thermal emission and a complicated interplay between the X-ray and the OIR light curves imply that the OIR emitting region is much more compact. One of the popular hypotheses is that the jet contributes to the OIR emission and even is responsible for the bulk of the X-rays. However, this scenario is largely ad hoc and is in contradiction with many previously established facts. Alternatively, the hot accretion flow, known to be consistent with the X-ray spectral and timing data, is also a viable candidate to produce the OIR radiation. The hot-flow scenario naturally explains the power-law like OIR spectra, fast OIR variability and its complex relation to the X-rays if the hot flow contains non-thermal electrons (even in energetically negligible quantities), which are required by the presence of the MeV tail in Cyg X-1. The presence of non-thermal electrons also lowers the equilibrium electron temperature in the hot flow model to <100 keV, making it more consistent with observations. Here we argue that any viable model should simultaneously explain a large set of spectral and timing data and show that the hybrid (thermal/non-thermal) hot flow model satisfies most of the constraints.Comment: 26 pages, 13 figures. To be published in the Space Science Reviews and as hard cover in the Space Sciences Series of ISSI - The Physics of Accretion on to Black Holes (Springer Publisher

A White Paper on keV sterile neutrino Dark Matter

We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved—cosmology, astrophysics, nuclear, and particle physics—in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos

Техника хирургического вывиха бедра при лечении больных с юношеским эпифизеолизом головки бедренной кости

Purpose: to evaluate the efficiency of modified Dunn procedure for treatment of severe slipped capital femoral epiphysis.Material and Methods. The authors used the modified Duim procedure for treatment of 6 patients with SCFE aged from 10 to 13 years and displacement degree over 55°. Chronic disease form was reported in one patient, acute displacement along the chronic process was reported in 5 patients. All patients had a stable form of SCFE by Loder classification. Surgical procedure was performed within 6 to 12 months from the onset of disease.Results. Normal anatomical relations in the hip joint were restored in all patients. During follow up from 18 until 48 months the patients did not demonstrate aseptic femoral head necrosis or chondrolysis. Adolescents did not complain on pain or hip motion limitations. Treatment outcomes assessment by Harris hip score was 97 points.Conclusion. Based on outcomes of the modified Durm procedure the authors conclude that the method provides for complete restoration of the anatomical relations between femoral neck and epiphysis and, thus, the hip joint biomechanics. Femur dislocation allows to form an extended flap to ensure epiphysis perfusion which improves overall blood supply in the femoral head and consequently decreases the risk of aseptic necrosis and chondrolysis Цель исследования — оценить эффективность применения модифицированной операции Dunn при лечении тяжелых форм юношеского эпифизеолиза головки бедренной кости.Материал и методы. Модифицированная техника Dunn использована при лечении 6 пациентов с юношеским эпифизеолизом головки бедренной кости (ЮЭГБК) в возрасте от 10 до 13 лет и степенью смещения эпифиза более 55°. У одного пациента была хроническая форма заболевания, у 5 — острый эпифизеолиз на фоне хронического. Все больные имели стабильную форму юношеского эпифизеолиза головки бедренной кости по классификации Loder. Оперативное вмешательство выполняли в сроки от 6 до 12 мес. от начала заболевания. Результаты. У всех больных восстановлены нормальные анатомические взаимоотношения в тазобедренном суставе. В период наблюдения от 1,5 до 4 лет у пациентов не наблюдалось развития асептического некроза головки бедренной кости или хондролиза. Жалоб на боли и ограничение движений в тазобедренном суставе пациенты не предъявляли. Оценка результатов лечения по шкале Harris соответствовала 97 баллам.Заключение. Методика позволяет полностью восстановить анатомические взаимоотношения шейки бедренной кости и эпифиза и, соответственно, биомеханику тазобедренного сустава. Выполнение вывиха бедра позволяет сформировать протяженный питающий эпифиз лоскут, что улучшает кровообращение в головке бедренной кости и значительно снижает риск развития асептического некроза и хондролиза