Stellar binaries in galactic nuclei: tidally stimulated mergers followed by tidal disruptions

We investigate interactions of stellar binaries in galactic nuclear clusters with a massive black hole (MBH). We consider binaries on highly eccentric orbits around the MBH that change due to random gravitational interactions with other stars in the nuclear stellar cluster. The pericenters of the orbits perform a random walk, and we consider cases where this random walk slowly brings the binary to the Hills tidal separation radius (the so-called empty loss-cone regime). However, we find that in a majority of cases the expected separation does not occur and instead the members of the binary merge together. This happens because the binary's eccentricity is excited by tidal interactions with the MBH, and the relative excursions of the internal eccentricity of the binary far exceed those in its internal semimajor axis. This frequently reduces the pericenter separation to values below typical stellar diameters, which induces a significant fraction of such binaries to merge ($\gtrsim 75\%$ in our set of numerical experiments). Stellar tides do not appreciably change the total rate of mergers but circularise binaries, leading to a significant fraction of low-eccentricity, low-impact-velocity mergers. Some of the stellar merger products will then be tidally disrupted by the MBH within $\sim 10^6$ years. If the merger strongly enhances the magnetic field of the merger product, this process could explain observations of prompt relativistic jet formation in some tidal disruption events

Public-Private Partnership in der Russischen Föderation: Aktuelle Entwicklungen und Tendenzen im Kontext der Wirtschaftskrise

Seit mehreren Jahren wird in der Russischen Föderation der Versuch unternommen, alternative staatliche Beschaffungsinstrumente zu implementieren, die auf einer Kooperation mit privaten Strukturen beruhen. Im folgenden Beitrag wird neben einer allgemeinen definitorischen Einleitung zum einen die historische Entwicklung der Institution des Public-Private Partnershipsin der Russischen Föderation nachgezeichnet, sowie zum anderen die These vertreten, dass die aktuelle Wirtschaftskrise auch eine Chance für die verschiedenen Kooperationsformen bedeutet

Zcipher Algorithm Specification

This paper describes the Zcipher - a symmetric encryption/decryption cryptographic algorithm, designed to be secure and high-performance with small memory footprint and simple structure

Hybrid computer system programming technology with adaptation and scaling of calculations

The paper considers the programming technology for hybrid computer systems, which contain reconfigurable and microprocessor computational nodes. The base of the programming technology for hybrid computer systems is the high-level programming language COLAMO with extensions, which allow descriptions of various types of parallel calculations such as structural, structural-procedural, multi-procedural and procedural forms of organization of calculations in a unified parallel-pipeline form. The suggested parallel-pipeline form allows modifications of forms of organization of calculations. Such modifications are performed automatically by the COLAMO language preprocessor, which takes into account current configuration of the hybrid computer system. Owing to the suggested technology, the program can be automatically adapted to the changed architecture or configuration of the hybrid computer system without any modifications of the source code made by the developer. Specially for this the source parallel program, developed in the programming language COLAMO, is transformed by the pre-processor into the canonical form. Then the pre-processor estimates the available computational resource, detects effective parameters of implementation of the program on the available resource and, if necessary, reduces the program performance to adapt it to the current configuration of the hybrid computer system. The technology provides two-way scaling: for increasing of the available computational resource (induction), and for reducing of the available computational resource (reduction), which provides resource independence of programming during implementation of the program, i.e. the developer is not “bound” to the available hardware resource of the computer system