Collisions and drag in debris discs with eccentric parent belts

Context: High-resolution images of circumstellar debris discs reveal off-centred rings that indicate past or ongoing perturbation, possibly caused by secular gravitational interaction with unseen stellar or substellar companions. The purely dynamical aspects of this departure from radial symmetry are well understood. However, the observed dust is subject to additional forces and effects, most notably collisions and drag. Aims: To complement the studies of dynamics, we therefore aim to understand how new asymmetries are created by the addition of collisional evolution and drag forces, and existing ones strengthened or overridden. Methods: We augmented our existing numerical code "Analysis of Collisional Evolution" (ACE) by an azimuthal dimension, the longitude of periapse. A set of fiducial discs with global eccentricities ranging from 0 to 0.4 is evolved over giga-year timescales. Size distribution and spatial variation of dust are analysed and interpreted. The basic impact of belt eccentricity on spectral energy distributions (SEDs) and images is discussed. Results: We find features imposed on characteristic timescales. First, radiation pressure defines size cutoffs that differ between periapse and apoapse, resulting in an asymmetric halo. The differences in size distribution make the observable asymmetry of the halo depend on wavelength. Second, collisional equilibrium prefers smaller grains on the apastron side of the parent belt, reducing the effect of pericentre glow and the overall asymmetry. Third, Poynting-Robertson drag fills the region interior to an eccentric belt such that the apastron side is more tenuous. Interpretation and prediction of the appearance in scattered light is problematic when spatial and size distribution are coupled.Comment: Accepted for publication in A&A, 14 pages, 16 figure

Twisted debris: how differential secular perturbations shape debris disks

Resolved images suggest that asymmetric structures are a common feature of cold debris disks. While planets close to these disks are rarely detected, their hidden presence and gravitational perturbations provide plausible explanations for some of these features. To put constraints on the properties of yet undetected planetary companions, we aim to predict what features such a planet imprints in debris disks undergoing continuous collisional evolution. We discuss the basic equations, analytic approximations and timescales governing collisions, radiation pressure and secular perturbations. In addition, we combine our numerical model of the collisional evolution of the size and spatial distributions in debris disks with the gravitational perturbation by a single planet. We find that the distributions of orbital elements in the disks are strongly dependent on grain sizes. Secular precession is differential with respect to involved semi-major axes and grain sizes. This leads to observable differences between the big grains tracing the parent belt and the small grains in the trailing halo. Observations at different wavelengths can be used to constrain the properties of a possible planet.Comment: 12 pages, 7 figure

Experimental One-Way Quantum Computing

Standard quantum computation is based on sequences of unitary quantum logic gates which process qubits. The one-way quantum computer proposed by Raussendorf and Briegel is entirely different. It has changed our understanding of the requirements for quantum computation and more generally how we think about quantum physics. This new model requires qubits to be initialized in a highly-entangled cluster state. From this point, the quantum computation proceeds by a sequence of single-qubit measurements with classical feedforward of their outcomes. Because of the essential role of measurement a one-way quantum computer is irreversible. In the one-way quantum computer the order and choices of measurements determine the algorithm computed. We have experimentally realized four-qubit cluster states encoded into the polarization state of four photons. We fully characterize the quantum state by implementing the first experimental four-qubit quantum state tomography. Using this cluster state we demonstrate the feasibility of one-way quantum computing through a universal set of one- and two-qubit operations. Finally, our implementation of Grover's search algorithm demonstrates that one-way quantum computation is ideally suited for such tasks.Comment: 36 pages, 6 figures, 2 table

Rare and New Minerals of the Tashelga-Maizaskaya Zone of Gornaya Shoriya, Their Peculiarities and Nature

Rare and new minerals (tashelgite, mukhinite, hibonite, goldmanite and others) discovered in the process of geological studies of the 20th and the 21st centuries in the carbonate stratum of the Tashelga polymetamorphic complex (R3-Rz3ts) composing the graben-syncline structure within the Kuznetsk- Alatau shear zone in Gornaya Shoriya are described. It is shown that the unique mineralization of skarnoids, calciphyres and metasomatites of the district is preconditioned by the processes of metamorphism and further metasomatosis of original carbonate marine sediments contaminated by laterite metabasite weathering products. The impact of the basic rock chemistry on the whole further polychronic endogenous rock mineralization is traced even in such relatively closed systems of the zone as granite pegmatites.Рассмотрены редкие и новые минералы (ташелгит, мухинит, хибонит, голдманит и др.), обнаруженные в ходе геологических исследований XX и XXI веков в карбонатной толще Ташелгинского полиметаморфического комплекса (R3-Rz3ts), слагающего грабен- синклинальную структуру в пределах Кузнецко-Алатаусской сдвиговой зоны Горной Шории. Показано, что уникальная минерализация скарноидов, кальцифиров и метасоматитов района обусловлена процессами метаморфизма и последующего метасоматоза исходных карбонатных морских осадков, загрязненных латеритными продуктами выветривания метабазитов. Установлено влияние химизма исходных пород на всю последующую полихронную эндогенную минерализацию, даже в таких относительно замкнутых системах, каковыми являются гранитные пегматиты района

Rare and New Minerals of the Tashelga-Maizaskaya Zone of Gornaya Shoriya, Their Peculiarities and Nature

Rare and new minerals (tashelgite, mukhinite, hibonite, goldmanite and others) discovered in the process of geological studies of the 20th and the 21st centuries in the carbonate stratum of the Tashelga polymetamorphic complex (R3-Rz3ts) composing the graben-syncline structure within the Kuznetsk- Alatau shear zone in Gornaya Shoriya are described. It is shown that the unique mineralization of skarnoids, calciphyres and metasomatites of the district is preconditioned by the processes of metamorphism and further metasomatosis of original carbonate marine sediments contaminated by laterite metabasite weathering products. The impact of the basic rock chemistry on the whole further polychronic endogenous rock mineralization is traced even in such relatively closed systems of the zone as granite pegmatites.Рассмотрены редкие и новые минералы (ташелгит, мухинит, хибонит, голдманит и др.), обнаруженные в ходе геологических исследований XX и XXI веков в карбонатной толще Ташелгинского полиметаморфического комплекса (R3-Rz3ts), слагающего грабен- синклинальную структуру в пределах Кузнецко-Алатаусской сдвиговой зоны Горной Шории. Показано, что уникальная минерализация скарноидов, кальцифиров и метасоматитов района обусловлена процессами метаморфизма и последующего метасоматоза исходных карбонатных морских осадков, загрязненных латеритными продуктами выветривания метабазитов. Установлено влияние химизма исходных пород на всю последующую полихронную эндогенную минерализацию, даже в таких относительно замкнутых системах, каковыми являются гранитные пегматиты района

Swarm Intelligence and cyber-physical systems: Concepts, challenges and future trends

Swarm Intelligence (SI) is a popular multi-agent framework that has been originally inspired by swarm behaviors observed in natural systems, such as ant and bee colonies. In a system designed after swarm intelligence, each agent acts autonomously, reacts on dynamic inputs, and, implicitly or explicitly, works collaboratively with other swarm members without a central control. The system as a whole is expected to exhibit global patterns and behaviors. Although well-designed swarms can show advantages in adaptability, robustness, and scalability, it must be noted that SI system have not really found their way from lab demonstrations to real-world applications, so far. This is particularly true for embodied SI, where the agents are physical entities, such as in swarm robotics scenarios. In this paper, we start from these observations, outline different definitions and characterizations, and then discuss present challenges in the perspective of future use of swarm intelligence. These include application ideas, research topics, and new sources of inspiration from biology, physics, and human cognition. To motivate future applications of swarms, we make use of the notion of cyber-physical systems (CPS). CPSs are a way to encompass the large spectrum of technologies including robotics, internet of things (IoT), Systems on Chip (SoC), embedded systems, and so on. Thereby, we give concrete examples for visionary applications and their challenges representing the physical embodiment of swarm intelligence in autonomous driving and smart traffic, emergency response, environmental monitoring, electric energy grids, space missions, medical applications, and human networks. We do not aim to provide new solutions for the swarm intelligence or CPS community, but rather build a bridge between these two communities. This allows us to view the research problems of swarm intelligence from a broader perspective and motivate future research activities in modeling, design, validation/verification, and human-in-the-loop concepts