Ordering in Heisenberg Spin Glasses

For five different Heisenberg spin glass systems, torque experiments were performed in applied magnetic fields up to $4 T$. The Dzyaloshinski-Moriya random anisotropy strengths, the in-field torque onset temperatures, and the torque relaxation were measured. Critical exponents were estimated independently using a standard protocol. The data are strong evidence for a true spin glass ordered state which survives under high applied magnetic fields; they can be interpreted consistently in terms of a chiral ordering model with replica symmetry breaking as proposed by Kawamura and coworkers.Comment: 4 pages 4 figures. Revised version accepted by PR

Fast and Compact Distributed Verification and Self-Stabilization of a DFS Tree

We present algorithms for distributed verification and silent-stabilization of a DFS(Depth First Search) spanning tree of a connected network. Computing and maintaining such a DFS tree is an important task, e.g., for constructing efficient routing schemes. Our algorithm improves upon previous work in various ways. Comparable previous work has space and time complexities of $O(n\log \Delta)$ bits per node and $O(nD)$ respectively, where $\Delta$ is the highest degree of a node, $n$ is the number of nodes and $D$ is the diameter of the network. In contrast, our algorithm has a space complexity of $O(\log n)$ bits per node, which is optimal for silent-stabilizing spanning trees and runs in $O(n)$ time. In addition, our solution is modular since it utilizes the distributed verification algorithm as an independent subtask of the overall solution. It is possible to use the verification algorithm as a stand alone task or as a subtask in another algorithm. To demonstrate the simplicity of constructing efficient DFS algorithms using the modular approach, We also present a (non-sielnt) self-stabilizing DFS token circulation algorithm for general networks based on our silent-stabilizing DFS tree. The complexities of this token circulation algorithm are comparable to the known ones

Carbon-rich planet formation in a solar composition disk

The C--to--O ratio is a crucial determinant of the chemical properties of planets. The recent observation of WASP 12b, a giant planet with a C/O value larger than that estimated for its host star, poses a conundrum for understanding the origin of this elemental ratio in any given planetary system. In this paper, we propose a mechanism for enhancing the value of C/O in the disk through the transport and distribution of volatiles. We construct a model that computes the abundances of major C and O bearing volatiles under the influence of gas drag, sublimation, vapor diffusion, condensation and coagulation in a multi--iceline 1+1D protoplanetary disk. We find a gradual depletion in water and carbon monoxide vapors inside the water's iceline with carbon monoxide depleting slower than water. This effect increases the gaseous C/O and decreases the C/H ratio in this region to values similar to those found in WASP 12b's day side atmosphere. Giant planets whose envelopes were accreted inside the water's iceline should then display C/O values larger than those of their parent stars, making them members of the class of so-called ``carbon-rich planets''.Comment: 8 pages, 4 figures, accepted for publication Ap

The measured compositions of Uranus and Neptune from their formation on the CO iceline

The formation mechanisms of the ice giants Uranus and Neptune, and the origin of their elemental and isotopic compositions, have long been debated. The density of solids in the outer protosolar nebula is too low to explain their formation, and spectroscopic observations show that both planets are highly enriched in carbon, very poor in nitrogen, and the ices from which they originally formed might had deuterium-to-hydrogen ratios lower than the predicted cometary value, unexplained properties observed in no other planets. Here we show that all these properties can be explained naturally if Uranus and Neptune both formed at the carbon monoxide iceline. Due to the diffusive redistribution of vapors, this outer region of the protosolar nebula intrinsically has enough surface density to form both planets from carbon-rich solids but nitrogen-depleted gas, in abundances consistent with their observed values. Water rich interiors originating mostly from transformed CO ices reconcile the D/H value of Uranus and Neptune's building blocks with the cometary value. Finally, Our scenario generalizes a well known hypothesis that Jupiter formed on an iceline (water snowline) for the two ice giants, and might be a first step towards generalizing this mechanism for other giant planets.Comment: The Astrophysical Journal (in press), 8 pages, 5 figure

L'arquitectura eclèctica a Catalunya: una història per escriure

Con este artículo nos proponemos rescatar un legado arquitectónico ignorado e incomprendido: la arquitectura ecléctica catalana. A través de un repaso de las obras más importantes del eclecticismo en Cataluña, pretendemos organizar una primera clasificación, definiendo las diferentes tendencias así como introduciendo un intento de cronología. También se destacan aspectos como la relación entre el eclecticismo y los nuevos materiales del siglo XIX, mostrando que no es un estilo tan "anacrónico" como se ha pretendido, así como la asimilación de las influencias europeas, principalmente francesa y germánica, en la obra de nuestros arquitectos. Finalmente pretendemos hacer hincapié en que junto a la deslumbrante arquitectura modernista, el atracti

Ciutat industrial versus ciutat burguesa: el cas de l'"Eixample" berlinès, 1815-1896

Este artículo analiza el proceso de planificación y realización del Bebauungsplan o «ensanchen berlinés, entre 181 5 y 1896. Esta actuación difiere en gran parte de la mayoría de los grandes planes urbanísticos de la época, aplicados a capitales europeas como Londres, París o Viena, dado que fue pensado en función de la fuerte implantación de grandes complejos industriales y ferroviarios, sin tener en cuenta la creación de espacios representativos del nuevo poder burgués, como había sucedido en las otras ciudades. Así en los proyectos diseñados sucesivamente por Joseph Schmidt, Josef Lenn6 y James Hobrecht, se dará prioridad a la ubicación de canales, fábricas, almacenes, viviendas humildes, en detrimento de les grandes avenidas perspectivísticas, de las plazas dedicadas a edificios públicos, de los jardines ornamentales y de la vivienda burguesa que se concentrará, hasta principios del siglo XX, en el centro histórico de la ciudad, construido bajo la monarquía absolutista en el siglo XVIII. Además, vemos como la propia dinámica constructiva de la ciudad, que fue siempre por delante de la planificación, obliga a los urbanistas a plantear y replantear sus proyectos una y otra vez.This article analyzes the process of planning and execution of the Bebauungsplan or Berliner city expansion between 181 5 and 1896. This process differed from the majority of great city-planning projects of that period applied to European capitals such as London, Paris and Vienna, in that it was based on the large-scale introduction of big industrial and  railroad buildings, without taking into consideration the design of spaces representativeof new middle-class power, as had happened in other cities. Thus, in the projects that were successively designed by Joseph Schmidt, Josef Lenné and James Hobrecht, priority was given to the location of canals, factories, warehouses and housing for the working classes rather than to long wide avenues, town squares dedicated to public buildings, ornamental gardens and the middle-class housing, which became concentrated, until the beginning of the 20th Century, in the historic city centre, built under the absolutist monarchy in the 18th Century. Besides, we will see how the constructive force of the city itself, rather than planning, forced the city-planning experts to restate their projects time and again