Analytical approximation of the exterior gravitational field of rotating neutron stars

It is known that B\"acklund transformations can be used to generate stationary axisymmetric solutions of Einstein's vacuum field equations with any number of constants. We will use this class of exact solutions to describe the exterior vacuum region of numerically calculated neutron stars. Therefore we study how an Ernst potential given on the rotation axis and containing an arbitrary number of constants can be used to determine the metric everywhere. Then we review two methods to determine those constants from a numerically calculated solution. Finally, we compare the metric and physical properties of our analytic solution with the numerical data and find excellent agreement even for a small number of parameters.Comment: 9 pages, 10 figures, 3 table

Open Problems on Central Simple Algebras

We provide a survey of past research and a list of open problems regarding central simple algebras and the Brauer group over a field, intended both for experts and for beginners.Comment: v2 has some small revisions to the text. Some items are re-numbered, compared to v

Apšvietimas kaip architektūros modernumo simbolis

The paper is designed to reveal the aesthetics of artificial lighting and its influence on the architecture of the 20th century. The main topics discussed are electric lighting, which appeard in our history at the end of the 19th century, and the technical development of lighting till the middle of the 20th century. Connections of artificial lighting with visual arts, its influence on advertisement, building architecture and the whole city are analysed. An idea is proposed that although lighting by nature was purely functional, very soon it acquired symbolic ambitions to represent architecture. In modern times architects understood that lighting was both a technological development and a symbol of a new era, when there appeared an independent field of creation - lighting architecture. Santrauka Straipsnyje nagrinėjama dirbtinio apšvietimo estetika ir jos įtaka XX a. architektūrai. Išryškinta XIX a. pabaigoje atsiradusio elektrinio apšvietimo svarba ir atskleista apšvietimo techninė raida iki XX a. vidurio. Nagrinėjamos dirbtinio apšvietimo sąsajos su vizualiaisiais menais, apšvietimo įtaka reklamai, pastatų architektūrai bei visam miestui. Straipsnyje keliama idėja, kad nors apšvietimo prigimtis pradžioje buvo grynai funkcionali, ji greitai įgavo simbolinių ambicijų – reprezentuoti architektūrą. Architektai į apšvietimą žvelgė ne tik kaip į technologinę pažangą, tai buvo naują erą ženklinantis simbolis, erą, kurioje atsiranda didelės įtakos visoms kūrybinėms idėjoms turinti nauja savarankiška kūrybos sritis – šviesos architektūra. First Published Online: 22 May 2013 Reikšminiai žodžiai: meninis, dirbtinis, elektrinis apšvietimas, stiklo, šviesos architektūra, modernumas

Record of forearc devolatilization in low-T, high-P/T metasedimentary suites: Significance for models of convergent margin chemical cycling

[1] The Franciscan Complex (Coast Ranges and Diablo Range, California) and the Western Baja Terrane (WBT; Baja California, Mexico) were metamorphosed along high-P/T paths like those experienced in many active subduction zones, recording peak conditions up to ∼1 GPa and 300°C. Franciscan and WBT metasedimentary rocks are similar in lithology and geochemistry to clastic sediments outboard of many subduction zones. These metamorphic suites provide evidence regarding devolatilization history experienced by subducting sediments, information that is needed to mass-balance the inputs of materials into subduction zones with their respective outputs. Analyzed samples have lower total volatile contents than their likely protoliths. Little variation in LOI among similar lithologies at differing metamorphic grades, suggests that loss of structurally bound water occurred during early clay-mineral transformations. Finely disseminated carbonate is present in the lowest-grade rocks, but absent in all higher-grade rocks. δ13CVPDB of reduced-C is uniform in the lower-grade Franciscan samples (mean = −25.1‰, 1σ = 0.4‰), but varies in higher-grade rocks (−28.8 to −21.9‰). This likely reflects a combination of devolatilization and C-isotope exchange, between organic and carbonate reservoirs. Nitrogen concentration ranges from 102 to 891 ppm, with δ15Nair of +0.1 to +3.0‰ (n = 35); this organic-like δ15N probably represents an efficient transfer of N from decaying organic matter to reacting clay minerals. The lowest-grade rocks in the Coastal Belt have elevated carbonate contents and correlated N-δ15N variations, and exhibit the most uniform δ13C and C/N, all consistent with these rocks having experienced less devolatilization. Most fluid-mobile trace elements are present at concentrations indistinguishable from protoliths. Suggesting that, despite apparent loss of much clay-bound H2O and CO2 from diagenetic cements (combined, <5–10 wt. %), most fluid-mobile trace elements are retained to depths of up to ∼40 km. Organic-like δ15N, lower than that of many seafloor sediments, is consistent with some loss of adsorbed N (perhaps as NO3−) during early stages of diagenesis. The efficient entrainment of fluid-mobile elements to depths of at least 40 km in these relatively cool subduction zone settings lends credence to models invoking transfer of these elements to the subarc mantle