Finite temperature dynamics of vortices in the two dimensional anisotropic Heisenberg model

We study the effects of finite temperature on the dynamics of non-planar vortices in the classical, two-dimensional anisotropic Heisenberg model with XY- or easy-plane symmetry. To this end, we analyze a generalized Landau-Lifshitz equation including additive white noise and Gilbert damping. Using a collective variable theory with no adjustable parameters we derive an equation of motion for the vortices with stochastic forces which are shown to represent white noise with an effective diffusion constant linearly dependent on temperature. We solve these stochastic equations of motion by means of a Green's function formalism and obtain the mean vortex trajectory and its variance. We find a non-standard time dependence for the variance of the components perpendicular to the driving force. We compare the analytical results with Langevin dynamics simulations and find a good agreement up to temperatures of the order of 25% of the Kosterlitz-Thouless transition temperature. Finally, we discuss the reasons why our approach is not appropriate for higher temperatures as well as the discreteness effects observed in the numerical simulations.

Mais além dos muros: o amor, a morte e os limites do humano em Rútilo nada, de Hilda Hilst

Esta dissertação procura analisar as configurações do humano e de seus limites no conto Rútilo nada, de Hilda Hilst. A questão das fronteiras do humano foi estudada a partir de uma análise da abordagem de Hilda Hilst aos temas da morte e do amor, bem como de uma interpretação das imagens de animalidade presentes no texto.

Majorana Zero Modes in Graphene

A clear demonstration of topological superconductivity (TS) and Majorana zero modes remains one of the major pending goals in the field of topological materials. One common strategy to generate TS is through the coupling of an s-wave superconductor to a helical half-metallic system. Numerous proposals for the latter have been put forward in the literature, most of them based on semiconductors or topological insulators with strong spin-orbit coupling. Here, we demonstrate an alternative approach for the creation of TS in graphene-superconductor junctions without the need for spin-orbit coupling. Our prediction stems from the helicity of graphene’s zero-Landau-level edge states in the presence of interactions and from the possibility, experimentally demonstrated, of tuning their magnetic properties with in-plane magnetic fields. We show how canted antiferromagnetic ordering in the graphene bulk close to neutrality induces TS along the junction and gives rise to isolated, topologically protected Majorana bound states at either end. We also discuss possible strategies to detect their presence in graphene Josephson junctions through Fraunhofer pattern anomalies and Andreev spectroscopy. The latter, in particular, exhibits strong unambiguous signatures of the presence of the Majorana states in the form of universal zero-bias anomalies. Remarkable progress has recently been reported in the fabrication of the proposed type of junctions, which offers a promising outlook for Majorana physics in graphene systems.

Dissertazione di Paolo Maria Paciaudi teatino : sopra una statuetta di Mercurio del gabinetto di S.E. il signor marchese dell'Ospital, ambasciatore di sua Maestà Cristianissima alla corte di Napoli.

Plates signed: Gaultier fec.

Boḥen Tsadiḳ, bo muva deʻot ʻal ha-sefer Megilah temirin ...

Photocopy. Chicago : University of Chicago Library, Photoduplication Dept., 1986.

Sochinenie Ravvina Y. Li͡andau ...

Works.

Avaḳ sofer : heʻarot ṿe-hagahot ṿe-ḥidushim le-Shulkhan ʻArukh Yoreh deʻah ṿe-Even ha-ʻezer = Abak Sofer /

Mode of access: Internet.

Secrets of the White Lady

Mode of access: Internet.