Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

The Kardar-Parisi-Zhang (KPZ) class is a paradigmatic example of universality in nonequilibrium phenomena, but clear experimental evidences of asymptotic 2D-KPZ statistics are still very rare, and far less understanding stems from its short-time behavior. We tackle such issues by analyzing surface fluctuations of CdTe films deposited on polymeric substrates, based on a huge spatio-temporal surface sampling acquired through atomic force microscopy. A \textit{pseudo}-steady state (where average surface roughness and spatial correlations stay constant in time) is observed at initial times, persisting up to deposition of $\sim 10^{4}$ monolayers. This state results from a fine balance between roughening and smoothening, as supported by a phenomenological growth model. KPZ statistics arises at long times, thoroughly verified by universal exponents, spatial covariance and several distributions. Recent theoretical generalizations of the Family-Vicsek scaling and the emergence of log-normal distributions during interface growth are experimentally confirmed. These results confirm that high vacuum vapor deposition of CdTe constitutes a genuine 2D-KPZ system, and expand our knowledge about possible substrate-induced short-time behaviors.Comment: 13 pages, 8 figures, 2 table

The modulated spin liquid: a new paradigm for URu2_2Si2_2

We argue that near a Kondo breakdown critical point, a spin liquid with spatial modulations can form. Unlike its uniform counterpart, we find that this occurs via a second order phase transition. The amount of entropy quenched when ordering is of the same magnitude as for an antiferromagnet. Moreover, the two states are competitive, and at low temperatures are separated by a first order phase transition. The modulated spin liquid we find breaks $Z_4$ symmetry, as recently seen in the hidden order phase of URu$_2$Si$_2$. Based on this, we suggest that the modulated spin liquid is a viable candidate for this unique phase of matter.Comment: 4 pages, 2 figure

Dynamics of Enceladus and Dione inside the 2:1 Mean-Motion Resonance under Tidal Dissipation

In a previous work (Callegari and Yokoyama 2007, Celest. Mech. Dyn. Astr. vol. 98), the main features of the motion of the pair Enceladus-Dione were analyzed in the frozen regime, i.e., without considering the tidal evolution. Here, the results of a great deal of numerical simulations of a pair of satellites similar to Enceladus and Dione crossing the 2:1 mean-motion resonance are shown. The resonance crossing is modeled with a linear tidal theory, considering a two-degrees-of-freedom model written in the framework of the general three-body planar problem. The main regimes of motion of the system during the passage through resonance are studied in detail. We discuss our results comparing them with classical scenarios of tidal evolution of the system. We show new scenarios of evolution of the Enceladus-Dione system through resonance not shown in previous approaches of the problem.Comment: 36 pages, 12 figures. Accepted in Celestial Mechanics and Dynamical Astronom

Unevenly-sampled signals: a general formalism of the Lomb-Scargle periodogram

The periodogram is a popular tool that tests whether a signal consists only of noise or if it also includes other components. The main issue of this method is to define a critical detection threshold that allows identification of a component other than noise, when a peak in the periodogram exceeds it. In the case of signals sampled on a regular time grid, determination of such a threshold is relatively simple. When the sampling is uneven, however, things are more complicated. The most popular solution in this case is to use the "Lomb-Scargle" periodogram, but this method can be used only when the noise is the realization of a zero-mean, white (i.e. flat-spectrum) random process. In this paper, we present a general formalism based on matrix algebra, which permits analysis of the statistical properties of a periodogram independently of the characteristics of noise (e.g. colored and/or non-stationary), as well as the characteristics of sampling.Comment: 10 pages, 11 figures, Astronomy and Astrophysics, in pres

Geração de cenários de mudança de uso do solo na Amazônia Legal brasileira em função do agronegócio e da aplicação de políticas públicas.

As mudanças climáticas podem afetar a biodiversidade, da mesma forma, a contínua perda da biodiversidade pode, por sua vez, afetar a regulação do clima apresentando graves consequências para o desenvolvimento sustentável e o bem-estar humano. As mudanças no uso da terra, o desmatamento e as mudanças climáticas impactam fortemente o ecossistema da floresta amazônica ameaçando sua resiliência e a sustentabilidade de muitas atividades humanas. Este trabalho descreve a utilização da modelagem dinâmica para gerar cenários de mudança de uso da terra da Amazônia Legal Brasileira, buscando elaborar cenários de mudança de uso/cobertura em função do Agronegócio (agricultura, pastagem e reflorestamento) e considerando o desflorestamento legal, ocasionado pela exploração econômica do território. Os cenários de referência foram baseados nos cenários de desenvolvimento SSP1P, SSP5S e SSP5P do IPCC adapatados a situação de cada estado da Amazônia Legal e considerando-se as políticas brasileiras de desenvolvimento durável, tais como implantação do Plano ABC (Agricultura de Baixo Carbono), código florestal, dentre outras. Este trabalho, ainda em desenvolvimento, é parte do projeto ROBIN ? Role of Biodiversity in Climate Cahnge Mitigation ? financiado pela Comissão Europeia (FP7 ENV. 2011.2.1.4 -1: potencial de biodiversidade e ecossistemas para a mitigação das alterações climáticas), cujo objetivo geral é melhorar a compreensão sobre as relações da biodiversidade com o processo de mitigação de mudança climática