Rigidity and flexibility of surface groups

The aim of this work is the °exibility of the hyperbolic surfaces. The results are about °exibility and geometrical boundedness. Bers are stated the universal property for all hyperbolic surface of ¯nite area where introduced the constant of boundedness. We determine this constant, using symbolic dynamics

The first eigenvalue of the Laplacian and the Conductance of a Compact surface

We present some results with the central theme of is the phenomenon of the first eigenvalue of the Laplacian and conductance of the dynamical system. Our main tool is a method for studying how the hyperbolic metric on a Riemann surface behaves under deformation of the surface. With this model, we show variation of the first eigenvalue of the laplacian and the conductance of the dynamical system, with the Fenchel–Nielsen coordinates, that characterize the surface

Geodesic length spectrum on compact Riemann surfaces

In this paper we use techniques linking combinatorial structures (symbolic dynamics) and algebraic-geometric structures to study the variation of the geodesic length spectrum, with the Fenchel-Nielsen coordinates, which parametrize the surface of genus τ = 2. We explicitly compute length spectra, for all closed orientable hyperbolic genus two surfaces, identifying the exponential growth rate and the first terms of growth series

Free radially expanding liquid sheet in air: time- and space-resolved measurement of the thickness field

The collision of a liquid drop against a small target results in the formation of a thin liquid sheet that extends radially until it reaches a maximum diameter. The subsequent retraction is due to the air-liquid surface tension. We have used a time- and space-resolved technique to measure the thickness field of this class of liquid sheet, based on the grey level measurement of the image of a dyed liquid sheet recorded using a fast camera. This method enables a precise measurement of the thickness in the range $(10-450) \, \mathrm{\mu m}$, with a temporal resolution equal to that of the camera. We have measured the evolution with time since impact, $t$, and radial position, $r$, of the thickness, $h(r,t)$, for various drop volumes and impact velocities. Two asymptotic regimes for the expansion of the sheet are evidenced. The scalings of the thickness with $t$ and $r$ measured in the two regimes are those that were predicted in \citet{Rozhkov2004} fort the short-time regime and \citet{Villermaux2011} for the long time regime, but never experimentally measured before. Interestingly, our experimental data also evidence the existence of a maximum of the film thickness $h_{\rm{max}}(r)$ at a radial position $r_{\rm{h_{max}}}(t)$ corresponding to the crossover of these two asymptotic regimes. The maximum moves with a constant velocity of the order of the drop impact velocity, as expected theoretically. Thanks to our visualization technique, we also evidence an azimuthal thickness modulation of the liquid sheets.Comment: accepted for publication in Journal of Fluid Mechanic

The first eigenvalue of the Laplacian and the ground flow of a compact surface

We present some results whose central theme is that the phenomenon of the first eigenvalue of the Laplacian and the ground flow of the compact surface (bitorus). Our main tool is a method for studying how the hyperbolic metric on a Riemann surface behaves under deformation of the surface. With this model, we show that there are variation of the first eigenvalue of the Laplacian and the ground flow with the Fenchel-Nielsen coordinates, that characterize the surface

Open-charm mesons in nuclear matter at finite temperature beyond the zero-range approximation

The properties of open charm mesons, D, D, D{sub s}, and D{sub s} in nuclear matter at finite temperature are studied within a self-consistent coupled-channel approach. The interaction of the low-lying pseudoscalar mesons with the ground-state baryons in the charm sector is derived from a t-channel vector-exchange model. The in-medium scattering amplitudes are obtained by solving the Lippmann-Schwinger equation at finite temperature including Pauli blocking effects, baryon dressing, as well as D, D, D{sub s}, and D{sub s} self-energies taking their mutual influence into account. We find that the in-medium properties of the D meson are affected by the D{sub s}-meson self-energy through the intermediate D{sub s}Y loops coupled to DN states. Similarly, dressing the D meson in the DY loops has an influence over the properties of the D{sub s} meson

Buzzle : (play with the) architectures of the world

Buzzle – (Play with the) Architectures of the world (at home), é um trabalho de investigação desenvolvido no âmbito do Mestrado em Gestão Cultural, realizado na Escola Superior de Artes e Design das Caldas da Rainha. Este conduziu à criação de um objecto: um puzzle tridimensional dedicado ao património arquitectónico, nomeadamente o considerado icónico e excepcional. A investigação aborda a estreita relação entre o significado cultural da arquitectura e a sua importância tanto para o campo do turismo como para o do conhecimento. O projecto procura aliar o saber e a experiência específicos da arquitectura à concepção de um jogo de construção. Ao ambicionar-se a valorização do património construído através do entretenimento educativo, o resultado final é um Conceito lúdico. Para chegar a um produto cultural original, realizou-se um estudo de múltiplos factores determinantes para o sucesso do Projecto, nomeadamente estratégias para a sua produção/manufacturação/produção em massa e consequentemente eventual implantação no mercado enquanto Marca. Identificam-se alternativas em termos de produção, estudo de materiais e técnicas de produção, bem como a tecnologia e equipamentos específicos necessários à sua produção, processo que implicou contactos com investigadores, profissionais e empresas do domínio da impressão 3D. Todo o estudo encaminhou-se em dada altura para a produção de um protótipo, realizado com o apoio da Escola Superior de Artes e Design das Caldas da Rainha; uma vez concretizada a peça – uma micro-arquitectura em forma de jogo de encaixes – passa a poder ser possível aperfeiçoar, no futuro, não apenas pormenores construtivos em função de diferentes contextos, como também aspectos do desempenho da obra enquanto objecto convidando à participação e ao conhecimento. Considera-se que o presente trabalho atinge um patamar de concreção conceptual e problemática que abre vias para um conceito cultural de excelência, que, no entanto, passa a estar disponível, desde já, de acordo com diversos modos de abordar as indústrias culturais. Em síntese, a abrangência etária e cultural do Buzzle é assaz vasta e a sua aplicação lúdico-pedagógica não menos. É compromisso da sua autora lutar pela sua disseminação, em tempo próprio e recorrendo aos parceiros adequados. Em todo o caso, uma das possibilidades de concretização deste jogo – talvez a mais aliciante – é aliás a sua propagação através da Internet em rede aberta, funcionando como um serviço de Open Design e não necessariamente, pelo menos a curto prazo, como um produto final. Esta opção posiciona o Buzzle como produto decisivo para o estabelecimento de parcerias com diversas entidades, instituições e empresas, nomeadamente espaços museológicos, estabelecimentos de ensino. O Buzzle abre amplo espaço de manobra à Gestão Cultural para fazer a diferença, no que diz respeito a uma sempre necessária mediação entre a produção cultural lato senso e a sua disseminação como acontecimento participado. Buzzle, nestes termos, permite que joquemos à arquitectura, mas em casa

Trend tests: a tendency to resampling

Trend analysis is an important problem in time series. Many studies have been developed to investigate this issue, with special attention to its application to environmental and hydrological time series. The presence of autocorrelation and missing observations affects the significance and power of trend tests, parametric or non-parametric. This study assesses the performance of two trend tests, t-test and the Mann-Kendall through an appropriate resampling technique. A new procedure based onsubsampling is proposed in order to assure good statistical properties of these tests. A comparison was established between this new approach and others already developed, such as bootstrap-based tests. In order to evaluate the performance of the new method, a simulation study is conducted considering a set of underlying slopes, different values of autocorrelation and different fractions of randomly missing data. The order of autocorrelation structure is estimated by the best fitting model obtained through the Akaike information criterion. Inspection of the data to detect missing observations is required, before applying the trend tests. In case of missing observations, their estimation and replace is performed by an imputation method available in software.info:eu-repo/semantics/publishedVersio

Chaotic behavior in an economic model

The purpose of this work is to study a discrete-time nonlinear business cycle model of the Kaldor-type. The model is an extended Kaldor model and it is described by a two-dimensional dynamical system with income and capital as variables. We check the orbits of the system, their changes related to changes of the system parameters and their basins of attraction in order to understand the dynamic features of the model

Markets, financial institutions and central banks in the face of climate change: challenges and opportunities

El cambio climático y la transición a una economía baja en carbono implican al sistema financiero mediante dos vías. Primero, por su papel de canalizador de la financiación necesaria para realizar las cuantiosas inversiones que requiere el cumplimiento del Acuerdo de París. En los últimos años se han producido avances —aún insuficientes— en el desarrollo de nuevos productos, siendo los bonos verdes el instrumento de financiación verde más avanzado. Segundo, por los riesgos financieros que el cambio climático y la transición hacia una economía de bajo carbono implican, los cuales afectan al balance de las entidades financieras y tienen, además, una naturaleza sistémica. Esto significa que las instituciones financieras han de evaluar estos riesgos y su exposición a ambos, aunque no es una tarea fácil. Todavía hay obstáculos y retos que superar, como la falta de una taxonomía completa que comprenda lo que es «verde» y lo que no lo es, la falta de información y de conocimiento de las metodologías apropiadas, y el largo e incierto horizonte temporal de estos riesgos, que exige el desarrollo de nuevas competencias y la integración de estos riesgos en el conjunto de la organización, así como la adopción de un enfoque prospectivo. Por último, las responsabilidades de los bancos centrales en materia de supervisión bancaria, estabilidad financiera, gestión de activos y política monetaria también hacen necesario analizar las posibles implicaciones sistémicas que pueden tener para la economía y el sistema financiero en su conjunto, con el fin de incorporar las cuestiones relativas al cambio climático en sus prácticas de supervisión y macroprudenciales, en la gestión de sus propias carteras y, dentro de sus mandatos, en su marco de política monetaria. Los avances realizados en los últimos años por los mercados financieros, las instituciones financieras y los bancos centrales han sido significativos, aunque todavía queda camino por recorrer.Climate change and the transition to a low-carbon economy involve the financial system in two ways. First, because it channels the funds needed to make the large investments to comply with the Paris Agreement. Recent years have seen headway, albeit insufficient, in the development of new products, of which green bonds are the most advanced green financing instrument. Second, because of the financial risks associated with climate change and the transition to a low-carbon economy, which affect financial institutions’ balance sheets and are, moreover, systemic. This means that financial institutions have to assess these risks and their exposure to both of them, although it is not an easy task. There are still obstacles and challenges to overcome, such as the lack of a complete taxonomy that comprises what is “green” and what is not green, the lack of information on and knowledge of appropriate methodologies, and the long and uncertain time horizon of these risks, which calls for rolling out new skills and integrating these risks in the whole of the organisation, as well as taking a forward-looking approach. Lastly, central banks’ responsibilities regarding bank supervision, financial stability, asset management and monetary policy also make it necessary for them to analyse the potential systemic implications they may have for the economy and the financial system as a whole in order to incorporate climate-change issues into their supervisory and macro-prudential practices, into the portfolio management of their own portfolios, and, within their mandates, in their monetary policy framework. The progress made in recent years by financial markets, financial institutions and central banks has been significant although there is still a way to go