La primavera de l’edat moderna? L’economia catalana i la suposada «crisi baixmedieval» (1350-1450)

Passejant pel nucli antic de Barcelona i observant els meravellosos edificis gòtics encara existents, a un historiador se li fa difícil d’acceptar que aquella època esplendorosa en l’àmbit arquitectònic fou una època de crisi econòmica. Un plantejament totalment contraintuïtiu, però que ha perdurat fins als nostres temps fonamentalment per l’autoritat dels seus dos màxims defensors: Pierre Vilar i Jaume Vicens Vive

Data analysis and navigation in high-dimensional chemical and biological spaces

The goal of this master thesis is to develop and validate a visual data-mining approach suitable for the screening of chemicals in the context of REACH [Registration, Evaluation, Authorization and Restriction of Chemicals]. The proposed approach will facilitate the development and validation of non-testing methods via the exploration of environmental endpoints and their relationship with the chemical structure and physicochemical properties of chemicals. The use of an interactive chemical space data exploration tool using 3D visualization and navigation will enrich the information available with additional variables like size, texture and color of the objects of the scene (compounds). The features that distinguish this approach and make it unique are (i) the integration of multiple data sources allowing the recovery in real time of complementary information of the studied compounds, (ii) the integration of several algorithms for the data analysis (dimensional reduction, generation of composite variables and clustering) and (iii) direct user interaction with the data through the virtual navigation mechanism. All this is achieved without the need for specialized hardware or the use of specific devices and high-cost virtual reality and mixed reality

Ultraviolet line-driven disc winds as a feedback mechanism in bright active galactic nuclei

Astronomical observations have shown that galaxies and the supermassive black holes (BH) located at their centres have evolved together over cosmic time. BH grow by accreting matter from their surroundings and the gravitational potential energy released by the infalling matter can power the enormous luminosities we see in active galaxies and quasars, and is in principle sufficient to significantly disrupt the structure of the host galaxy. However, the particular physical processes through which such active galactic nuclei feedback affects the host galaxy are still poorly understood. One possibility is that the accretion process powers winds that travel through the galactic bulge, displacing the gas reservoir and thus quenching star formation in the galaxy. There are various mechanisms that could drive such winds. In this thesis, we focus on the study of UV line-driven winds originating from the surface of accretion discs, which are driven by radiation pressure on spectral lines and are also present in hot stars. We develop a numerical simulation method for the study of such systems, building up on existing models and incorporating modern computational techniques to study the conditions under which these winds can be launched and accelerated. The resulting model, called Qwind, features relativistic corrections to the radiation flux, as well as an algorithm to perform ray tracing on axisymmetric geometries. We also develop a model to compute the initial conditions to launch the wind from the surface of the accretion disc, based on theoretical frameworks employed in the study of O-star winds. Using this new model, we are able to investigate the dependence of the wind properties on the BH mass, mass accretion rate, and the innermost launching radius of the wind, thus deriving the amount of momentum and energy carried by the wind for different AGN systems

The Lee-Yang Theorem and applications

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Any: 2015, Tutor: Tomeu FiolWe present the Lee-Yang theory that links the study of phase transitions to the localization of zeros in the complex fugacity plane. We prove the Lee-Yang theorem using Asano's contraction method and we apply it for the one and two dimensional Ising model. We also show that the Lee-Yang formalism can shed some light on the di cult task of counting the number of ground states in supersymmetric theories