Noticias en español
Distance evolutions in growing preferential attachment graphs.
Abstract: In this talk we will study the evolution of the graph distance between two fixed vertices in dynamically growing random graph models. More precisely, we consider preferential attachment models with parameters such that the asymptotic degree distribution has infinite second moment. First, we grow the graph until it contains $t$ vertices, then we sample $u_t, v_t$ uniformly at random from the largest component and study the evolution of the graph distance as the surrounding graph grows. This yields a stochastic process in $t’\ge t$ that we call the distance evolution. We...
Read MoreAnálisis de Clusters para velocidades GNSS que revelan patrones de deformación del ciclo sísmico y de la estructura andina.
Resumen: A partir de técnicas de aprendizaje automático no supervisado se analizan los desplazamientos de la corteza a escala continental en áreas afectadas por el ciclo sísmico de grandes terremotos de subducción a lo largo de Chile. Particularmente, usamos algoritmos de clustering como una herramienta exploratoria para la investigación de patrones espaciales en velocidades GNSS regionales, sin incurrir en las complejidades de modelar una fuente física. Como datos utilizados, presentamos un campo de velocidad a escala continental que incluye todos los datos GNSS disponibles, para dos...
Read MoreExperimentation in Two-Sided Marketplaces: The Impact of Interference.
Abstract: Marketplace platforms use experiments (also known as “A/B tests”) as a method for making data-driven decisions about which changes to make on the platform. When platforms consider introducing a new feature, they often first run an experiment to test the feature on a subset of users and then use this data to decide whether to launch the feature platform-wide. However, it is well documented that estimates of the treatment effect arising from these experiments may be biased due to the presence of interference driven by the substitution effects on the demand and supply sides of the...
Read MoreA limit law for the most favorite point of a simple random walk on a regular tree.
We consider a continuous-time random walk on a regular tree of finite depth and study its favorite points among the leaf vertices. We prove that, for the walk started from a leaf vertex and stopped upon hitting the root, as the depth of the tree tends to infinity the maximal time spent at any leaf converges, under suitable scaling and centering, to a randomly-shifted Gumbel law. The random shift is characterized using a derivative-martingale-like object associated with the square-root local-time process on the tree.
Read MoreExistence of solutions on the critical hyperbola for a pure Lane-Emden system with Neumann boundary conditions.
Abstract: I will present some recent results obtained in collaboration with A. Pistoia and H. Tavares for a Lane-Emden system on a bounded regular domain with Neumann boundary conditions and critical nonlinearities. We show that, under suitable conditions on the exponents in the nonlinearities, least-energy (sign-changing) solutions exist. In the proof we exploit a dual variational formulation which allows to deal with the strong indefinite character of the problem, and we establish a compactness condition which is based on a new Cherrier type inequality. We then prove such condition by...
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