# Seminarios

## Futuros Eventos

2020-02-29
12:00hrs.
Carolina Marchant. Facultad de Ciencias Básicas, Universidad Católica del Maule, Talca, Chile
Multivariate Birnbaum-Saunders Distributions: Modelling and Applications
Sala 5, Facultad de Matemáticas, Edificio Rolando Chuaqui, Campus San Joaquin, Pontificia Universidad Católica de Chile
Abstract:

Since its origins and numerous applications in material science, the Birnbaum-Saunders family of distributions has now found widespread uses in some areas of the applied sciences such as environment and medicine, as well as in quality control, among others. It is able to model varied data behaviour and hence provides a flexible alternative to the most usual distri- butions. The family includes Birnbaum–Saunders and log-Birnbaum–Saunders distributions in univariate and multivariate versions. There are now well-developed methods for estimation and diagnostics that allow in-depth analyses. This presentation gives a review of methods and of relevant literature, introducing properties and theoretical results in a systematic way. To emphasise the range of suitable applications, full analyses are included of examples based on regression and diagnostics in material science and control charts for environmental monitoring.

Seminario organizado por el Centro para el Descubrimiento de Estructuras en Datos Complejos - MiDaS.

http://midas.mat.uc.cl

2020-01-29
12:00 hrs.
Seminario Núcleo Milenio Midas
José Quinlan. Pontificia Universidad Católica de Chile
On the Support of Yao-based Random Ordered Partitions for Change-Point Analysis
Abstract:

In Bayesian change-point analysis for univariate time series, prior distributions on the set of ordered partitions play a key role for change-point detection. In this context, mixtures of product partition models based on Yao's cohesion are very popular due to their tractability and simplicity. However, how flexible are these prior processes to describe different beliefs about the number and locations of change-points? In this talk I will address the previous question in terms of its weak support.

Sala 1, Facultad de Matemáticas
2020-01-22
12:00 hrs.
Seminario Núcleo Milenio Midas
Miles Ott. Smith College
Respondent-Driven Sampling: Challenges and Opportunities
Abstract:
Respondent-driven sampling leverages social networks to sample hard-to-reach human populations, including among those who inject drugs, sexual minority, sex worker, and migrant populations.  As with other link-tracing sampling strategies, sampling involves recruiting a small convenience sample, who invite their contacts into the sample, and in turn invite their contacts until the desired sample size is reached. Typically, the sample is used to estimate prevalence, though multivariable analyses of data collected through respondent-driven sampling are becoming more common. Although respondent-driven sampling may allow for quickly attaining large and varied samples, its reliance on social network contacts, participant recruitment decisions, and self-report of ego-network size makes it subject to several concerns for statistical inference.  After introducing respondent-driven sampling I will discuss how these data are actually being collected and analyzed, and opportunities for statisticians to improve upon this widely-adopted method.
Sala 1, Facultad de Matemáticas
2020-01-22
15:45 hrs.
Seminario Fismat
Francesco Chiacchio. Universidad de Nápoles
Some isoperimetric problems in the Euclidean space with density
Abstract:
We will discuss the isoperimetric problem for factorized measures obtained as perturbations of the Gaussian and the anti-Gaussian, respectively. Among other things, we will show that some isoperimetric problems, for which balls centered at the origin are stable, have no solutions.Time permitting, some applications, like, for instance, Faber-Krahn type inequalities will be presented too. (Joint works with F. Brock and A. Mercaldo)
Sala 5, Facultad de Matemáticas
2020-01-21
16:00hrshrs.
Seminario de Análisis y Geometría
Barbara Brandolini. Departamento de Matemáticas, Universidad de Nápoles, Italia
Improved bounds for Hermite-Hadamard inequalities in higher dimensions
Abstract:
ver pdf
Sala 2, Facultad de Matemáticas
2020-01-15
12:00 hrs.
Seminario Núcleo Milenio Midas
Nicolas Kuschinski. Pontificia Universidad Católica de Chile
FATSO: Una familia de operadores para selección de variables en modelos lineales
Abstract:
En modelos lineales es común encontrarse con situaciones donde varios de los coeficientes de regresión son 0. En estas situaciones, una herramienta común es un operador de selección de variables de tipo "sparsity promoting". El más común de estos operadores es el LASSO, el cual promueve estimaciones en 0. Sin embargo, el LASSO y sus derivados dan poco en términos de parámetros fácilmente interpretables para controlar el grado de selectividad. En esta plática se propondrá una nueva familia de operadores de selección, la cual toma como base la geometría del LASSO, pero que tienen forma analítica distinta, y que dan una manera fácilmente interpretable de controlar el grado de selectividad. Estos operadores corresponden con densidades a priori propias, y por ende se pueden usar para hacer inferencia Bayesiana.
Sala 1, Facultad de Matemáticas
2020-01-14
14:30hrs.
Santiago Number Theory and Algebra Seminar (Santas)
Chao Li. Columbia University
On the Kudla-Rapoport conjecture
Abstract:
The classical Siegel-Weil formula relates certain Siegel Eisenstein series with quadratic forms, namely expressing special values of these series as theta functions --- generating series of representation numbers of quadratic forms. The influential program of Kudla aims to establish the arithmetic Siegel-Weil formula, which relates the derivative of certain Siegel Eisenstein series with generating series from arithmetic geometry. We will report a proof of the Kudla-Rapoport conjecture, and discuss its application to L-functions such as generalizations of the Gross-Zagier formula to higher dimension. This is joint work with Wei Zhang.
Sala de Seminarios, Dpto de Matemáticas. Las Palmeras 3425, Universidad de Chile
2020-01-10
14:00hrs.
Seminario de Teoría de Números
Chao Li. Columbia University
Elliptic curves and Goldfeld's conjecture
Abstract:

An elliptic curve is a plane curve defined by a cubic equation. Determining whether such an equation has infinitely many rational solutions has been a central problem in number theory for centuries, which lead to the celebrated conjecture of Birch and Swinnerton-Dyer. Within a family of elliptic curves (such as the Mordell curve family $y^2=x^3+d$), a conjecture of Goldfeld further predicts that there should be infinitely many rational solutions exactly half of the time. We will start with a history of this problem, discuss our joint work with D. Kriz towards Goldfeld's conjecture and illustrate the key ideas and ingredients behind these new progresses.

Sala 2
2020-01-08
14:00hrs.
Seminario de Geometría Algebraica
Luca Schaffler. University of Massachusetts At Amherst
Compactifications of moduli spaces of algebraic varieties
Abstract:
In algebraic geometry, an algebraic variety is a geometric object defined
by polynomial equations. The space of parameters for a family of algebraic
varieties may also be an algebraic variety called a moduli space. In this
talk oriented to a general audience, I will motivate the study of
compactifications of moduli spaces, focusing on the case of moduli of
polarized K3 surfaces. The original results (joint works with Moon and
Gallardo-Kerr) concern the study of a family of K3 surfaces arising from
eight points in the projective line, and the interplay between different
compactifications of such family coming from Geometric Invariant Theory,
Hodge Theory, and the Minimal Model Program.
sala 2