10/01/2020
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SIMBa: Learning the structure of graphical models by covariance queries

Actualització 14/1/20: Atenció, canvi d’aula! La xerrada se celebrarà a l’aula S1

El proper dimecres, 15 de gener, se celebrarà una nova xerrada del Seminari Informal de Matemàtiques de Barcelona (SIMBa).

Speaker: Vasiliki Velona
Universitat: Universitat Politècnica de Catalunya.

Data: Wednesday, 15th of January
Hora: 12:00,coffee break (be eco friendly, bring your cup); 12:20, talk.
Lloc: ~~B1 classroom~~, Facultat de Matemàtiques de la Universitat de Barcelona.
Idioma: English

Títol: Learning the structure of graphical models by covariance queries
Resum: I will talk about the problem of learning the zero-pattern of theinverse covariance matrix of a Gaussian distribution, in the high-dimensional setting. This is a problem with several applications,for instance inference of genetic networks. After giving a con-crete mathematical statement of the problem, I will discuss someefficient algorithms as well as lower bounds for their performance.

Si voleu estar al cas de les xerrades previstes, podeu consultar el calendari. Si voleu proposar una xerrada, ompliu el formulari. Si voleu contactar amb els responsables podeu escriure un missatge a seminari(dot)simba(at)ub(dot)edu.

29/11/2019
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SIMBa: The philosophy of the $h$-principle

El proper dimecres, 4 de desembre, se celebrarà una nova xerrada del Seminari Informal de Matemàtiques de Barcelona (SIMBa).

Speaker: Robert Cardona Aguilar
Universitat: Universitat Politècnica de Catalunya

Data: Wednesday, 4th of December
Hora: 12:00, coffee break; 12:20, talk
Lloc: B1 classroom, Facultat de Matemàtiques de la Universitat de Barcelona.
Idioma: English

Títol: The philosophy of the $h$ -principle
Resum: The homotopy principle (or $h$ -principle) is a very general way tosolve partial differential equations and relations which frames ide-as of Smale and Nash. It is a far-reaching tool with applicationsin a lot of different topics as PDE’s, foliations, cobordisms, sym-plectic topology or Riemannian geometry. Gromov’s work was arevolution in geometry even if th $h$ -principle has been known as “the hardest part of Gromov’s work to popularize”. In this talk,we will present a very informal approach to these ideas and com-ment some of its applications. Time permiting, we will mentionshortly how it is used in a recent paper in the context of contacttopology, and prove a conjecture concerning the Euler equationsfor ideal fluids in Riemannian manifolds. This last part is a jointwork with E. Miranda, D. Peralta-Salas and F. Presas.

25/11/2019
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SIMBa: Postquantum cryptography: what, why, and how?

El proper dimecres, 27 de novembre, se celebrarà una nova xerrada del Seminari Informal de Matemàtiques de Barcelona (SIMBa).

Speaker: Enric Florit Zacarías
Universitat: Universitat de Barcelona

Data: Wednesday, 27th of November
Hora: 12:00, coffee break; 12:20, talk
Lloc: Aula B1 Facultat de Matemàtiques de la Universitat de Barcelona.
Idioma: English

Títol: Postquantum cryptography: what, why, and how?
Resum: The key agreement scheme proposed by Diffie and Hellman in 1976 relies on the problem of finding discrete logarithms. One can choose appropriate groups where the best algorithms for solving this problem are too slow, such as certain elliptic curves over finite fields. There are already proposed quantum algorithms that break discrete logarithms in polynomial time. For this reason multiple “post-quantum” cryptography primitives have appeared in the last years, while trying to find harder computational problems. One of the proposed protocols using elliptic curves is SIDH/SIKE, candidate to the NIST Post-Quantum Cryptography Competition.

10/06/2019
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SIMBa: Isogenies and Cryptography

El proper dimecres, 12 de juny, se celebrarà una nova xerrada del Seminari Informal de Matemàtiques de Barcelona (SIMBa).

Speaker: Coral Real Llamas
Universitat: Eurecat – Centre Tecnològic de Catalunya

Data: Dimecres, 12 de juny de 2019
Hora: 12:00, cafè; 12:20, xerrada
Lloc: Aula B1 Facultat de Matemàtiques de la Universitat de Barcelona.
Idioma: Castellà

Títol: Isogenies and Cryptography
Resum: Nowadays in post-quantum cryptography the use of isogenies isincreasing. They are used in key exchange or in signature sc-hemes. After a brief introduction to the concept of isogeny, inthis talk we explain how they are being used in quantum-resistantcryptography.

03/06/2019
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SIMBa: On an efficient implementation of the Roe scheme for large hyper-bolic systems

El proper dimecres, 5 de juny, se celebrarà una nova xerrada del Seminari Informal de Matemàtiques de Barcelona (SIMBa).

Speaker: Ernesto Pimentel García
Universitat: Universidad de Málaga

Data: Dimecres, 5 de juny de 2019
Hora: 12:00, cafè; 12:20, xerrada
Lloc: Aula B1 Facultat de Matemàtiques de la Universitat de Barcelona.
Idioma: Anglès

Títol: On an efficient implementation of the Roe scheme for large hyper-bolic systems
Resum: There exist several schemes to solve numerically hyperbolic sys-tems of Partial Differencial Equations. Two of them are the Sim-ple Riemann solvers (SRS) and the Polynomial Viscosity matrix(PVM) methods.
The results obtained by Morales de Luna et al. (2014) concerningthe relation between SRS and the PVM methods are revisited andapplied to the efficient implementation of the Roe method for largehyperbolic systems either conservative or non-conservative. Thisimplementation, based on the Newton’s form of the interpolationpolynomial, will be applied to the two-layer shallow water modeland a non-conservative model for rarefied gas flow.

17/05/2019
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SIMBa: On a theorem of Waring for plane algebraic curves

El proper dimecres, 22 de maig, se celebrarà una nova xerrada del Seminari Informal de Matemàtiques de Barcelona (SIMBa).

Speaker: Andrés Rojas González
Universitat: Universitat de Barcelona

Data: Dimecres, 22 de maig de 2019
Hora: 12:00, cafè; 12:20, xerrada
Lloc: Aula B1 Facultat de Matemàtiques de la Universitat de Barcelona.
Idioma: Anglès

Títol: On a theorem of Waring for plane algebraic curves
Resum: Waring’s theorem is a classic result about the intersection of plane algebraic curves. Roughly speaking, it asserts that the barycenter of the intersection points is determined by the asymptotes of the curves.
After a short historical introduction, in this talk we present the ideas that allow to obtain an extension of Waring’s theorem. Finally, we see some consequences; the most important of them will be a theorem due to Chasles.

06/05/2019
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SIMBa: Algebraic versus semi-algebraic conditions for phylogenetic varieties

El proper dimecres, 8 de maig, se celebrarà una nova xerrada del Seminari Informal de Matemàtiques de Barcelona (SIMBa).

Speaker: Marina Garrote López
Universitat: Universitat Politècnica de Catalunya

Data: Dimecres, 8 de maig de 2019
Hora: 12:00, cafè; 12:20, xerrada
Lloc: Aula B1 Facultat de Matemàtiques de la Universitat de Barcelona.
Idioma: Anglès

Títol: Algebraic versus semi-algebraic conditions for phylogenetic varieties
Resum: It is well known that there exists a close relationship between Phylogenetics and Algebraic Geometry. It is common to modelevolution adopting a parametric statistical model which allowsto define a joint probability distribution at the leaves of the trees. When these models are algebraic, one is able to deduce polynomial relationships between these probabilities, and the study of these polynomials and the geometry of the algebraic varieties that arisefrom them can be used to reconstruct phylogenetic trees. However not every point in this algebraic varieties has biological sense. In this talk we would like to discuss the importance of studying the subset of these varieties with biological sense and explore the extent to which restricting to these subsets can provide insight into existent methods of phylogenetic reconstruction.