Centre for Mathematics, University of Coimbra

Seminars - Historic

Algebra and Combinatorics

A tour in extreme value laws

2018-03-09

Speaker: Jorge Soares (UC|UP PhD student)

In this talk, we analyse the stochastic process that arises from a dynamical system by evaluating an observable function along a given orbit of the system. Our goal is to give sufficient conditions for the existence of an Extreme Value Law for the considered process. We will present an...

Product formulas, generalized convolutions and integral transforms

2018-03-09

Speaker: Rúben Sousa (UC|UP PhD student)

It is well-known that the ordinary convolution is closely related with the Fourier transform. It is therefore natural to ask: for other important integral transforms, can we define generalized convolution operators having analogous properties? Actually, the answer depends on the existence of...

Phaseless rank and amoebas

2018-03-09

Speaker: António Goucha (UC|UP PhD student)

The phaseless rank of a nonnegative matrix M is defined to be the least k for which there exists a complex matrix N such that |N| = M, entrywise speaking. In optimization terms, it is the solution to the rank minimization of a matrix under phase uncertainty on the entries. This concept has a...

Integers and ideals: there and back again

2017-10-18

Speaker: Peter Lombaers (UC|UP PhD student)

In number theory, when you try to solve an equation in a number field, it is often more convenient to work with ideals than with integers. This stems from the fact that ideals have unique factorization, but integers may not. I will explain the advantages and difficulties of this method...

Introducing (T,V) -categories

2017-10-18

Speaker: Willian Silva (UC|UP PhD student)

In this seminar we introduce the concept of (T,V)-categories through its fundamental examples. In order to do so, we explore the concepts of monads and quantales, also with examples. We finish relating to the work on cartesian closed categories. The seminar takes place in...

SOS versus SDSOS polynomial optimization

2017-10-18

Speaker: Mina Saee Bostanabad (UC|UP PhD student)

It is NP-hard to decide whether a polynomial is nonnegative, however, semidefinite programming can be used to decide whether a polynomial is a sum of squares of polynomials (SOS) in a practically efficient manner. In the context of polynomial optimization, it has become usual to substitute...

Two mathematical approaches in ophthalmology

2017-06-01

Speaker: Maryam Khaksar Ghalati

TBA Maryam Khaksar Ghalati is a former PhD student of the Joint PhD Program UC|UP, in the area "Numerical Analysis andOptimization" under the supervision of professors Adérito Araújo and Sílvia Barbeiro. ...

Reducibility of nilpotent cone for G-Higgs bundle moduli space

2017-06-01

Speaker: Azizeh Nozad (Univ. Lisboa)

TBA Azizeh Nozad is a Postdoctoral fellow at Faculty of Science, University of Lisbon....

Statistical instability for the contracting Lorenz flow

2017-06-01

Speaker: Muhammad Ali Khan (UP student)

TBA Muhammad Ali Khan is a PhD student of the Joint PhD Program UC|UP, working at the University of Porto, in the areaof "Dynamical Systems" under the supervision of professor José Ferreira Alves. ...

Homotopy Excision

2016-06-28

Speaker: Fernando Lucatelli Nunes (UC student)

Eilenberg and Steenrod proved that ordinary homology is characterized by five axioms. Later, Atiyah, Hirzebruch and Whitehead observed that there are other families of functors that satisfy the four "most important" axioms. They defined the so called "generalized homology...

Homological Algebra

2016-06-28

Speaker: Artur de Araujo (UP student)

We will explain the basic concepts of Homological Algebra (Cech cohomology, injective/projective resolutions, derived functors,) and show why, useful as they are, they have shortcomings for a general theory of cohomology. Time allowing, we'll give a hint of why derived categories make up for...

Topological spaces as algebras

2016-05-19

Speaker: Pier Giorgio Basile (UC PhD student)

Monads, or triples, and the algebras they define, proved to be very important in several fields of mathematics. For example, they allow us to see the algebraic nature owned by topological spaces. This fact, for what concerns compact Hausdorff spaces, is known since 1969 (see [4]). By...

On topological semi-abelian algebras

2016-04-07

Speaker: Mathieu Duckerts-Antoine (CMUC)

In this talk, we will study some aspects of the categories of topological semi-abelian algebras. In particular, I will explain why these categories are homological. If the time allows it, I will also explain what is a torsion theory in a homological category and give several examples in the...

The k-word problem over DRG

2016-03-10

Speaker: Célia Borlido (UPorto student)

The study of finite semigroups has its roots in Theoretical Computer Science. In particular, in the mid nineteen seventies, Eilenberg [2] established the link between "varieties of rational languages", which is an important object of study in Computer Science, and certain classes...

Besov and Triebel-Lizorkin spaces with variable exponents

2016-02-18

Speaker: Helena Gonçalves (Technische Univ. Chemnitz, Germany)

See the attached file. Helena Gonçalves is working as a Research Assistant at Chemnitz University of Technology, Germany in the area of "Analysis" under the supervision of Prof. Henning Kempka.The seminar takes place in PORTO. ...

The spectral inclusion regions of linear pencils and numerical range

2016-01-28

Speaker: Fatemeh Esmaeili Taheri (CMUC)

Let A,B be n×n (complex) matrices. We are mainly interested in the study of the structure of the spectrum of a linear pencil, that is, a pencil of the form A−λB, where λ is a complex number. Our main purpose is to obtain spectral inclusion regions for the pencil...

An overview on the dimension of projected patterns in reaction-diffusion systems

2015-12-17

Speaker: Juliane Fonseca de Oliveira (UPorto student)

TBA...

Tuning polymeric and drug properties in a drug-eluting stent: a numerical study

2015-12-17

Speaker: Jahed Naghipoor (ISM, Bauhaus-Universität Weimar, Germany)

TBA...

The electrostatic limit for the Zakharov system

2015-11-19

Speaker: Luigi Forcella (Scuola Normale Superiore di Pisa, Italy)

The Zakharov system describes the coupled dynamics of the electric field amplitude and the low frequency fluctuation of the ions in a unmagnetized or weakly magnetized plasma. This system couples Schrödinger-like and wave equations and in its physical derivation depends on a parameter...

Analogies between optimal transport and minimal entropy

2015-11-19

Speaker: Luigia Ripani (Univ. Claude Bernard Lyon 1, France)

The Schrödinger problem is an entropic minimization problem and it's a regular approximation of the Monge-Kantorovich problem, at the core of the Optimal Transport theory.In this talk I will first introduce the two problems, then I will describe some analogy between optimal transport...

On pseudovarieties of forest algebras

2015-10-27

Speaker: Saeid Alirezazadeh

Forest algebras are used in the theory of formal languages. They consist of two monoids, the horizontal one H and the vertical one V , with an action of V on H, and a complementary axiom of faithfulness. The main example is the forest algebras of plane forests and contexts, that is to say...

Rolling maps and applications

2015-10-22

Speaker: Fátima Pina

Rolling motions are rigid motions subject to holonomic and nonholonomic constraints. These motions appear associated to certain engineering areas, such as robotics and computer vision. Rolling maps are the mathematical tools to describe rolling motions.In this talk, the concept of rolling...

Birationality of moduli spaces of twisted U(p,q)-Higgs bundles

2015-09-29

Speaker: Azizeh Nozad (Univ. Porto)

Let X be a Riemann surface of genus g greater or equal than 2. A twisted U(p,q)-Higgs bundle consists of a pair of holomorphic vector bundles on a Riemann surface, together with a pair of twisted maps between them. Here we study the variation with the parameter of the moduli space of...

Numerical solution of time-dependent Maxwell's equations in anisotropic materials for modelling light scattering in human eye's structure

2015-09-24

Speaker: Maryam Khaksar Ghalati

Modelling light propagation in biological tissue has become an important research topic in biomedical optics with application in diverse fields as for example in ophthalmology. Waveguides with induced anisotropy may worth to be modeled as they could play a role in biological waveguides. For...

\(3\times 3\) matrices with a flat portion on the boundary of the numerical range

2013-05-29

Speaker: Fatemeh Esmaeili Taheri (CMUC PhD student)

In recent years, many studies have been done on the numerical range of matrices and bounded operators. In this presentation, the set of unitarily irreducible complex 3×3 matrices whose numerical range has a flat portion will be explicitly described and it will show that this set is connected...

On trace spaces of 2-microlocal Triebel-Lizorkin spaces with variable integrability

2013-05-29

Speaker: Helena Gonçalves (PhD student)

In this seminar we study the traces of 2-microlocal Triebel-Lizorkin spaces with variable integrability on hyperplanes. Following [2], we present the definition and properties of those spaces, in particular the characterization by atomic decomposition and embedding assertions, needed to...

Categories of lax algebras: a first approach

2013-05-22

Speaker: Pier Giorgio Basile (PhD student)

Following the paper of M.M. Clementino and D. Hofmann [2], and having as starting point Barr's description of topological spaces as lax algebras for the ultrafilter monad [1], I am going to present the categories of lax algebras. They represent a suitable generalization of the relational...

Structures on line bundles - The deRham and Dolbeault grupoids

2013-05-15

Speaker: Artur Araújo (PhD student)

Brief introduction to connections and complex structures on a trivial line bundles. Deformation theories; the action of gauge transformations, and the deRham grupoid. Holomorphic structures on a line bundle, and relation to connections. Higgs fields, and the Dolbeault grupoid. Equivalence of...

Every prespectrum represents a homology theory

2013-05-15

Speaker: Fernando Lucatelli (PhD student)

On Besov and Triebel-Lizorkin-type spaces

2013-04-11

Speaker: Susana Moura (CMUC/Univ. Coimbra)

We give a survey on Besov and Triebel-Lizorkin spaces, from classical to 2-microlocal spaces with variable integrability. Embeddings and traces will be considered....

Experiments with numerical semigroups

2013-04-03

Speaker: Manuel Delgado (CMUP/Univ. Porto)

A set of natural numbers that is closed under addition and whose complement in the set of non negative integers is finite is said to be a numerical semigroup. The number of positive integers not belonging to a numerical semigroup is said to be its genus. Question: How many numerical...

An introduction to Sasakian geometry

2013-03-20

Speaker: Antonio De Nicola (CMUC)

I will introduce the first elements of contact and almost contact geometry, starting from the notion of contact manifold. I will briefly mention its relation with symplectic geometry as well as some application to physics. Finally, I will present the notions of normality and compatible...

Stability of heteroclinic networks

2013-03-19

Speaker: Sofia Castro (Fac. Economia, Univ. Porto)

Invariant sets are important objects in the study of dynamical systems since they allow us to describe families of trajectories/solutions. In fact, a solution starting in an invariant set will remain in this set for all time. Whether this solution is complex...

Fickian diffusion versus non Fickian diffusion in porous media

2013-03-13

Speaker: José Augusto Ferreira (CMUC/Univ. Coimbra)

Traditionally, diffusion process in porous media are described by convection-diffusion-reaction equations established using Fick's law for the mass flux. Such equations give accurate results in laboratory environment for perfectly homogeneous media. Nevertheless when nonhomogeneous media...

Dirac structures

2013-02-27

Speaker: Raquel Caseiro (CMUC/Univ. Coimbra)

Dirac structures were introduced by T.Courant and A. Weinstein as a way to unify pre-symplectic and Poisson geometry. We intend to present the basics of Dirac structures, including main geometric features and key examples. First we introduce linear Dirac structures and then we generalize...

A short introduction to Coxeter systems through combinatorics of words

2013-02-20

Speaker: Alessandro Conflitti (CMUC/Univ.Coimbra)

We give an introduction to abstract Coxeter systems using a combinatorial approach based on words, thus avoiding all the original geometric framework. The talk will be self contained, assuming no previous knowledge or background, save for very basic algebra....