I will describe a famous conjecture, dating back from the 1980s, concerning the way that the electronic energy of an atom or a molecule depends on the number of electrons. Together with Simone Di Marino (Genova) and Mathieu Lewin (CNRS and Paris-Dauphine), we found the first counter-example by going to the semi-classical limit and studying an optimal transport problem. Our nuclei have a fractional charge and the conjecture remains open for integer charge systems, however.

Title: The Precedence-Constrained Family Traveling Salesman Problem

Speaker:  Raquel Bernardino, Department of Mathematics, Lisbon School of Economics and Management (ISEG)

Date | Time: April 8, 2026 | 14h30

Place: NOVA FCT,

Abstract:

We introduce the Precedence-Constrained Family Traveling Salesman Problem (PC- FTSP), which generalizes the FTSP by adding precedence relations between families. The PC-FTSP arises in warehouse order picking with scattered storage, where heavier items must be picked before lighter ones. We propose several formulations and compare them theoretically and empirically. We also derive valid inequalities that strengthen the linear programming (LP) relaxations. As some formulations are non- compact, we design a branch-and-cut algorithm to solve them. Results show the non- compact formulations outperform the compact ones, and the inequalities effectively strengthen the LP bounds on our instances.

Room 1.12 Building VII
   
Abstract: In this talk we will address the lifting problem for the Černý conjecture: namely, whether the validity of the conjecture for a quotient automaton can always be transferred (or “lifted”) to the original automaton. Although a complete solution remains open, we show that it is sufficient to verify the Černý conjecture for three specific subclasses of reset automata: radical, simple, and quasi-simple.  Our approach relies on establishing a Galois connection between the lattices of congruences and ideals of the transition monoid. This connection not only serves as the main tool in our proofs but also provides a systematic method for computing the radical ideal and for deriving structural insights about these classes.  
This is a joint work with Prof. Emanuele Rodaro.

Wave scattering is present in many applications regarding non destructive testing, namely medical imaging. In particular, in the context of inverse scattering problems, the goal is to find unknown properties of the obstacle (scatterer) from the knowledge of the incident field and the measurement of the scattered field or far-field pattern. In this talk, we will focus on numerical methods to solve mathematical models for time-harmonic scattering problems. We will focus on new approaches to ensure stability of the method of fundamental solutions to solve the direct problem and in numerical methods that deal with the ill-conditioning and nonlinearity of the inverse problem, in a time-harmonic wave propagation context. Finally, we will consider a numerical approach for a toy model for elastography, a medical imaging modality used for biological tissue imaging, focusing on their applications in the retina.

Room 1.12 ed. VII 
 
Abstract:  A minimal generating set of a group is a set of elements that generates the group such that, if any element is removed, the remaining set no longer generates the group. For example, the symmetric group of degree n has minimal generating sets whose sizes range from 2 up to n−1. The study of minimal generating sets is a topic of particular interest because of its connections with two important areas: discrete geometry and computational algebra. In discrete geometry, there is a well-known one-to-one correspondence between certain minimal generating sets of involutions satisfying specific axioms and regular polytopes. In computational algebra, the connectivity of product replacement graphs, an important tool used in algebra systems to generate random elements of groups, depends on the parameters m(G) and d(G), which denote the maximal and minimal sizes of minimal generating sets of a group G, respectively.

In this seminar, I will give an overview of the topic and discuss some of its main results and applications.