Seminários, para a disseminação informal de resultados de investigação, trabalho exploratório de equipas de investigação, actividades de difusão, etc., constituem a forma mais simples de encontros num centro de investigação de matemática.
O CAMGSD regista e publica o calendário dos seus seminários há bastante tempo, servindo páginas como esta não só como um método de anúncio dessas actividades mas também como um registo histórico.
I will talk about recent joint work with Daniel Fadel (University of São Paulo) and Luiz Lara (Unicamp), where we study the SU(2) Yang-Mills-Higgs functional with positive coupling constant on 3-manifolds. Motivated by the work of Alessandro Pigati and Daniel Stern (2021) on the U(1)-version of the functional, we also include a scaling parameter.
When the 3-manifold is closed and the parameter is small enough, by adapting to our context the min-max method used by Pigati and Stern, we construct non-trivial critical points satisfying energy upper and lower bounds that are natural from the point of view of scaling.
Then, over 3-manifolds with bounded geometry, we show that, in the limit as the parameter tends to zero, and under the above-mentioned energy upper bound, a sequence of critical points exhibits concentration phenomenon at a finite collection of points, while the remaining energy goes into an $L^2$ harmonic 1-form. Moreover, the concentrated energy at each point is accounted for by finitely many "bubbles", that is, non-trivial critical points on $R^3$ with the scaling parameter set to 1.
We consider the characterization of global attractors $A_f$ for semiflows generated by scalar one-dimensional semilinear parabolic equations of the form $u_t = u_{xx} + f(u,u_x)$, defined on the circle $x\in S^1$, for a class of reversible nonlinearities. We modify a proof developed for nonlinearities of simple type, making it simpler and amenable to generalization. We obtain a classification up to connection equivalence of global attractors for $S^1$-equivariant parabolic equations.
We prove that the space of symplectic embeddings of $n\geq 1$ standard balls, each of capacity at most $\frac{1}{n}$, into the standard complex projective plane $\mathbb{CP}^2$ is homotopy equivalent to the configuration space of $n$ points in $\mathbb{CP}^2$. Our techniques also suggest that for every $n \geq 9$, there may exist infinitely many homotopy types of spaces of symplectic ball embeddings.
In this talk I will review the notion of unbalanced optimal transport, introduced $\sim10$ years ago to handle mass variarions betwenn nonnegative measures. I will discuss the induced pseudo-Riemannian structure and gradient-flow evolution, corresponding to some class of parabolic reaction-diffusion equations. If time permits I will present two applications: a fitness-driven model from population dynamics, and a Hele-Shaw free boundary problem for tumor growth.
