Anàlisi

Inner factors of Dirichlet space functions
Michael Hartz (Saarland University)
Dia: 05/03/2026
Hora: 15:00
Lloc: CRM, Auditori (C1/034)

Resum: Every function in the Dirichlet space on the unit disc has an inner/outer factorization. Which inner functions occur in this way? For Blaschke products, this is the old question of which subsets of the disc are zero sets for the Dirichlet space.
I will talk about general inner factors of Dirichlet space functions. Moreover, I will indicate how results about singular inner factors lead to new sufficient conditions for zero sets. This is joint work with Stefan Richter.

Structure of one-dimensional metric currents
Emanuele Caputo (University of Warwick)
Dia: 03/03/2026
Hora: 16:00
Lloc: CRM, Auditori (C1/034)

Resum: The goal of the talk is to give an overview of the metric theory of currents by Ambrosio-Kirchheim, together with some recent progress. Metric currents are a generalization to the metric setting of classical currents. Classical currents are the natural generalization of oriented submanifolds, as distributions play the same role for functions. We present a structure result for metric 1-currents as superposition of 1-rectifiable sets in complete and separable metric spaces, which generalizes a previous result by Schioppa. This is based on an approximation result of metric 1-currents with normal 1-currents and a more refined analysis in the Banach space setting. This is joint work with D. Bate, J. Takáč, P. Valentine, and P. Wald (Warwick).

Geometria

Symplectic Tiling Billiards on Complete Affine Tori
Charles Daly (MPI Leipzig)
Dia: 13/03/2026
Hora: 12:30
Lloc: Dpt Matematiques, Seminari C3B (C3B/158)

Web: Departament de Matemàtiques de la UAB

Resum: Symplectic tiling billiards is a game played on a tiling of the plane that only relies on a notion of parallelism and lends itself to study under the more general non-Euclidean affine structures of the torus. In this talk we will address the classification of affine structures on the torus and how to use them to play symplectic tiling billiards. Demonstrations of the game will be provided in real time along with arguments to explain observed behavior of orbits. This is joint with with Fabian Lander.

Models Estocàstics i Deterministes

Convergence in law for quasi-linear SPDEs
Lluís Quer-Sardanyons (UAB)
Dia: 12/03/2026
Hora: 15:00
Lloc: Dpt Matematiques, Seminari C3B (C3B/158)

Resum: We consider the quasi-linear stochastic wave and heat equations in $\mathbb{R}^d$ with $d\in \{1,2,3\}$ and $d\geq 1$, respectively, and perturbed by an additive Gaussian noise which is white in time and has a homogeneous spatial correlation with spectral measure $\mu_n$. We allow the Fourier transform of $\mu_n$ to be a genuine distribution. Let $u^n$ be the mild solution to these equations. We provide sufficient conditions on the measures $\mu_n$ and the initial data to ensure that $u^n$ converges in law, in the space of continuous functions, to the solution of our equations driven by a noise with spectral measure $\mu$, where $\mu_n\to\mu$ in some sense. We apply our main result to various types of noises, such as the anisotropic fractional noise. We also show that we cover existing results in the literature, such as the case of Riesz kernels and the fractional noise with $d=1$.

Teoria d'Anells

KMS states on separated graph C*-algebras I
Joan Claramunt (UPC)
Dia: 02/03/2026
Hora: 11:30
Lloc: Dpt Matematiques, Seminari C3B (C3B/158)

Web: Laboratori d'Interaccions entre Geometria, Àlgebra i Topologia

Resum: The study of KMS states on finite graph C*-algebras was initiated in 2013 by Kajiwara and Watatani, and simultaneously by an Huef, Laca, Raeburn and Sims. While the former focused on graphs with sinks and sources, the latter initially concentrated on strongly connected graphs. Subsequently, in 2014 and 2015, an Huef et al. fully characterized the simplex of KMS states for arbitrary finite graphs, including the reducible case.

In this talk, we present an ongoing project, joint with P. Ara (UAB), E. Gillaspy (UM) and F. Lledó (UC3M) concerning the existence and structure of KMS states on finite separated graph C*-algebras. In contrast to standard graph C*-algebras, the separated structure introduces a combinatorial complexity that significantly restricts the existence of KMS states. Nevertheless, I will present a method for constructing such states based on amalgamated probability.

Together with a second method to be discussed in subsequent talks, we demonstrate that there exist infinitely many KMS states which restrict to the same probability measure on the vertices of the graph. This stands in sharp contrast to the case of finite graphs, where a KMS state is uniquely determined by its values on the vertices.