* Seuraavan viikon tapahtumat merkitty tähdellä
Kai Hippi (Aalto University)
Quantum mixing and Benjamini-Schramm convergence of hyperbolic surfaces
* Today * Tuesday 20 January 2026, 10:15, M3 (M234)
Quantum chaos studies how quantum systems reflect the chaotic behaviour of their classical counterparts. Two central notions in this field are quantum ergodicity and quantum mixing, which describe how quantum states spread out and how correlations between states behave in the high-energy limit.
Roughly speaking, a system is quantum ergodic if the expectation value of a fixed observable in most high-energy eigenfunctions approaches the classical average. Similarly, a system is quantum mixing if it is quantum ergodic and the associated transition amplitudes between states effectively decay in the high-energy limit. For compact hyperbolic surfaces a quantum ergodicity property was proven by Snirelman, Zelditch, and Colin de Verdière. Building on this, Zelditch proved that compact hyperbolic surfaces are quantum mixing.
In this talk, I will present a new large-scale analogue of Zelditch's quantum mixing theorem, which complements the large-scale quantum ergodicity theorem of Le Masson and Sahlsten. First, I will discuss the ideas leading to the new large-scale quantum mixing results and then I will present the main ideas of the proof. The talk is based on my recent work: https://arxiv.org/abs/2512.15504.
Hao Zhang (Tsinghua University)
Conformal Blocks and the Sewing-Factorization Theorem in Logarithmic CFT (remote talk over Zoom)
* Monday 26 January 2026, 09:00, Zoom
In this talk, I will present the SewingFactorization (SF) theorem for conformal blocks of an N-graded, C2-cofinite (not necessarily rational) vertex operator algebra (VOA). I will then discuss how the SF theorem relates to other approaches, including pseudo-trace methods in the VOA framework and the coend formalism in the topological field theory (TFT) approach. This talk is based on joint work with Bin Gui (arXiv:2503.23995, arXiv:2508.04532) and on my own work (arXiv:2509.07720).
Mathematical physics seminar
Vilma Moilanen (Aalto University)
Community detection in multivariate Hawkes processes using second-order statistics (MSc presentation)
* Monday 26 January 2026, 14:15, M3 (M234)
Hawkes processes are a class of mutually exciting temporal point processes where past events may increase the probability of future events. A multivariate Hawkes process consists of multiple interacting point processes, referred to as components. Each component has a conditional intensity that depends on the joint history of all components. Components can be partitioned into communities, defined as sets that share interaction parameters. The objective of the thesis is to develop a community detection method for stationary, symmetrically interacting Hawkes processes with light-tailed memory kernels. The latent community structure is shown to be encoded in the second-order cumulant of the process. The proposed method is based on applying spectral clustering to an estimator of the second-order cumulant. The main contribution of the thesis is a non-asymptotic, high-probability bound on the proportion of misclassified components. This result is obtained by developing a concentration inequality for the cumulant estimator as an extension of existing results for Hawkes process cumulants, and combining it with recovery guarantees for spectral clustering. The performance of the proposed method is illustrated on simulated data.
Aalto Stochastics & Statistics Seminar
Haihan Wu (Johns Hopkins University)
Webs and multiwebs for the symplectic group (remote talk over Zoom)
* Monday 26 January 2026, 16:00, Zoom
The dimer model is a statistical mechanical model that studies random dimer covers (perfect matchings) of a graph. Web categories are developed to compute the Witten-Reshetikhin-Turaev quantum invariants and to study the representations of quantum groups.
Kasteleyns theorem computes the number of dimer covers of a graph by calculating the determinant of a modified adjacency matrix. The generalizations of the theorem to higher dimer models involve type A web categories. I will talk about further generalizations to the type C cases, relaxing the bipartiteness condition of the underlying graph. This talk is based on joint work with Richard Kenyon.
Mathematical physics seminar
Joonas Vättö (Aalto University)
TBA
Tuesday 27 January 2026, 10:15, M3 (M234)
Prof. Andrea Pinamonti (Università di Trento)
TBA
Wednesday 04 February 2026, 10:15, M3 (M234)
Seminar on analysis and geometry
Nivedita (University of Oxford)
TBA
Tuesday 10 February 2026, 10:15, M3 (M234)
Prof. Anders Hansen (University of Cambridge)
TBA
Tuesday 10 February 2026, 15:15, M1 (M232)
Dr. Lucas Hataishi (University of Oxford)
TBA
Tuesday 17 February 2026, 10:15, M3 (M234)
Romain Usciati (Paris-Saclay)
TBA
Tuesday 24 February 2026, 10:15, M3 (M234)
Milla Laurikkala
Midterm review
Tuesday 24 February 2026, 11:15, M2 (M233)
Lorenzo Zacchini (Aalto University)
Fractional integrals on spaces of homogeneous type
Wednesday 25 February 2026, 10:15, M3 (M234)
Analysis seminar / Hytönen
Dr. John Urschel (MIT)
TBA
Tuesday 10 March 2026, 15:15, U5 (U147)
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