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Speaker: Professor Nathan Albin, Kansas State University
Title: Modulus, Duality, and Families of Objects on Graphs
Abstract:
Given a discrete graph and a family of objects (walks, spanning trees, edge covers, etc.) on the graph, p-modulus provides a mathematical way to quantify the "richness" or "robustness" of that family. Acting as a tunable metric, p-modulus generalizes classical graph metrics—such as shortest path, effective resistance, and minimum cut—to provide a multifaceted view of the graph's topology and geometry. Through the lens of modulus, we can explore a variety of structural properties of the graph. This talk will introduce p-modulus, describe its basic properties, connect it to well-known graph-theoretic quantities, and explore the powerful theory of Fulkerson blocking duality, which connects each family of objects to a natural dual family that provides deep insights into the graph's structural properties.
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Speaker: Dr. Sounak Kar, QuTech, TU Delft
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Title: Rocks instead of clocks: Bayesian modelling of the fossil record enlightens the diversification and extinction of Hemiptera in deep time
Abstract: Untangling the patterns and drivers behind the diversification and extinction of highly diversified lineages remains a challenge in evolutionary biology. While insect diversification has been widely studied through the “Big Four” insect orders (Coleoptera, Hymenoptera, Lepidoptera, and Diptera), the fifth most diverse order, Hemiptera, has often been overlooked. Hemiptera exhibit a rich fossil record and are highly diverse in present-day ecosystems, with many lineages closely associated with their host plants, making them a crucial group for studying how past ecological shifts—such as mass extinctions and floral turnovers—have influenced insect diversification. This study leverages birth-death models in a Bayesian framework and the fossil record of Hemiptera to estimate their past diversity dynamics. Our results reveal that global changes in flora over time significantly shaped the evolutionary trajectories of Hemiptera. Two major faunal turnovers particularly influenced Hemiptera diversification: (i) the aftermath of the Permo-Triassic mass extinction and (ii) the Angiosperm Terrestrial Revolution. Our analyses suggest that diversification of Hemiptera clades was driven by floristic shifts combined with competitive pressures from overlapping ecological niches. Leveraging the extensive fossil record of Hemiptera allowed us to refine our understanding of diversification patterns across major hemipteran lineages. We also the recently developed Bayesian Brownian Bridge model, which estimates the timing of lineage origin and extinction through fossil-based Bayesian modelling, to provide a temporal framework for the rise and fall of 310 major hemipteran lineages.
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Prof. Michael Lenhard, Institute for Biochemistry and Biology, University of Potsdam, Germany
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Guest seminar hosted by CDQT.
Speaker: Prof. Jeroen van den Brink (Institute for Theoretical Solid State Physics, IFW Dresden)
Title: Topological surface superconductivity in PtBi2
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Speaker: Dr. Kenan Qu, Department of Astrophysical Sciences, Princeton University
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Target audience: Interns, Students, PostDocs, and those who are interested in the same research field.
Language: English