Unstable vector bundles on projective spaces

Speaker: Morgan Opie - UCLA Abstract: In this talk, I will talk about the subtleties of studying unstable complex vector bundles on complex projective spaces using stable homotopy theory. I’ll start with a classical example of techniques used by Atiyah-Rees to classify all complex rank $2$ topological vector bundles on $\mathbb{C}P^5$ using real K theory and discuss my work on complex rank $3$ topological vector bundles on $\mathbb{C}P^5$ using topological modular forms....

November 24, 2022

Global homotopy theory via lax limits

Speaker: Sil Linskens - University of Bonn Abstract: Global equivariant stable homotopy theory is a formalism which admits applications to orbifold cohomology, elliptic cohomology and importantly equivariant stable homotopy theory. Many important equivariant spectra admit global refinements, and these refinements have led to theoretical advances and have aided in calculations. However not only does global homotopy theory admit applications to equivariant homotopy theory, but it seems reasonable to expect that global homotopy theory is in some sense determined by equivariant homotopy theory....

November 10, 2022

Chromatic homotopy is multiplicatively algebraic at large primes

Speaker: Shaul Barkan - Hebrew University of Jerusalem Abstract: Stable homotopy theory is intimately related to the geometry of formal groups through the Adams Novkiov spectral sequence. Franke took a step towards making this analogy precise by introducing a derived category of certain sheaves on the moduli stack of formal groups as an analog of the $\infty$-category of spectra of chromatic height $\leq h$. He conjectured that at primes sufficiently larger than the height the homotopy truncation of the two categories coincide....

October 27, 2022

On Brauer Groups of Lubin-Tate Spectra

Speaker: Alicia Lima – University of Chicago Abstract: Brauer groups and Azumaya algebras play an important role in many areas of mathematics. For instance, Antieau and Gepner showed that the Brauer group of the sphere spectrum $\mathbb{S}$ is zero, giving us the rigidity result for $\mathbb{S}$-modules. In this talk, I will walk you through Hopkins and Lurie’s computation (up to a filtration) of the Brauer groups of Lubin-Tate spectra, which are important building blocks in Chromatic Homotopy Theory....

October 13, 2022

Localization theorem for the algebraic K-theory of stable infinity-categories

Speaker: Andrea Lachmann - University of Wuppertal Abstract: The Localisation Theorem is a classical result by Quillen, which for any localisation of rings yields a long exact sequence of K-groups. In this talk we will define the algebraic K-theory functor from stable $\infty$-categories to spaces or spectra, and produce an analogue of the localisation theorem for this setting. I have already given a short talk on this topic at the YTM, but this time I will go a lot more into detail, so you can still learn something new even if you attended my previous talk....

September 29, 2022

Dimensions of colimits

Speaker: Maxime Ramzi – Unversity of Copenhagen Abstract: We use the Hochschild-homological interpretation of dimensions and more generally traces in symmetric monoidal $\infty$-categories to produce formulas for dimensions and traces of colimits over sufficiently nice spaces. These formulas specialize on the one hand to the very classical character-theoretic formulas for dimensions of coinvariants in the case of vector spaces in characteristic $0$ and when the space is $BG$ for some finite group $G$; and on the other hand to the Blumberg-Cohen-Schlichtkrull formula for topological Hochschild homology of Thom spectra....

September 15, 2022

Polygons and TR with coefficients

Speaker: Jonas McCandless - University of Münster Abstract: I will introduce the notion of a polygonic spectrum which is a multi-object version of the notion of a cyclotomic spectrum indexed by polygons rather than the circle. This is designed to capture the structure on topological Hochschild homology of a ring with coefficients in a bimodule. Using this, I will explain the construction of TR with coefficients and explain how this is equipped with compatible Frobenius and Verschiebung maps....

September 1, 2022