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Monday, 25 May 2026
Time Speaker Title Resources
09:30 to 11:00 Samik Basu (ISI Kolkata, India) Thom spectra and multiplicative structures
  • The stable homotopy category
  • Ring spectra 
  • Thom spectra as ring spectra 
  • The examples of M^-TM and LM^-™
     
11:30 to 13:00 Vigleik Angeltveit (ANU, Canberra, Australia) Quick introduction to Chromatic homotopy theory

We will introduce Formal Group Laws, the Complex Cobordism spectrum MU and its p-typical version BP. We will also mention the Smith-Toda complexes V(n), Morava K-theory and Morava E-theory. We will also briefly discuss what we mean by localization.

14:30 to 15:30 Samik Basu (ISI Kolkata, India) Spanier Whitehead duality
  • Spanier Whitehead duals of manifolds embedded in R^n 
  • Atiyah duality 
  • Orientations and Thom spectra 
  • HF_p as a Thom spectrum
     
16:00 to 17:00 Nathalie Wahl (University of Copenhagen, København, Denmark) Hochschild Homology and String Topology (Lecture 1) (Online)
  • Universal operations on the Hochschild complex of algebras over a prop
  • String topology operations via the Hochschild complex
  • Algebraic structures on Tate-Hochschild complex
     
Tuesday, 26 May 2026
Time Speaker Title Resources
09:30 to 11:00 Samik Basu (ISI Kolkata, India) Thom spectra and their THH
  • Generalized Thom spectra 
  • Topological Hochschild Homology 
  • A formula for THH of Thom spectra
     
11:30 to 13:00 Gabriel Angelini-Knoll (Case Western Reserve University, USA) Introduction to topological Hochschild homology
  • Topological Hochschild homology 
  • The circle action
  • Power operations
  • THH(F_p) and THH(Z_p;F_p) 
     
14:30 to 15:30 Vigleik Angeltveit (ANU, Canberra, Australia) The original definition of TC, with a focus on setup from equivariant homotopy theory

We will discuss the difference between categorical fixed points and geometric fixed points of a group G acting on a spectrum X, and how this gives rise to the isotropy separation sequence. We will discuss the various structure maps connecting THH(R)^{C_n} for different n, the connection with Witt vectors, and how this gives a definition of TC(R). We will also need the homotopy orbit, homotopy fixed point, and Tate spectrum, and the corresponding spectral sequences for computing the homotopy groups of these.

16:00 to 17:00 Nathalie Wahl (University of Copenhagen, København, Denmark) Hochschild Homology and String Topology (Lecture 2) (Online)
  • Universal operations on the Hochschild complex of algebras over a prop
  • String topology operations via the Hochschild complex
  • Algebraic structures on Tate-Hochschild complex
     
Thursday, 28 May 2026
Time Speaker Title Resources
09:30 to 11:00 Gabriel Angelini-Knoll (Case Western Reserve University, USA) Cyclotomic spectra and topological cyclic homology
  • Cyclotomic spectra 
  • Topological Hochschild homology as a cyclotomic spectrum 
  • TC^{-}, TP, TC
     
11:30 to 13:00 Samik Basu (ISI Kolkata, India) Computations for HF_p and for LM
  • THH of  F_p via Thom spectra 
  • Topological Hochschild cohomology 
  • The topological Hochschild cohomology of M^-TM
     
16:00 to 17:00 Adela YiYu Zhang (University of Copenhagen, København, Denmark) Extensions of open 2D TFT’s (Lecture 1) (Online)

We will recall the construction of (T)HH via factorization homology, and introduce the ∞-category of nD bordisms with boundary. The ∞-subcategory O of open 2D bordisms corepresents E_1-Frobenius algebras.

Friday, 29 May 2026
Time Speaker Title Resources
09:30 to 11:00 Gabriel Angelini-Knoll (Case Western Reserve University, USA) The even filtration
  • t-structures
  • The even filtration on commutative ring spectra
  • Computing the even filtration
  • The even filtration and complex motivic homotopy theory
     
11:30 to 13:00 Vigleik Angeltveit (ANU, Canberra, Australia) Computations of TC of finite fields, the p-adic integers, and the Adams summand of complex K-theory

We will go through the calculations of TC and K of F_p, and more generally perfect fields, in detail to show “height -1 to height 0”. Then do the same for TC and K of the p-adic integers, and more generally p-typical Witt vectors, to show “height 0 to height 1”. Briefly sketch how the same kind of calculation works for the Adams summand of complex K-theory.

14:30 to 15:30 Samik Basu (ISI Kolkata, India) TBA
16:00 to 17:00 Adela YiYu Zhang (University of Copenhagen, København, Denmark) Extensions of open 2D TFT’s (Lecture 2) (Online)

We show that the ∞-category OC of open-closed 2D-bordisms is the initial symmetric monoidal extension of O admitting (T)HH. As a corollary, OC parametrizes the space of universal operations on E_1-Frobenius algebras.

Monday, 01 June 2026
Time Speaker Title Resources
09:30 to 11:00 Vigleik Angeltveit (ANU, Canberra, Australia) Computations of TC of pointed monoid rings, including truncated polynomial rings

Pointed monoid rings include examples like truncated polynomial rings and group rings. THH of a pointed monoid ring splits as the smash product of THH of the ring and the cyclic bar construction on the pointed monoid, and we will explain how this allows us to do computations.

11:30 to 13:00 Christian Ausoni (University of Paris, France) Algebraic K-theory and the trace maps
  • The Algebraic K-theory of rings and ring spectra;
  • The Bökstedt trace and the cyclotomic trace maps;
  • The Dundas-Goodwillie-McCarthy Theorem and its applications.
     
14:30 to 15:30 Katherine Poirier (CUNY, New York, USA) String Topology and Moduli Space Operations (Lecture 1)
  • Chas–Sullivan loop product (chain/homology level)
  • Cohen–Godin operations via fatgraphs
  • Moduli space operations
  • Compactifications and higher structures
     
16:00 to 17:00 Gabriel Angelini-Knoll (Case Western Reserve University, USA) Syntomic cohomology and prismatic cohomology
  • quasisyntomic rings and ring spectra
  • Motivic filtrations on THH, TC^{-}, TP, and TC
  • Syntomic cohomology and prismatic cohomology of truncated Brown--Peterson spectra
     
Tuesday, 02 June 2026
Time Speaker Title Resources
09:30 to 11:00 Ayelet Lindenstrauss (Indiana University, Bloomington, USA) Cyclic Sets and Circle Actions

Cyclic sets are a special case of simplicial sets with a crossed simplicial group action. I will discuss those and why they come with an action of the geometric realization of the crossed simplicial group, show what this looks like in the case of cyclic structure, and relate that to the cyclotomic structure on THH that was discussed in Vigleik Angeltveit's and Christian Ausoni's talks.

11:30 to 13:00 Katherine Poirier (CUNY, New York, USA) String Topology and Moduli Space Operations (Lecture 2)
  • Chas–Sullivan loop product (chain/homology level)
  • Cohen–Godin operations via fatgraphs
  • Moduli space operations
  • Compactifications and higher structures
     
14:30 to 15:30 Christian Ausoni (University of Paris, France) The chromatic redshift Conjectures
  •     Review of the first examples of redshift;
  •     Chromatic localizations;
  •     The statement of the conjectures;
  •     Proven cases.
     
16:00 to 17:00 Abhinandan Das (ISI Kolkata, India) Equivariant Twisted \(R\)-algebras via Thom Spectra

For a \(C_2\)-commutative ring spectrum \(R\), a twisted \(R\)-algebra is an \(R\)-module equipped with a multiplication whose order is switched by the \(C_2\)-action; equivalently, such objects are algebras over the little \(\sigma\)-disks operad. In this talk, we present a construction of quotients of \(C_2\)-commutative ring spectra as twisted algebras using equivariant Thom spectra, under suitable cofree and evenness assumptions.

As a motivating example, we consider \(KR/2\) as a twisted \(KR\)-algebra and compute its real topological Hochschild homology over \(KR\). This involves a computation of the splitting of the spectrum of units \(gl_1(KR)\), together with an identification of the real topological Hochschild homology of such Thom spectra as Thom spectra themselves.

This talk is based on joint work with Samik Basu.

Wednesday, 03 June 2026
Time Speaker Title Resources
09:30 to 11:00 Christian Ausoni (University of Paris, France) Localization and logarithmic variants
  • Localization sequences in algebraic K-theory;
  • Logarithmic THH and TC;
  • Examples of root adjunctions.
     
11:30 to 13:00 Ayelet Lindenstrauss (Indiana University, Bloomington, USA) Loday Constructions

Hochschild homology is a Loday construction on the standard model of the circle. I will define Loday constructions and discuss Loday constructions on other spaces, specifically spheres (and their stabilization) and higher tori.

14:30 to 15:30 Safdar Quddus (SWAL, Chennai, India) On the Hochschild and Cyclic Homology of Certain Noncommutative Spaces

We study the Hochschild and cyclic (co)homology of certain low-dimensional noncommutative spaces and orbifolds. Special attention is given to the Chern--Connes pairing and its relation to the topology of the underlying noncommutative spaces. We further discuss how Hochschild homology captures geometric and topological information, illustrating the interplay between homological invariants and noncommutative geometry.

16:00 to 17:00 Mukilraj K (IISER Kolkata, India) Integral Cyclic Homology of Products of Odd Spheres

By Jones's theorem, the negative cyclic homology $\HC^-_\ast(C^\ast(Y))$ of a simply connected space $Y$ computes the $S^1$-equivariant cohomology of its free loop space $LY$. Rationally, the right-hand side is computable via Sullivan minimal models (Burghelea--Vigu\'e-Poirrier), but integrally HKR fails for exterior algebras over $\Z$ and explicit cyclic torsion enters.

I describe an integral computation of $\HC^-_\ast(\Lambda_\Z(e_1, \ldots, e_r))$, equivalently the integral $S^1$-equivariant cohomology of $LX$ for $X = \prod_i S^{2k_i - 1}$ a finite product of odd spheres. Eilenberg--Zilber reduces the negative cyclic complex to a tensor-product mixed complex $(W, B^\otimes) = \bigotimes_i (V_i, B_i)$ with single-factor input $H_j(V_i, B_i) = \Z/j$ for $j \ge 1$. Iterated K\"unneth produces gcd-indexed cyclic torsion with binomial multiplicities, and the kernel of $B^\otimes$ has rank generating function
\[
K(t) \;=\; \frac{(1 - t)^r + 2^r t}{(1 + t)(1 - t)^r}.
\]
The Borel spectral sequence for $LX$ collapses at $E_3$ integrally with no extensions. Time permitting, I will indicate a degree-$D_G$ naturality identity transporting this to compact Lie groups via the Hurewicz-scaled map $\varphi_G: X_G \to G$.

Thursday, 04 June 2026
Time Speaker Title Resources
09:30 to 11:00 Katherine Poirier (CUNY, New York, USA) String Topology and Moduli Space Operations (Lecture 3)
  • Chas–Sullivan loop product (chain/homology level)
  • Cohen–Godin operations via fatgraphs
  • Moduli space operations
  • Compactifications and higher structures
     
11:30 to 13:00 Christian Ausoni (University of Paris, France) The Telescope Conjecture
  • The statement of the Telescope conjecture;
  • The disproof at height 2;
  • Some open questions.
     
14:30 to 15:30 Ayelet Lindenstrauss (Indiana University, Bloomington, USA) Equivariant Spectra, Mackey Functors, and Tambara Functors

We will start with an explanation of what a genuine G-spectrum is for G an finite group. We will then discuss Mackey functors, which encapsulate the structure we get on equivariant \pi_0 of such a spectrum, and Tambara functors, which encapsulate the structure of the equivariant \pi_0 of a genuine commutative G-ring spectrum. Both turn out to occur in other kinds of mathematics as well.

16:00 to 17:00 Akashdwip Biswas (ISI Kolkata, India) EO-Theories of Complex Projective Spaces

In this talk we will present some results on real and higher real K-theories of complex projective spaces, \(KO_*(\mathbb{CP}^n)\), and \(EO_{p-1}^*(\mathbb{CP}^n)\) for odd primes \(p\). We will give a brief review of the cohomology theories \(EO_{p-1}\) and discuss the methods involved, including the filtration spectral sequence and the homotopy fixed point spectral sequence. Finally, using these computations, we will discuss various applications concerning exotic smooth structures on complex projective spaces, the existence of free smooth \(S^1\) and \(S^3\)-actions on exotic spheres, and the existence of complex hyperbolic manifolds with certain curvature properties.

Friday, 05 June 2026
Time Speaker Title Resources
09:30 to 11:00 Ayelet Lindenstrauss (Indiana University, Bloomington, USA) Equivariant Loday Constructions

If we have a genuine commutative G-ring spectrum, we can take its Loday construction over a G-simplicial set, so then the group G acts both on the underlying simplicial set and on the `coefficients'. We will discuss some known constructions in this framework, and connect back to crossed simplicial groups.

11:30 to 13:00 Katherine Poirier (CUNY, New York, USA) String Topology and Moduli Space Operations (Lecture 4)
  • Chas–Sullivan loop product (chain/homology level)
  • Cohen–Godin operations via fatgraphs
  • Moduli space operations
  • Compactifications and higher structures