chromatic homotopy theory

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chromatic homotopy theory

See tensor triangular geometry. attachments/Pasted%20image%2020220508204755.png attachments/Pasted%20image%2020220419150128.png

The chromatic view-point, which studies stable homotopy theory via its relationships to the moduli of formal groups, and related topics such as topological modular forms, use a sizable amount of (fairly abstract) algebraic geometry. And Lurie’s work on derived algebraic geometry was motivated in part by establishing foundations adequate to the task of defining equivariant forms of topological modular forms.

Kervaire and Milnor defined \(\Theta_n\) to be the group of homotopy spheres up to h-cobordism (where the group operation is given by connect sum).

By the h-cobordism theorem (\(n > 4\)) and Perelman’s proof of the Unsorted/Poincare conjectures (\(n = 3\)).

For \(n \neq 4\), \(\Theta_n = 0\) if and only if \(S^n\) has a unique smooth structure (i.e. there are no exotic spheres of dimension \(n\)).

We wish to consider the following question: For which \(n\) is \(\Theta_n = 0\)? The general belief is that there should be finitely many such \(n\), and these n should be concentrated in relatively low dimensions.

Relation to complex cobordism, complex oriented cohomology theories, and FGLs via the Landweber exact functor theorem. attachments/Pasted%20image%2020220508194119.png

See Morava E theory, Morava K theory, thick subcategory, tmf.

Relation to stacks: attachments/Pasted%20image%2020220508194333.png

The chromatic tower

Fix a prime \(p\) the chromatic tower of a Thom spectrum \(X\) is the tower of Bousfield localization: \begin{align*} X \rightarrow \cdots \rightarrow X _ { E ( n ) } \rightarrow X _ { E ( n - 1 ) } \rightarrow \cdots \rightarrow X _ { E ( 0 ) } \end{align*} where \(E(n)\) is the \(n\)th Johnson-Wilson spectrum \((E(0) = { \mathsf{H} }{\mathbf{Q}}\), by convention) with \begin{align*} E ( n ) _ { * } = \mathbb { Z } _ { ( p ) } \left[ v _ { 1 } , \dots , v _ { n - 1 } , v _ { n } ^ { \pm } \right] \end{align*} The fibers of the chromatic tower \begin{align*} M _ { n } X \rightarrow X _ { E ( n ) } \rightarrow X _ { E ( n - 1 ) } \end{align*} are called the monochromatic layers.

The spectral sequence associated to the chromatic tower is the chromatic spectral sequence \begin{align*} E _ { 1 } ^ { n , * } = \pi _ { * } M _ { n } X \Rightarrow \pi _ { * } X{ \scriptsize {}_{ \left[ { \scriptstyle { {p}^{-1}} } \right] } } \end{align*}

Let \(M_\ell\) denote the DM moduli stack of elliptic curves over \(\operatorname{Spec}({\mathbf{Z}})\).

For a commutative ring \(R\), the groupoid of \(R\)-points of \(M_\ell\) is the groupoid of elliptic curves over \(R\). This Unsorted/stacks MOC carries a line bundle \(\omega\) where for an elliptic curve \(C\), the fiber over \(C\) is given by \(\omega C = T^∗_e C,\) the tangent space of \(C\) at its basepoint \(e\).

The stack \(M_{\ell}\) admits a compactification \({ \mathcal{M}_{\mathrm{ell}} }\) whose \(R\) points are generalized elliptic curves. The space of integral modular forms of weight \(k\) is defined to be the space of sections \begin{align*} H ^ { 0 } \left( \mkern 1.5mu\overline{\mkern-1.5mu{ \mathcal{M}_{\mathrm{ell}} }\mkern-1.5mu}\mkern 1.5mu; \omega{ {}^{ \scriptscriptstyle\otimes_{k}^{n} } } \right) \end{align*} Motivated by the definition of integral modular forms and the descent spectral sequence in the case of \(U = M_\ell\) , the spectrum $\mathrm{TMF} $ (see TMF) is defined to be its global sections: \begin{align*} \mathrm{TMF} \coloneqq{\mathcal{O}}^ { {\mathsf{Top}}} \left( \mkern 1.5mu\overline{\mkern-1.5mu{ \mathcal{M}_{\mathrm{ell}} }\mkern-1.5mu}\mkern 1.5mu \right) \end{align*}

Chromatic convergence

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Can be done on a thick subcategory: attachments/Pasted%20image%2020220508190152.png

Chromatic filtration

An application to K-theory: attachments/Pasted%20image%2020220209211652.png

The thick subcategory and nilpotent theorems

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Relation to tensor triangular geometry and tmf

See tensor triangular geometry and tmf. Explaining the infamous chromatic stratification picture: attachments/Pasted%20image%2020220508205207.png attachments/Pasted%20image%2020220508205136.png attachments/Pasted%20image%2020220508205057.png

Applications

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