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\newtheorem{prop}{Proposition} \newtheorem{cor}{Corollary} \newtheorem*{utheorem}{Theorem} \newtheorem*{ulemma}{Lemma} \newtheorem*{uprop}{Proposition} \newtheorem*{ucor}{Corollary} \theoremstyle{definition} \newtheorem{defn}{Definition} \newtheorem{example}{Example} \newtheorem*{udefn}{Definition} \newtheorem*{uexample}{Example} \theoremstyle{remark} \newtheorem{remark}{Remark} \newtheorem{note}{Note} \newtheorem*{uremark}{Remark} \newtheorem*{unote}{Note} %------------------------------------------------------------------- \begin{document} %------------------------------------------------------------------- \section*{Morava K-theory} \hypertarget{context}{}\subsubsection*{{Context}}\label{context} \hypertarget{cohomology}{}\paragraph*{{Cohomology}}\label{cohomology} [[!include cohomology - contents]] \hypertarget{stable_homotopy_theory}{}\paragraph*{{Stable Homotopy theory}}\label{stable_homotopy_theory} [[!include stable homotopy theory - contents]] \hypertarget{higher_algebra}{}\paragraph*{{Higher algebra}}\label{higher_algebra} [[!include higher algebra - contents]] \hypertarget{morava_ktheory}{}\section*{{Morava K-theory}}\label{morava_ktheory} \noindent\hyperlink{idea}{Idea}\dotfill \pageref*{idea} \linebreak \noindent\hyperlink{definition}{Definition}\dotfill \pageref*{definition} \linebreak \noindent\hyperlink{construction_from_complex_cobordism}{Construction from complex cobordism}\dotfill \pageref*{construction_from_complex_cobordism} \linebreak \noindent\hyperlink{axiomatic_characterization}{Axiomatic characterization}\dotfill \pageref*{axiomatic_characterization} \linebreak \noindent\hyperlink{properties}{Properties}\dotfill \pageref*{properties} \linebreak \noindent\hyperlink{universal_characterization}{Universal characterization}\dotfill \pageref*{universal_characterization} \linebreak \noindent\hyperlink{ring_structure}{Ring structure}\dotfill \pageref*{ring_structure} \linebreak \noindent\hyperlink{AsInfinityFields}{As $A_\infty$-fields}\dotfill \pageref*{AsInfinityFields} \linebreak \noindent\hyperlink{as_the_primes_in_the_category_of_spectra}{As the primes in the $\infty$-category of spectra}\dotfill \pageref*{as_the_primes_in_the_category_of_spectra} \linebreak \noindent\hyperlink{relation_to_chromatic_homotopy_theory}{Relation to chromatic homotopy theory}\dotfill \pageref*{relation_to_chromatic_homotopy_theory} \linebreak \noindent\hyperlink{relation_to_bousfield_lattice}{Relation to Bousfield lattice}\dotfill \pageref*{relation_to_bousfield_lattice} \linebreak \noindent\hyperlink{Orientation}{Orientation}\dotfill \pageref*{Orientation} \linebreak \noindent\hyperlink{group_rings_and_twists}{$\infty$-Group rings and twists}\dotfill \pageref*{group_rings_and_twists} \linebreak \noindent\hyperlink{related_concepts}{Related concepts}\dotfill \pageref*{related_concepts} \linebreak \noindent\hyperlink{references}{References}\dotfill \pageref*{references} \linebreak \hypertarget{idea}{}\subsection*{{Idea}}\label{idea} For each [[prime]] $p$, the Morava K-theories are a tower $\{K(n)\}_{n \in \mathbb{N}}$ of [[complex oriented cohomology theories]] whose [[coefficient]] [[ring]] is \begin{displaymath} \pi_\bullet\left(K\left(n\right)\right) \simeq \mathbb{F}_p [v_n, v_n^{-1}] \end{displaymath} where $v_n$ is in degree $2(p^n-1)$. Hence with $p = 2$ for $n = 1$ $v_1$ is a [[Bott element]] of degree 2 and $K(1)$ is closely related to [[complex K-theory]], while for $n= 2$ $v_2$ is then a [[Bott element]] of degree 6 and $K(2)$ is closely related to [[elliptic cohomology]]. There is also [[integral Morava K-theory]] which instead has coefficient ring \begin{displaymath} \pi_\bullet\left(K\left(n\right)\right) \simeq \mathbb{Z}_{(p)} [v_n, v_n^{-1}] \,, \end{displaymath} where $\mathbb{Z}_{(p)}$ is the [[localization]] of the integers at the given [[prime]]. Integral Morava K-theory can be obtained as a localization of a quotient $MU/I$ of [[complex cobordism cohomology theory]] $MU$ (\hyperlink{Buhne11}{Buhn\'e{} 11}). \hypertarget{definition}{}\subsection*{{Definition}}\label{definition} We need the following standard notation throughout this entry. \begin{defn} \label{}\hypertarget{}{} For $p \in \mathbb{N}$ a [[prime number]], we write \begin{itemize}% \item $\mathbb{F}_p = \mathbb{Z}/(p)$ for the [[field]] with $p$ elements; \item $\mathbb{Z}_{(p)}$ for the [[localization of a ring|localization ring]] of the [[integers]] at $p$; \item $\mathbb{Z}_p$ for the [[p-adic integers]]. \end{itemize} \end{defn} \hypertarget{construction_from_complex_cobordism}{}\subsubsection*{{Construction from complex cobordism}}\label{construction_from_complex_cobordism} (e.g. \hyperlink{LurieLecture}{Lurie 10, lecture 22, def. 5}) \hypertarget{axiomatic_characterization}{}\subsubsection*{{Axiomatic characterization}}\label{axiomatic_characterization} \begin{prop} \label{}\hypertarget{}{} For each [[prime number|prime integer]] $p$ there exists a sequence of [[multiplicative cohomology theory|multiplicative]] [[generalized cohomology theories|generalized cohomology]]/[[generalized homology theories|homology theories]] \begin{displaymath} \{K(n)\}_{n \in \mathbb{N}} \end{displaymath} with the following properties: \begin{enumerate}% \item $K(0)_\ast(X)=H_\ast(X;\mathbb{Q})$ and $\overline{K(0)}_\ast(X)=0$ when $\overline{H}_\ast(X)$ is all [[torsion]]. \item $K(1)_\ast(X)$ is one of $p-1$ isomorphic summands of mod-$p$ complex [[topological K-theory]]. \item $K(0)_\ast(pt.)=\mathbb{Q}$ and for $n\neq 0$, $K(n)_\ast(pt.)=\mathbb{F}_p[v_n,v_n^{-1}]$ where $\vert v_n\vert=2p^n-2$. (This [[ring]] is a graded [[field]] in the sense that every graded [[module]] over it is [[free module|free]]. $K(n)_\ast(X)$ is a module over $K(n)_\ast(pt.)$, see \hyperlink{AsInfinityFields}{below}) \item There is a [[Künneth isomorphism]]: $K(n)_\ast(X\times Y)\cong K(n)_\ast(X)\otimes_{K(n)_\ast(pt.)}K(n)_\ast(Y).$ \item Let $X$ be a p-local finite [[CW-complex]]. If $\overline{K(n)}_\ast(X)$ vanishes then so does $\overline{K(n-1)}_\ast(X)$. \item If $X$ as above is not contractible then $\overline{K(n)}_\ast(X)=K(n)_\ast(pt.)\otimes \overline{H}_\ast(X;\mathbb{Z}/(p))$. \end{enumerate} These are called the \emph{Morava K-theories}. \end{prop} Due to the third point one may regard $K(n)$ as a [[∞-field]] among the [[A-infinity rings]]. See \hyperlink{AsInfinityFields}{below}. \hypertarget{properties}{}\subsection*{{Properties}}\label{properties} \hypertarget{universal_characterization}{}\subsubsection*{{Universal characterization}}\label{universal_characterization} \begin{prop} \label{}\hypertarget{}{} For each [[prime number]] $p$ and each $n \in \mathbb{N}$, the Morava K-theory $K(n)$ is, up to [[equivalence in an (∞,1)-category|equivalence]], the unique [[spectrum]] underlying an [[H-space|homotopy associative]] spectrum which is \begin{enumerate}% \item [[complex oriented cohomology theory|complex oriented]]; \item whose [[formal group]] has [[height of a formal group|height]] exactly $n$; \item whose [[homotopy groups]] are $\pi_\bullet \simeq \mathbb{F}_p[v_n^\pm]$. (with $v_n$ defined as at \emph{[[height of a formal group|height]]}). \end{enumerate} \end{prop} For instance (\hyperlink{LurieLecture}{Lurie, lecture 24, prop. 11}). \hypertarget{ring_structure}{}\subsubsection*{{Ring structure}}\label{ring_structure} \begin{prop} \label{}\hypertarget{}{} $K(n)$ admits the structure of an [[A-∞ algebra]], in fact of an $MU_{(p)}$-[[A-∞ algebra]]. \end{prop} Due to Robinson (and [[Andrew Baker]] at $p = 2$). (See e.g. \hyperlink{LurieLecture}{Lurie 10, lecture 22, lemma 2}) \begin{remark} \label{}\hypertarget{}{} With the exception of the extreme case of $n=0$, the fields $K(n)$ do not admit [[E-∞-ring]] multiplicative structures. However, when $p\neq 2$, the multiplication is homotopy commutative. For $p = 2$ it is \emph{not} even homotopy commutative. Nevertheless, for many spaces $X$, the $K(n)$-[[generalized (Eilenberg-Steenrod) cohomology|generalized cohomology]] at the prime $2$ of $X$ forms a commutative ring. \end{remark} (e.g. \hyperlink{LurieLecture}{Lurie 10, lecture 22, warning 6}) \hypertarget{AsInfinityFields}{}\subsubsection*{{As $A_\infty$-fields}}\label{AsInfinityFields} \begin{prop} \label{}\hypertarget{}{} If $E$ is an [[∞-field]] then $E \otimes K(n) \neq 0$ and $E$ admits the structure of a $K(n)$-[[module spectrum|module]]. \end{prop} This appears for instance as (\hyperlink{LurieLecture}{Lurie, lecture 24, prop. 9, remark 13}) \begin{remark} \label{}\hypertarget{}{} This means that the Morava $A_\infty$-rings $K(n)$ are essentially the only [[∞-fields]] in the [[stable homotopy category]]. \end{remark} See (\hyperlink{LurieLecture}{Lurie, lecture 24, remark 13}) \hypertarget{as_the_primes_in_the_category_of_spectra}{}\subsubsection*{{As the primes in the $\infty$-category of spectra}}\label{as_the_primes_in_the_category_of_spectra} The Morava K-theories label the [[prime spectrum of a symmetric monoidal stable (∞,1)-category]] of the [[(∞,1)-category of spectra]] for [[p-localization|p-local]] and [[finite spectra]] . This is the content of the \emph{[[thick subcategory theorem]]}. \hypertarget{relation_to_chromatic_homotopy_theory}{}\subsubsection*{{Relation to chromatic homotopy theory}}\label{relation_to_chromatic_homotopy_theory} The layers in the [[chromatic homotopy theory|chromatic tower]] capture periodic phenomena in [[stable homotopy theory]], corresponding to the Morava K-theory $E_\infty$-fields. Specifically the [[Bousfield localization of spectra]] $L_{K(n)}$ acts on [[complex oriented cohomology theories]] like completion along the locally closed substack \begin{displaymath} \mathcal{M}^n_{FG} \hookrightarrow \mathcal{M}_{FG} \end{displaymath} of the [[moduli stack of formal groups]] at those of [[height of a formal group|height]] $n$. (\hyperlink{LurieLecture}{Lurie 10, lecture 29}) [[!include chromatic tower examples - table]] \hypertarget{relation_to_bousfield_lattice}{}\subsubsection*{{Relation to Bousfield lattice}}\label{relation_to_bousfield_lattice} It is known that in the [[Bousfield lattice]] of the [[stable homotopy category]], the Bousfield classes of the Morava K-theories are minimal. It is conjectured by [[Mark Hovey]] and John Palmieri that the [[Boolean algebra]] contained in the Bousfield lattice is atomic and generated by the Morava K-theories and the spectra $A(n)$ which measure the failure of the [[telescope conjecture]]. \hypertarget{Orientation}{}\subsubsection*{{Orientation}}\label{Orientation} The [[orientation in generalized cohomology|orientation]] of [[integral Morava K-theory]] is discussed in (\hyperlink{SatiKriz04}{Sati-Kriz 04}, \hyperlink{Buhne11}{Buhn\'e{} 11}). It is essentially given by the vanishing of the seventh [[integral Stiefel-Whitney class]] $W_7$. Notice that this is in higher analogy to how [[orientation in generalized cohomology|orientation]] in [[complex K-theory]] is given by the vanishing third [[integral Stiefel-Whitney class]] $W_3$ ([[spin{\tt \symbol{94}}c-structure]]). \hypertarget{group_rings_and_twists}{}\subsubsection*{{$\infty$-Group rings and twists}}\label{group_rings_and_twists} Write $gl_1(K(n))$ for the [[∞-group of units]] of the (a) Morava K-theory spectrum \begin{prop} \label{}\hypertarget{}{} For $p = 2$ and all $n \in \mathbb{N}$, there is an [[equivalence in an (infinity,1)-category|equivalence]] \begin{displaymath} Maps(B^{n+1}U(1), B gl_1(K(n))) \simeq \mathbb{Z}_2 \end{displaymath} between \begin{itemize}% \item the [[mapping space]] from the [[classifying space]] for [[circle n-bundle|circle (n+1)-bundles]] to the [[delooping]] of the [[∞-group of units]] of $K(n)$ \end{itemize} and \begin{itemize}% \item the [[p-adic integers|2-adic integers]]. \end{itemize} \end{prop} (\hyperlink{SatiWesterland11}{Sati-Westerland 11, theorem 1}) \begin{remark} \label{}\hypertarget{}{} By the discussion at [[(∞,1)-vector bundle]] this means that for each such map there is a type of [[twisted cohomology|twist]] of Morava K-theory (at $p = 2$). \end{remark} \hypertarget{related_concepts}{}\subsection*{{Related concepts}}\label{related_concepts} \begin{itemize}% \item [[equivariant Morava K-theory]] \item [[2-periodic Morava K-theory]] \item [[K-theory]], [[topological K-theory]], [[algebraic K-theory]] \item [[chromatic homotopy theory]] \item [[K(n)-local stable homotopy theory]] \item [[integral Morava K-theory]] \item [[Morava E-theory]] \begin{itemize}% \item [[Lubin-Tate theory]] \end{itemize} \end{itemize} \hypertarget{references}{}\subsection*{{References}}\label{references} Morava K-theory originates in unpublished preprints by [[Jack Morava]] in the early 1970s. A first published account appears in \begin{itemize}% \item David Copeland Johnson, ; W. Stephen Wilson, \emph{BP operations and Morava's extraordinary K-theories.}, Math. Z. 144 (1): 55$-$75, (1975) \end{itemize} see also \begin{itemize}% \item [[Doug Ravenel]], \emph{Nilpotence and Periodicity in Stable Homotopy Theory}, Annals of Mathematics Studies 128, Princeton University Press (1992). \end{itemize} A discussion with an eye towards [[category theory|category theoretic]] general abstract properties of localized stable homotopy theory is in \begin{itemize}% \item [[Mark Hovey]], [[Neil Strickland]], \emph{Morava K-theories and localization}, American Mathematical Soc., Jan 1, 1999 (\href{http://www.math.rochester.edu/people/faculty/doug/otherpapers/kn.pdf}{pdf}) \end{itemize} A survey of the theory is in \begin{itemize}% \item Urs W\"u{}rgler, \emph{Morava K-theories: a survey}, Algebraic topology Poznan 1989, Lecture Notes in Math. 1474, Berlin: Springer, pp. 111 138 (1991) \end{itemize} In \begin{itemize}% \item [[Jacob Lurie]], \emph{[[Chromatic Homotopy Theory]]} Lecture notes, (\href{http://www.math.harvard.edu/~lurie/252xnotes/Lecture22.pdf}{pdf}) Lecture 22 \emph{Morava E-theory and Morava K-theory} (\href{http://www.math.harvard.edu/~lurie/252xnotes/Lecture22.pdf}{pdf}) Lecture 23 \emph{The Bousfield Classes of $E(n)$ and $K(n)$} (\href{http://www.math.harvard.edu/~lurie/252xnotes/Lecture23.pdf}{pdf}) Lecture 24 \emph{Uniqueness of Morava K-theory} (\href{http://www.math.harvard.edu/~lurie/252xnotes/Lecture24.pdf}{pdf}) \end{itemize} the explicit definition via [[formal group laws]] is in lecture 22 and the abstract characterization in lecture 24. The $E_\infty$-algebra structure over $\widehat{E(n)}$ is comment on in \begin{itemize}% \item [[Andrew Baker]], \emph{Brave new Hopf algebroids} (\href{http://www.maths.gla.ac.uk/~ajb/dvi-ps/brave-ha.pdf}{pdf}) \end{itemize} based on \begin{itemize}% \item [[Neil Strickland]], \emph{Products on $MU$-modules}, Trans. Amer. Math. Soc. 351 (1999), 2569-2606. \end{itemize} The [[orientation in generalized cohomology|orientation]] of [[integral Morava K-theory]] is discussed in \begin{itemize}% \item [[Igor Kriz]], [[Hisham Sati]], \emph{M-theory, type IIA superstrings, and elliptic cohomology}, Adv. Theor. Math. Phys. 8 (2004), no. 2, 345--394 (\href{http://arxiv.org/abs/hep-th/0404013}{arXiv:hep-th/0404013}) \end{itemize} \begin{itemize}% \item [[Lukas Buhné]], \emph{[[Properties of Integral Morava K-Theory and the Asserted Application to the Diaconescu-Moore-Witten Anomaly]]}, Diploma thesis Hamburg (2011) \end{itemize} Some [[twisted cohomology|twists]] of Morava K-theory/maps into its [[∞-group of units]] as well as the [[Atiyah-Hirzebruch spectral sequence]] for Morava $K$ and Morava $E$ are discussed in \begin{itemize}% \item [[Hisham Sati]], [[Craig Westerland]], \emph{Twisted Morava K-theory and E-theory} (\href{http://arxiv.org/abs/1109.3867}{arXiv:1109.3867}) \end{itemize} For a review in the context of [[M-theory]] see \begin{itemize}% \item [[Hisham Sati]], \emph{[[Geometric and topological structures related to M-branes]]} (2010) \end{itemize} [[!redirects Morava K-theories]] \end{document}