nLab rational parameterized stable homotopy theory



Rational homotopy theory

Stable Homotopy theory

Homological algebra

homological algebra

(also nonabelian homological algebra)



Basic definitions

Stable homotopy theory notions



diagram chasing

Schanuel's lemma

Homology theories


under construction



It is a classical fact that the rationalization of classical homotopy theory (of topological spaces or simplicial sets) – called rational homotopy theory – is considerably more tractable than general homotopy theory, as exhibited by the existence of small concrete dg-algebraic models for rational homotopy types: minimal Sullivan algebras or equivalently their dual dg-coalgebras. A similar statement holds for the rationalization of stable homotopy theory i.e. the homotopy theory of spectra (of topological spaces or simplicial sets): rational spectra are equivalent to rational chain complexes, i.e. to dg-modules over \mathbb{Q}. This is a dg-model for rational stable homotopy theory compatible with that of classical rational homotopy theory in tat the stabilization adjunction that connects classical homotopy theory to stable homotopy theory is, under these identifications, modeled by the forgetful functor from dg-(co-)algebras to chain complexes

classical homotopy theory stable homotopy theory spaces Σ Ω spectra stabilization rationally dg(co)algebras underlyingfree chain complexes \array{ & \text{classical homotopy theory} && \text{stable homotopy theory} \\ & spaces & \underoverset{\underset{\Sigma^\infty}{\longrightarrow}}{\overset{\Omega^\infty}{\longleftarrow}}{} & spectra \\ & & \text{stabilization} \\ \text{rationally} & \text{dg(co)algebras} & \underoverset{\underset{underlying}{\longrightarrow}}{\overset{free}{\longleftarrow}}{} & \text{chain complexes} }

Classical homotopy theory and stable homotopy theory are unified and jointly generalized in parameterized stable homotopy theory, whose objects are parameterized spectra, parameterized over a classical homotopy type. The rational parameterized stable homotopy theory to be discussed here is supposed to be the rationalization of this joint generalization, unifiying and jointly generalizing the algebraic model of rational topological spaces by Sullivan algebras and of HH \mathbb{Q}-module spectra by chain complexes.

stable homotopy theory parameterized stable homotopy theory classical homotopy theory spectra include parameterized spectra project spaces include project rationally chain complexes include dg-modules project dg(co)algebras \array{ & \text{stable homotopy theory} && \text{parameterized stable homotopy theory} && \text{classical homotopy theory} \\ & \text{spectra} &\overset{\phantom{\text{include}}}{\longrightarrow}& \text{parameterized spectra} &\overset{\phantom{\text{project}}}{\longrightarrow}& \text{spaces} \\ & &\text{include}& &\text{project}& \\ \text{rationally} & \text{chain complexes} &\overset{\phantom{\text{include}}}{\longrightarrow}& \text{dg-modules} &\overset{\phantom{\text{project}}}{\longrightarrow}& \text{dg(co)algebras} }

Here we (intend to) show that, accordingly, rational parameterized homotopy theory is presented by the the opposite of the homotopical category of dg-modules over cochain differential graded-commutative algebras in non-negative degrees.

under construction


Chain complexes



For nn \in \mathbb{N} write

  • Ch n,Ch ,Ch_{\geq n, \mathbb{Q}} \hookrightarrow Ch_{\bullet,\mathbb{Q}} for the full subcategory of the chain complexes concentrated in degree n\geq n;

  • Ch nCh Ch^{\geq n}_{\mathbb{Q}} \hookrightarrow Ch^\bullet_{\mathbb{Q}} for the full subcategory of the cochain complexes concentrated in degree n\geq n.

For VModV \in \mathbb{Q} Mod a rational vector space, and for nn \in \mathbb{N}, we write V[n]V[n] both for the chain complex as well as for the cochain complex concentrated on VV in degree nn.



Write dgcAlg 𝕢 0dgcAlg^{\geq 0}_{\mathbb{q}} for the category of cochain dgc-algebras over the rational numbers concentrated in non-negative degrees.

Say that a morphism in this category is

  1. a weak equivalence if it is a quasi-isomorphisms on the underlying chain complexes;

  2. a fibration if it is degreewise surjection;

  3. a cofibration it it is a relative Sullivan algebra inclusion,

We write

(dgcAlg 0) proj (dgcAlg^{\geq 0}_{\mathbb{Q}})_{proj}

for the category dgcAlg 0dgcAlg^{\geq 0}_{\mathbb{Q}} equipped with these three classes of morphisms.


The homotopical category (dgcAlg 0) proj(dgcAlg^{\geq 0}_{\mathbb{Q}})_{proj} from def. is a model category, to be called the projective model structure on dgc-algebras in non-negative degrees.

(Bousfield-Gugenheim 76, theorem 4.3)


For SsSetS \in sSet a simplicial set, write

Ω poly (S)dgcAlg 0 \Omega^\bullet_{poly}(S) \in dgcAlg^{\geq 0}_{\mathbb{Q}}

for the polynomial differential forms with rational coefficients on SS.

(Bousfield-Gugenheim 76, def. 2.1)


Write [0]([0],d=0)\mathbb{Q}[0] \coloneqq (\mathbb{Q}[0], d = 0) for the dgc-algebra concentrated on the ground field in degree 0, necessarily with vanishing differential. This is the initial object in dgcAlg 0dgcAlg^{\geq 0}_{\mathbb{Q}}.


(dgcAlg 0) /[0] (dgcAlg^{\geq 0}_{\mathbb{Q}})_{/\mathbb{Q}[0]}

for the slice category of that of all dgc-algebras (def. ) over [0]\mathbb{Q}[0]. Hence an object in this category is a pair consisting of a dgc-algebra AA and a dg-algebra homomorphism of the form

ϵ A:A[0]. \epsilon_A \;\colon\; A \longrightarrow \mathbb{Q}[0] \,.

This is equivalently called a [0]\mathbb{Q}[0]-augmented dgc-algebra. The kernel of the augmentation map ϵ\epsilon

ker ϵ ACh 0 ker_{\epsilon_{A}} \in Ch^{\geq 0}_{\mathbb{Q}}

is the augmentation ideal of (A,ϵ)(A,\epsilon).

Since [0]dgcAlg 0\mathbb{Q}[0] \in dgcAlg^{\geq 0}_{\mathbb{Q}} carries a unique augmentation ϵ=id\epsilon = id, we still write [0]\mathbb{Q}[0] for the ground field regarded as an augmented dgc-algebra. As such this is now a zero object.

Furthermore write

((dgcAlg 0) /[0]) proj \left( (dgcAlg^{\geq 0}_{\mathbb{Q}})_{/\mathbb{Q}[0]} \right)_{proj}

for the slice model structure induced on this by the projective model structure on dgc-algebras according to prop. .

See also Bousfield-Gugenheim 76, 4.11

Simplicial Lie algebras

(LieAlg k) proj Δ opNN *(dgLieAlg k) projCEdgcoAlg k (LieAlg_k)^{\Delta^{op}}_{proj} \underoverset {\underset{N}{\longrightarrow}} {\overset{N^\ast}{\longleftarrow}} {\bot} (dgLieAlg_k)_{proj} \underoverset {\underset{CE}{\longrightarrow}} {\overset{\mathcal{L}}{\longleftarrow}} {\bot} dgcoAlg_k



We want to claim the following:

For every 𝔤(LieAlg ) Δ op\mathfrak{g} \in (LieAlg_{\mathbb{Q}})^{\Delta^{op}} there is a Quillen equivalence

SeqSpec(𝔤Mod) stable QuSeqSpec((Sym) op)SeqSpec(ker ϵ() op)SeqSpec(𝔤/(LieAlg ) Δ op/𝔤) stable SeqSpec\left( \mathfrak{g}Mod \right)_{stable} \underoverset {\underset{SeqSpec((Sym)^{op})}{\longrightarrow}} { \overset{SeqSpec( ker_{\epsilon(-)}^{op} )}{\longleftarrow} } {\simeq_{Qu}} SeqSpec\left( \mathfrak{g} / (LieAlg_{\mathbb{Q}})^{\Delta^{op}} / \mathfrak{g} \right)_{stable}

Idea of proof: the analogous statement for simplicial Lie algebras replaced by rational simplicial algebras cAlg 𝔸 Δ opcAlg_{\mathbb{A}}^{\Delta^{op}} is Schwede 97, theorem 3.2.3. Apart from the connectivity of the SymSym-construction, all that this proof uses is that simplicial commutative algebras form a right proper simplicial model category. But also the model structure on simplicial Lie algebras is right proper and simplicial.


A classical reference on plain rational homotopy theory is:

The equivalence between HRH R-module spectra (unparametrized) and RR-chain complexes is due to

  • Stefan Schwede, section 3 of Spectra in model categories and applications to the algebraic cotangent complex, Journal of Pure and Applied Algebra 120 (1997) 104 (pdf)

  • Brooke Shipley, HH \mathbb{Z}-algebra spectra are differential graded algebras , Amer. Jour. of Math. 129 (2007) 351-379. (arXiv:math/0209215)

Discussion of rational fiberwise suspension spectra:

A discussion of full-blown rational parametrized stable homotopy theory is due to

Application to mathematical analysis of duality between M-theory and type IIA string theory:

Last revised on April 7, 2023 at 12:42:45. See the history of this page for a list of all contributions to it.